Wednesday, January 30, 2008
Total urban population in India has increased more than ten times from 26 million in 1901 to 285 million in 2001 whereas total population has increased less than five times from 238 million to 1027 million from 1901 to 2001 respectively. In the same fashion the number of town had also increased from 1916 in 1901 to 2422 in 1951 and then to 4689 in 1991. About three-fold increase has been noticed for percentage of total urban population in Class-I city over the decades (1901 to 1991). While there was only one million plus city (Kolkata) in 1901 in
Tuesday, January 29, 2008
These systems promise radical improvements to many systems that impact all people. By combining GPS with current and future computer mapping techniques, we will be better able to identify and manage our natural resources. Intelligent vehicle location and navigation systems will let us avoid congested freeways and find more efficient routes to our destinations, saving millions of dollars in gasoline and tons of air pollution. Travel abord ships and aircraft will be safer in all weather conditions. Businesses with large amounts of outside plant (railroads, utilities) will be able to manage their resources more efficiently, reducing consumer costs.
Most naturally occurring earthquakes are related to the tectonic nature of the Earth. Such earthquakes are called tectonic earthquakes. The Earth's lithosphere is a patchwork of plates in slow but constant motion caused by the release to space of the heat in the Earth's mantle and core. The heat causes the rock in the Earth to flow on geological timescales, so that the plates move slowly but surely. Plate boundaries lock as the plates move past each other, creating frictional stress. When the frictional stress exceeds a critical value, called local strength, a sudden failure occurs. The boundary of tectonic plates along which failure occurs is called the fault plane. When the failure at the fault plane results in a violent displacement of the Earth's crust, energy is released as a combination of radiated elastic strain seismic waves, frictional heating of the fault surface, and cracking of the rock, thus causing an earthquake. This process of gradual build-up of strain and stress punctuated by occasional sudden earthquake failure is referred to as the Elastic-rebound theory. It is estimated that only 10 percent or less of an earthquake's total energy is radiated as seismic energy. Most of the earthquake's energy is used to power the earthquake fracture growth or is converted into heat generated by friction. Therefore, earthquakes lower the Earth's available elastic potential energy and raise its temperature, though these changes are negligible compared to the conductive and convective flow of heat out from the Earth's deep interior.
The majority of tectonic earthquakes originate at depths not exceeding tens of kilometers. In subduction zones, where older and colder oceanic crust descends beneath another tectonic plate, Deep focus earthquakes may occur at much greater depths (up to seven hundred kilometers). These seismically active areas of subduction are known as Wadati-Benioff zones. These are earthquakes that occur at a depth at which the subducted lithosphere should no longer be brittle, due to the high temperature and pressure. A possible mechanism for the generation of deep focus earthquakes is faulting caused by olivine undergoing a phase transition into a spinel structure.
Earthquakes also often occur in volcanic regions and are caused there, both by tectonic faults and by the movement of magma in volcanoes. Such earthquakes can serve as an early warning of volcanic eruptions.
Sometimes a series of earthquakes occur in a sort of earthquake storm, where the earthquakes strike a fault in clusters, each triggered by the shaking or stress redistribution of the previous earthquakes. Similar to aftershocks but on adjacent segments of fault, these storms occur over the course of years, and with some of the later earthquakes as damaging as the early ones. Such a pattern was observed in the sequence of about a dozen earthquakes that struck the North Anatolian Fault in
At the Earth's surface, earthquakes manifest themselves by a shaking and sometimes displacement of the ground. When a large earthquake epicenter is located offshore, the seabed sometimes suffers sufficient displacement to cause a tsunami. The shaking in earthquakes can also trigger landslides and occasionally volcanic activity.
In its most generic sense, the word earthquake is used to describe any seismic event—whether a natural phenomenon or an event caused by humans—that generates seismic waves. Earthquakes are caused mostly by rupture of geological faults, but also by volcanic activity, landslides, mine blasts, and nuclear experiments.
An earthquake's point of initial rupture is called its focus or hypocenter. The term epicenter means the point at ground level directly above this.
Synthetic aperture radar technology has provided terrain structural information to geologists for mineral exploration, oil spill boundaries on water to environmentalists, sea state and ice hazard maps to navigators, and reconnaissance and targeting information to military operations. There are many other applications or potential applications. Some of these, particularly civilian, have not yet been adequately explored because lower cost electronics are just beginning to make SAR technology economical for smaller scale uses.
Monday, January 28, 2008
"The modalities (of this arrangement) are being worked out which will be contingent on what exactly the participating countries would share and open up in lieu of having access to ISRO's data," said a senior home ministry official, adding that the in principle decision has been taken and would be ratified by the Union Cabinet in due course.
Experts from the SAARC countries were informed of this decision on Monday when they assembled here for a regional workshop on application of science and technology for disaster risk reduction management, inaugurated by Union home minister Shivraj Patil.
The official said since the satellite imaging of the region also involves the security concerns of the neighbouring countries, it would be discussed with each nation concerned. India has more than half a dozen operational remote sensing satellites in orbit covering the entire SAARC region.
The idea, as discussed in the workshop, is to use geo-informatics in risk-mapping, risk assessment and risk monitoring under diverse geographical, socio-economic and cultural settings. Indian experts specifically mentioned how remote sensing images taken even by commercial satellites clearly captured the tsunami along the eastern coast (2004), Kashmir earthquake (2005) and Bangladesh cyclone 'Sidr' (2007).
Experts felt that sharing of such data would not only help in assessing the actual damages/sufferings due to disasters but also help in improving transparency in relief and rehabilitation administration in the entire region.
During his inaugural address, the home minister also called upon the South Asian nations to use their strength in science and technology to build a robust system of prevention, mitigation and preparedness to reduce the risks of natural and man-made disasters.
Drawing attention of experts to the fact that various regions of the sub-continent are prone to earthquakes, Patil stressed the need for sustained scientific research on earthquake, particularly in the Himalayan region, so as to be able to identify the fault zones and the return period more accurately.
While discussing the issue, Indian experts later informed the participants about the possibility of using IIT, Roorkee, as a nucleus to form a thematic network in the region with a nodal agency in each SAARC country for sharing of information to deal with earthquakes.
The region comprises approximately one tenth of the Earth's land surface and plays a significant role in the climate of the Earth. The continent is surrounded by the Southern Ocean – comprising parts of the Pacific, Atlantic and Indian - the largest and stormiest of the oceans. The Antarctic and Southern Ocean host a unique and fragile ecosystem characterized by unique fauna and flora.
Political: In a situation where the legal and administrative system is prone to delays and irregularities, the fastest way of getting results is to approach a politically influential person for a reference. Trips to the block or Mandal headquarters to meet revenue officials or even the district headquarters to meet MLAs or MPs are undertaken routinely by those wishing to resolve disputes over loans, propoor schemes or land matters.
Social: A sign of rising affluence is for families to cast the net wider when they are searching for a groom. Recent trends from Krishna district with the highest farm incomes show that a town or city based groom fetches a higher dowry in the marriage market than the son of a large farmer of similar income. This is a clear indicator of how villagers perceive future prospects in rural and urban livelihoods.
The National Highway constitutes less than 2 percent of the total road network but carry a whopping 40 percent of the total road traffic. It is in this backdrop that the government has embarked on a programme to widen and strengthen them at a cost of over Rs. 185873 crores.
The Golden Quadrilateral project that envisages four-laning of 5846 km of roads connecting the four metros of the country has been completed to the extent of 87 percent. About 5079 km of roads have already been four laned.
The Delhi-Mumbai corridor, with a total length of 1419 km, has been fully completed. On the Mumbai-Chennai section 1145 km has been four laned out of the total length of 1290 kms. On the Chennai-Kolkata section 1462 km has been four-laned out of a total length of 1684 kms. On the Kolkata-Delhi section 1071 Kms of roads have been four-laned out of a total of 1453 km.
Sunday, January 27, 2008
Coordinates: 26°51′N 80°55′E / 26.85, 80.91
Time zone IST (UTC+5:30)
Area 238,566 km² (92,111 sq mi)
Largest city Kanpur
• Density 186,755,000 (1st)
• 783/km² (2,028/sq mi)
Language(s) Hindi, Urdu
Governor T. V. Rajeswar
Chief Minister Mayawati
Legislature (seats) Bicameral (404 + 108)
ISO abbreviation IN-UP
Uttar Pradesh Portal: Uttar Pradesh
1 The decision to possibly create an additional six districts is pending.
2As North-Western Provinces in 1835,
Renamed to United Provinces of Agra and Oudh in 1902,
Renamed to Uttar Pradesh in 1947
Seal of Uttar Pradesh
Seal of Uttar Pradesh
Uttar Pradesh (Hindi: उत्तर प्रदेश, Urdu: اتر پردیش, pronounced [ʊt̪ːər prəd̪eːʃ] , translation: Northern Province), [often referred to as U.P.], located in central-south Asia and northern India, is the most populous and fifth largest state in the Republic of India. With a population exceeding that of France, Germany, and the Netherlands combined, it is the most populous sub-national division in the world. U.P. is also possibly the state with the largest number of million-plus cities (at least eight).
Uttar Pradesh covers a large part of the highly fertile and densely populated upper Gangetic plain. It shares an international border with Nepal and is bounded by the Indian states of Uttarakhand, Himachal Pradesh, Haryana, Delhi, Rajasthan, Madhya Pradesh, Chhattisgarh, Jharkhand and Bihar. The administrative and legislative capital of Uttar Pradesh is Lucknow, and the financial and industrial capital is Kanpur. The state is also home to the tourism capital of India, Agra. The state's high court is based at Allahabad. Other notable cities in Uttar Pradesh include Aligarh, Azamgarh, Bareilly, Faizabad, Ghaziabad, Gorakhpur, Jhansi, Lakhimpur Kheri, Mathura, Meerut, Moradabad, Muzaffarnagar, NOIDA (New Okhla Industrial Development Authority), Saharanpur and Varanasi (Banaras).
Uttar Pradesh (UP) is the most populous state in India, even after losing Uttarkhand, with an estimated population of 186.7 million as of 2007 and a land area of 238,566 km². One-sixth of the world’s population lives in India and one-sixth of India’s population lives in UP. Only five countries of the world, China, the United States, Indonesia, Brazil and India itself have populations larger than that of UP, and UP and Uttarkhand have more than Brazil. The population density of the state at 783 persons per km². is the fourth highest among major states in the country. The Indo-Gangetic plain spans most of the state, has been the seat of ancient Hindu culture, religion and learning and has always played a prominent role in Indian political and cultural movements.Hindus as religious group form about 81% of state population.At the beginning of the 20th century, the population of UP was only 49 million and increased very slowly until 1951 (0.52 percent per annum) to reach 63 million. This was the period marked by high birth and death rates. The population increased rapidly in the next five decades due to a faster decline in the death rate compared to the birth rate. The population of the state increased from 63 million in 1951 to about 170 million in 2000, an addition of 117 million in the last five decades compared to an addition of only 15 million in the previous five decades. The population of the state is increasing at 2.19 percent per year (SRS, 1998). This implies that the state at present is adding a population of 3.8 million every year and more than 11 million every three years.
Conversion of real world Geographical variation into discrete objects is done through data models. It represents the linkage between the real world domain of geographical data and computer representation of these features. Data models discussed here are for representing the spatial information.
Data models are of two types: Raster and Vector.
In raster type of representation of geographical data, a set of cells located by coordinate is used; each cell is independently addressed with the value of an attribute. Each cell contains a single value and every location corresponds to a cell. One set of cell and associated value is a layer. Raster models are simple with which spatial analysis is easier and faster. Raster data models require a huge volume of data to be stored, fitness of data be limited by cell size & output is less beautiful.
Vector data model uses line segments or points represented by their explicit x, y coordinates to identify locations. Discrete objects are formed by connecting line segments which area is defined by set of line segments. Vector data models require less storage space, outputs are appreciable, estimation of area/perimeter and editing is faster and convenient. Spatial analysis is difficult with respect to writing the software programme.
Friday, January 25, 2008
The proliferation of GIS is explained by its unique ability to assimilate data from widely divergent sources, to analyse trends over time, and to spatially evaluate impacts caused by development.
For an experienced analyst, GIS is an extension one's own analytical thinking. The system has no in-built solutions for any spatial problems; it depends upon the analyst.
The importance of different factors of GIS in decreasing order is as under:
* Spatial Analysis
GIS involves complete understanding about patterns, space, and processes or methodology needed to approach a problem. It is a tool acting as a means to attain certain objective quickly and efficiently. Its applicability is realized when the user fully understands the overall spatial concept under which a particular GIS is established and analyses his specific application in the light of those established parameters.
Before the GIS implementation is considered the objectives, both immediate and long term, have to be considered. Since the effectiveness and efficiency (i.e. benefit against cost) of the GIS will depend largely on the quality of initial field data captured, organizational design has to be decided upon to maintain this data continuously. This initial data capture is most important.
According to the biogenic theory, petroleum is formed from the preserved remains of prehistoric zooplankton and algae which have been settled to the sea (or lake) bottom in large quantities under anoxic conditions. Over geological time this organic matter, mixed with mud, is buried under heavy layers of sediment. The resulting high levels of heat and pressure cause the organic matter to chemically change during diagenesis, first into a waxy material known as kerogen which is found in various oil shales around the world, and then with more heat into liquid and gaseous hydrocarbons in a process known as catagenesis.
Terrestrial plants, on the other hand, tend to form coal. Many of the coal fields date to the carboniferous period.
* 1 liter of regular gasoline is the time rendered result of about 23.5 metric tonnes of ancient phytoplankton material deposited on the ocean floor .
* The total fossil fuel used in the year 1997 is the result of 422 years of all plant matter that grew on the entire surface and in all the oceans of the ancient earth.
Fossil fuels are of great importance because they can be burned (oxidized to carbon dioxide and water), producing significant amounts of energy. The use of coal as a fuel predates recorded history. Semisolid hydrocarbons from seeps were also burned in ancient times, but these materials were mostly used for waterproofing and embalming.  Commercial exploitation of petroleum, largely as a replacement for oils from animal sources (notably whale oil) for use in oil lamps began in the nineteenth century. Natural gas, once flared-off as an un-needed byproduct of petroleum production, is now considered a very valuable resource. Heavy crude oil, which is very much more viscous than conventional crude oil, and tar sands, where bitumen is found mixed with sand and clay, are becoming more important as sources of fossil fuel. Oil shale and similar materials are sedimentary rocks containing kerogen, a complex mixture of high-molecular weight organic compounds which yields synthetic crude oil when heated (pyrolyzed), have not yet been exploited commercially.
Prior to the latter half of the eighteenth century windmills or watermills provided the energy needed for industry such as milling flour, sawing wood or pumping water, and burning wood or peat provided domestic heat. The wide-scale use of fossil fuels, coal at first and petroleum later, to fire steam engines enabled the Industrial Revolution. At the same time gas lights using natural gas or coal gas were coming into wide use. The invention of the internal combustion engine and its use in automobiles and trucks greatly increased the demand for gasoline and diesel oil, both made from fossil fuels. Other forms of transportation, railways and aircraft also required fossil fuels. The other major use for fossil fuels is in generating electricity.
Fossil fuels are also the main source of raw materials for the petrochemical industry.
Limits and alternatives
Global fossil carbon emission by fuel type, 1800-2000 AD.
Global fossil carbon emission by fuel type, 1800-2000 AD.
The principle of supply and demand suggests that as hydrocarbon supplies diminish, prices will rise. Therefore higher prices will lead to increased alternative, renewable energy supplies as previously uneconomic sources become sufficiently economical to exploit. Artificial gasolines and other renewable energy sources currently require more expensive production and processing technologies than conventional petroleum reserves, but may become economically viable in the near future. See Future energy development. Different alternative sources of energy include alcohols, hydrogen, nuclear, hydroelectric, solar, wind, and geothermal.
Levels of primary energy sources are the reserves in the ground. Flows are production. The most important part of primary energy sources are the carbon based fossil energy sources. Oil, coal, and gas stood for 79.6% of primary energy production during 2002 (in million tonnes of oil equivalent ) (34.9+23.5+21.2).
Levels (reserves) (EIA oil, gas, coal estimates, EIA oil, gas estimates)
* Oil: 1,050,691 to 1,277,702 billion barrels (167 to 203 km³) 2003-2005
* Gas: 6,040,208 - 6,805,830 billion cubic feet (171,040 to 192,720 km³) 6,805.830*0.182= 1,239 BBOE 2003-2005
* Coal: 1,081,279 million short tons (1,081,279*0.907186*4.879= 4,786 BBOE) (2004)
Flows (daily production) during 2002 (7.9 is a ratio to convert tonnes of oil equivalent to barrels of oil equivalent)
* Oil: (10,230*0.349)*7.9/365= 77 MBD
* Gas: (10,230*0.212)*7.9/365= 47 MBOED
* Coal: (10,230*0.235)*7.9/365= 52 MBOED
Years of production left in the ground with the most optimistic reserve estimates (Oil & Gas Journal, World Oil)
* Oil: 1,277,702/77/365= 45 years
* Gas: 1,239,000/47/365= 72 years
* Coal: 4,786,000/52/365= 252 years
Note that this calculation assumes that the product could be produced at a constant level for that number of years and that all of the reserves could be recovered. In reality, consumption of all three resources has been increasing. While this suggests that the resource will be used up more quickly, in reality, the production curve is much more akin to a bell curve. At some point in time, the production of each resource within an area, country, or globally will reach a maximum value, after which, the production will decline until it reaches a point where is no longer economically feasible or physically possible to produce. See Hubbert peak theory for detail on this decline curve with regard to petroleum.
The above discussion emphasizes worldwide energy balance. It is also valuable to understand the ratio of reserves to annual consumption (R/C) by region or country. For example, energy policy of the United Kingdom recognizes that Europe's R/C value is 3.0, very low by world standards, and exposes that region to energy vulnerability. Specific alternatives to fossil fuels are a subject of intense debate worldwide.
In the United States, more than 90% of greenhouse gas emissions come from the combustion of fossil fuels. Combustion of fossil fuels also produces other air pollutants, such as nitrogen oxides, sulphur dioxide, volatile organic compounds and heavy metals.
According to Environment Canada:
"The electricity sector is unique among industrial sectors in its very large contribution to emissions associated with nearly all air issues. Electricity generation produces a large share of Canadian nitrogen oxides and sulphur dioxide emissions, which contribute to smog and acid rain and the formation of fine particulate matter. It is the largest uncontrolled industrial source of mercury emissions in Canada. Fossil fuel-fired electric power plants also emit carbon dioxide, which may contribute to climate change. In addition, the sector has significant impacts on water and habitat and species. In particular, hydro dams and transmission lines have significant effects on water and biodiversity."
Combustion of fossil fuels generates sulphuric, carbonic, and nitric acids, which fall to Earth as acid rain, impacting both natural areas and the built environment. Monuments and sculptures made from marble and limestone are particularly vulnerable, as the acids dissolve calcium carbonate.
Fossil fuels also contain radioactive materials, mainly uranium and thorium, that are released into the atmosphere. In 2000, about 12,000 metric tons of thorium and 5,000 metric tons of uranium were released worldwide from burning coal. It is estimated that during 1982, US coal burning released 155 times as much radioactivity into the atmosphere as the Three Mile Island incident.
Burning coal also generates large amounts of bottom ash and fly ash. These materials are used in a wide variety of applications, utilizing, for example, about 40% of the US production.
Harvesting, processing, and distributing fossil fuels can also create environmental problems. Coal mining methods, particularly mountaintop removal and strip mining, have extremely negative environmental impacts, and offshore oil drilling poses a hazard to aquatic organisms. Oil refineries also have negative environmental impacts, including air and water pollution. Transportation of coal requires the use of diesel-powered locomotives, while crude oil is typically transported by tanker ships, each of which requires the combustion of additional fossil fuels.
Environmental regulation uses a variety of approaches to limit these emissions, such as command-and-control (which mandates the amount of pollution or the technology used), economic incentives, or voluntary programs.
An example of such regulation in the USA is the "EPA is implementing policies to reduce airborne mercury emissions. Under regulations issued in 2005, coal-fired power plants will need to reduce their emissions by 70 percent by 2018.".
In economic terms, pollution from fossil fuels is regarded as a negative externality. Taxation is considered one way to make societal costs explicit, in order to 'internalize' the cost of pollution. This aims to make fossil fuels more expensive, thereby reducing their use and the amount of pollution associated with them, along with raising the funds necessary to counteract these factors. Although European nations impose some pollution taxes, they also give billions of subsidies to the fossil fuel industry, offsetting the taxes.
They range from very volatile materials with low carbon:hydrogen ratios like methane, to liquid petroleum to nonvolatile materials composed of almost pure carbon, like anthracite coal. Methane can be found in hydrocarbon fields, alone, associated with oil, or in the form of methane clathrates. It is generally accepted that they formed from the fossilized remains of dead plants and animals by exposure to heat and pressure in the Earth's crust over hundreds of millions of years. This is known as the biogenic theory and was first introduced by Mikhail Lomonosov in 1757. There is an opposing theory that the more volatile hydrocarbons, especially natural gas, are formed by abiogenic processes, that is no living material was involved in their formation.
It was estimated by the Energy Information Administration that in 2005 86% of primary energy production in the world came from burning fossil fuels. With the remaining Non-fossil being hydro 6.3%, nuclear 6.0%, and other (geothermal, solar, wind, and wood and waste) 0.9 percent
Fossil fuels are non-renewable resources because they take millions of years to form and reserves are being depleted much faster than new ones are being formed. Concern about fossil fuel supplies is one of the causes of regional and global conflicts. The production and use of fossil fuels raise environmental concerns. A global movement toward the generation of renewable energy is therefore under way to help meet increased energy needs.
The burning of fossil fuels produces around 6.3 billion metric tons (= 6.3 gigatons) of carbon dioxide per year, but it is estimated that natural processes can only absorb about half of that amount so there is a net increase of 3.2 billion tons of atmospheric carbon dioxide per year. Carbon dioxide is one of the greenhouse gases that enhances radiative forcing and contributes to global warming causing the average surface temperature of the Earth to rise in response which climate scientists agree will cause major adverse effects, including on biodiversity and, over time, cause sea level rise.
NDVI is the acronym for normalized difference vegetation index. It is a simple formula using two satellite channels. If one band is in the visible region (VIS, for example AVHRR band 1) and one is in the near infrared (NIR, for example AVHRR band 2), then the NDVI is (NIR - VIS)/(NIR + VIS).
The reason NDVI is related to vegetation is that healthy vegetation reflects very well in the near infrared part of the spectrum. Green leaves have a reflectance of 20 percent or less in the 0.5 to 0.7 micron range (green to red) and about 60 percent in the 0.7 to 1.3 micron range (near infra-red). The visible channel gives you some degree of atmospheric correction. The value is then normalized to the range -1<=NDVI<=1 to partially account for differences in illumination and surface slope.
How is it useful?
NDVI provides a crude estimate of vegetation health and a means of monitoring changes in vegetation over time. The possible range of values is between -1 and 1, but the typical range is between about -0.1 (NIR less than VIS for a not very green area) to 0.6 (for a very green area).
Thursday, January 24, 2008
Absorption centered at about 0.65 µm (visible red) is controlled by chlorophyll pigment in green-leaf chloroplasts that reside in the outer or Palisade leaf. Absorption occurs to a similar extent in the blue. With these colors thus removed from white light, the predominant but diminished reflectance of visible wavelengths is concentrated in the green. Thus, most vegetation has a green-leafy color. There is also strong reflectance between 0.7 and 1.0 µm (near IR) in the spongy mesophyll cells located in the interior or back of a leaf, within which light reflects mainly at cell wall/air space interfaces, much of which emerges as strong reflection rays. The intensity of this reflectance is commonly greater (higher percentage) than from most inorganic materials, so vegetation appears bright in the near-IR wavelengths (which, fortunately, is beyond the response of mammalian eyes). These properties of vegetation account for their tonal signatures on multispectral images: darker tones in the blue and, especially red, bands, somewhat lighter in the green band, and notably light in the near-IR bands (maximum in Landsat's Multispectral Scanner Bands 6 and 7 and Thematic Mapper Band 4 and SPOT's Band 3).
Identifying vegetation in remote-sensing images depends on several plant characteristics. For instance, in general, deciduous leaves tend to be more reflective than evergreen needles. Thus, in infrared color composites, the red colors associated with those bands in the 0.7 - 1.1 µm interval are normally richer in hue and brighter from tree leaves than from pine needles.
These spectral variations facilitate fairly precise detecting, identifying and monitoring of vegetation on land surfaces and, in some instances, within the oceans and other water bodies. Thus, we can continually assess changes in forests, grasslands and range, shrublands, crops and orchards, and marine plankton, often at quantitative levels. Because vegetation is the dominant component in most ecosystems, we can use remote sensing from air and space to routinely gather valuable information helpful in characterizing and managing of these organic systems.
The ability to distinguish different types of vegetation was brought home to the writer (NMS) through a simple study using a densitometer to examine multispectral images of a strip of agricultural land near the Choptank River in the eastern shore of Maryland. These images were part of an experiment by my "boss", Dr. Warren Hovis, at Goddard. He had built a multispectral sensor to fly on an aircraft that would simulate images made by the same four bands on the ERTS-1 (Landsat-1) Multispectral Scanner (MSS).
The relative gray levels are plotted as a four band histogram for each of the numbered features in the above image. It should be evident that there are real differences in these band signatures among the vegetation and other features present; thus Mixed Hardwoods have different relative "brightness" patterns from Soybeans, from Old Hay, etc..
This discrimination capability implies that one of the most successful applications of multispectral space imagery is monitoring the state of the world's agricultural production. This application includes identifying and differentiating most of the major crop types: wheat, barley, millet, oats, corn, soybeans, rice, and others.
Remote sensing has proven a powerful "tool" for assessing the identity, characteristics, and growth potential of most kinds of vegetative matter at several levels (from biomes to individual plants). Vegetation behavior depends on the nature of the vegetation itself, its interactions with solar radiation and other climate factors, and the availability of chemical nutrients and water within the host medium (usually soil, or water in marine environments). A common measure of the status of a given plant, such as a crop used for human consumption, is its potential productivity (one such parameter has units of bushels/acre or tons/hectare, or similar units). Productivity is sensitive to amounts of incoming solar radiation and precipitation (both influence the regional climate), soil chemistry, water retention factors, and plant type. Examine the diagram below to see how these interact, keeping in mind that various remote sensing systems (e.g., meteorological or earth-observing satellites) can provide inputs to productivity estimation:
Developed by the United States Department of Defense, GPS is officially named NAVSTAR GPS (Contrary to popular belief, NAVSTAR is not an acronym, but simply a name given by Mr. John Walsh, a key decision maker when it came to the budget for the GPS program). The satellite constellation is managed by the United States Air Force 50th Space Wing. The cost of maintaining the system is approximately US$750 million per year, including the replacement of ageing satellites, and research and development.
Following the shootdown of Korean Air Lines Flight 007 in 1983, President Ronald Reagan issued a directive making the system available for free for civilian use as a common good. Since then, GPS has become a widely used aid to navigation worldwide, and a useful tool for map-making, land surveying, commerce, and scientific uses. GPS also provides a precise time reference used in many applications including scientific study of earthquakes, and synchronization of telecommunications networks.
Colors in color film are produced by stacking multiple layers of emulsions containing light-sensitive compounds (organic dyes) that filter out different wavelengths. In subtractive color film, the dye colors are: cyan, magenta, and yellow. Using the primary colors as reference, yellow subtracts blue, magenta subtracts green, and cyan subtracts red. So, when multicolored light enters a sensor, light from blue areas in the target or source, on striking the color film will bleach out parts of the yellow emulsion. The same pattern holds for green and red light, affecting the magenta and cyan layers, respectively. Then when white light passes through the multiple layers of the resulting transparencies (e.g., 35 mm slides), the now clear yellow areas will appear blue because the remaining cyan and magenta (so colored over these same areas) will filter out (subtract) red and green, leaving blue to display. The same reasoning holds for the other two primaries (red and green).
In color negative film from which color prints are made, the layer sensitive to red produces its complement color in the negative, which when printed onto paper produces red by leaving behind magenta and yellow dyes (from the [subtractive] color system). We won't elaborate further on the printing rationale; suffice to say that the red in print represents red from the source, green represents green, and blue represents blue.
80 to 1,200 miles - Asynchronous Orbits
Observation satellites, typically orbiting at altitudes from 300 to 600 miles (480 to 970 km), are used for tasks like photography. Observation satellites such as the Landsat 7 perform tasks such as:
* Ice and sand movement
* Locating environmental situations (such as disappearing rainforests)
* Locating mineral deposits
* Finding crop problems
Search-and-rescue satellites act as relay stations to rebroadcast emergency radio-beacon signals from a downed aircraft or ship in trouble.
The Space Shuttle is the familiar manned satellite, usually with a fixed duration and number of orbits. Manned missions often have the task of repairing existing expensive satellites or building future space stations.
Teledesic, with the financial backing of Bill Gates, promises broadband (high-speed) communications using many planned low Earth orbiting (LEO) satellites.
3,000 to 6,000 miles - Asynchronous Orbits
Science satellites are sometimes in altitudes of 3,000 to 6,000 miles (4,800 to 9,700 km). They send their research data to Earth via radio telemetry signals. Scientific satellite applications include:
* Researching plants and animals
* Earth science, such as monitoring volcanoes
* Tracking wildlife
* Astronomy, using the Infrared Astronomy Satellite
* Physics, by NASA's future study of microgravity and the current Ulysses Mission studying solar physics
6,000 to 12,000 miles - Asynchronous Orbits
For navigation, the U.S. Department of Defense built the Global Positioning System, or GPS. The GPS uses satellites at altitudes of 6,000 to 12,000 miles to determine the exact location of the receiver. The GPS receiver may be located:
* In a ship at sea
* In another spacecraft
* In an airplane
* In an automobile
* In your pocket
As consumer prices for GPS receivers come down, the familiar paper map may face tough competition. No more getting lost leaving the rental car agency at an unfamiliar airport!
* The U.S. military and the forces of allied nations used more than 9,000 GPS receivers during Operation Desert Storm.
* The National Oceanic and Atmospheric Administration (NOAA) used GPS to measure the exact height of the Washington Monument.
Advanced Communications Technology Satellite, launched in 1993, used multiple antennas for narrow-beam transmissions.
22,223 Miles - Geostationary Orbits
Weather forecasts visually bombard us each day with images from weather satellites, typically 22,223 miles over the equator. You can directly receive many of the actual satellite images using radio receivers and special personal-computer software. Many countries use weather satellites for their weather forecasting and storm observations.
Data, television, image and some telephone transmissions are routinely received and rebroadcast by communications satellites. Typical satellite telephone links have 550 to 650 milliseconds of round-trip delay that contribute to consumer dissatisfaction with this type of long-distance carrier. It takes the voice communications that long to travel all the way up to the satellite and back to Earth. The round-trip delay forces many to use telephone conversations via satellite only when no other links exist. Currently, voice over the Internet is experiencing a similar delay problem, but in this case due to digital compression and bandwidth limitations rather than distance.
Communications satellites are essentially radio relay stations in space. Satellite dishes get smaller as satellites get more powerful transmitters with focused radio "footprints" and gain-type antennas. Subcarriers on these same satellites carry:
* Press agency news feeds
* Stock market, business and other financial information
* International radio broadcasters moving from short-wave to (or supplementing their short-wave broadcasts with) satellite feeds using microwave uplink feeds
* Global television, such as CNN and the BBC
* Digital radio for CD-quality audio
see pictures and more
* Geostationary orbits (also called geosynchronous or synchronous) are orbits in which the satellite is always positioned over the same spot on Earth. Many geostationary satellites are above a band along the equator, with an altitude of about 22,223 miles, or about a tenth of the distance to the Moon. The "satellite parking strip" area over the equator is becoming congested with several hundred television, weather and communication satellites! This congestion means each satellite must be precisely positioned to prevent its signals from interfering with an adjacent satellite's signals. Television, communications and weather satellites all use geostationary orbits. Geostationary orbits are why a DSS satellite TV dish is typically bolted in a fixed position.
* The scheduled Space Shuttles use a much lower, asynchronous orbit, which means they pass overhead at different times of the day. Other satellites in asynchronous orbits average about 400 miles (644 km) in altitude.
* In a polar orbit, the satellite generally flies at a low altitude and passes over the planet's poles on each revolution. The polar orbit remains fixed in space as Earth rotates inside the orbit. As a result, much of Earth passes under a satellite in a polar orbit. Because polar orbits achieve excellent coverage of the planet, they are often used for satellites that do mapping and photography.
* Weather satellites help meteorologists predict the weather or see what's happening at the moment. Typical weather satellites include the TIROS, COSMOS and GOES satellites. The satellites generally contain cameras that can return photos of Earth's weather, either from fixed geostationary positions or from polar orbits.
* Communications satellites allow telephone and data conversations to be relayed through the satellite. Typical communications satellites include Telstar and Intelsat. The most important feature of a communications satellite is the transponder -- a radio that receives a conversation at one frequency and then amplifies it and retransmits it back to Earth on another frequency. A satellite normally contains hundreds or thousands of transponders. Communications satellites are usually geosynchronous.
* Broadcast satellites broadcast television signals from one point to another (similar to communications satellites).
* Scientific satellites perform a variety of scientific missions. The Hubble Space Telescope is the most famous scientific satellite, but there are many others looking at everything from sun spots to gamma rays.
* Navigational satellites help ships and planes navigate. The most famous are the GPS NAVSTAR satellites.
* Rescue satellites respond to radio distress signals (read this page for details).
* Earth observation satellites observe the planet for changes in everything from temperature to forestation to ice-sheet coverage. The most famous are the LANDSAT series.
* Military satellites are up there, but much of the actual application information remains secret. Intelligence-gathering possibilities using high-tech electronic and sophisticated photographic-equipment reconnaissance are endless. Applications may include:
o Relaying encrypted communications
o Nuclear monitoring
o Observing enemy movements
o Early warning of missile launches
o Eavesdropping on terrestrial radio links
o Radar imaging
o Photography (using what are essentially large telescopes that take pictures of militarily interesting areas)
Despite the significant differences between all of these satellites, they have several things in common. For example:
* All of them have a metal or composite frame and body, usually known as the bus. The bus holds everything together in space and provides enough strength to survive the launch.
* All of them have a source of power (usually solar cells) and batteries for storage.
Arrays of solar cells provide power to charge rechargeable batteries. Newer designs include the use of fuel cells. Power on most satellites is precious and very limited. Nuclear power has been used on space probes to other planets (read this page for details). Power systems are constantly monitored, and data on power and all other onboard systems is sent to Earth stations in the form of telemetry signals.
* All of them have an onboard computer to control and monitor the different systems.
* All of them have a radio system and antenna. At the very least, most satellites have a radio transmitter/receiver so that the ground-control crew can request status information from the satellite and monitor its health. Many satellites can be controlled in various ways from the ground to do anything from change the orbit to reprogram the computer system.
* All of them have an attitude control system. The ACS keeps the satellite pointed in the right direction.
The Hubble Space Telescope has a very elaborate control system so that the telescope can point at the same position in space for hours or days at a time (despite the fact that the telescope travels at 17,000 mph/27,359 kph!). The system contains gyroscopes, accelerometers, a reaction wheel stabilization system, thrusters and a set of sensors that watch guide stars to determine position.
With the Space Shuttle, an extremely important factor in choosing the launch window is the need to bring down the astronauts safely if something goes wrong. The astronauts must be able to reach a safe landing area where rescue personnel can be standing by. For other types of flights, including interplanetary exploration, the launch window must permit the flight to take the most efficient course to its very distant destination. If weather is bad or a malfunction occurs during a launch window, the flight must be postponed until the next launch window appropriate for the flight. If a satellite were launched at the wrong time of the day in perfect weather, the satellite could end up in an orbit that would not pass over any of its intended users. Timing is everything!
Earth's escape velocity is much greater than what's required to place an Earth satellite in orbit. With satellites, the object is not to escape Earth's gravity, but to balance it. Orbital velocity is the velocity needed to achieve balance between gravity's pull on the satellite and the inertia of the satellite's motion -- the satellite's tendency to keep going. This is approximately 17,000 mph (27,359 kph) at an altitude of 150 miles (242 km). Without gravity, the satellite's inertia would carry it off into space. Even with gravity, if the intended satellite goes too fast, it will eventually fly away. On the other hand, if the satellite goes too slowly, gravity will pull it back to Earth. At the correct orbital velocity, gravity exactly balances the satellite's inertia, pulling down toward Earth's center just enough to keep the path of the satellite curving like Earth's curved surface, rather than flying off in a straight line.
The orbital velocity of the satellite depends on its altitude above Earth. The nearer Earth, the faster the required orbital velocity. At an altitude of 124 miles (200 kilometers), the required orbital velocity is just over 17,000 mph (about 27,400 kph). To maintain an orbit that is 22,223 miles (35,786 km) above Earth, the satellite must orbit at a speed of about 7,000 mph (11,300 kph). That orbital speed and distance permits the satellite to make one revolution in 24 hours. Since Earth also rotates once in 24 hours, a satellite at 22,223 miles altitude stays in a fixed position relative to a point on Earth's surface. Because the satellite stays right over the same spot all the time, this kind of orbit is called "geostationary." Geostationary orbits are ideal for weather satellites and communications satellites.
The moon has an altitude of about 240,000 miles (384,400 km), a velocity of about 2,300 mph (3,700 kph) and its orbit takes 27.322 days. (Note that the moon's orbital velocity is slower because it is farther from Earth than artificial satellites.)
* To get a better feel for orbital velocities at different altitudes, check out NASA's orbital velocity calculator.
* To learn more about orbits and other topics in space flight, check out JPL's Basics of Space Flight Learners' Workbook.
* A detailed technical treatment of orbital mechanics can be found at this site.
In general, the higher the orbit, the longer the satellite can stay in orbit. At lower altitudes, a satellite runs into traces of Earth's atmosphere, which creates drag. The drag causes the orbit to decay until the satellite falls back into the atmosphere and burns up. At higher altitudes, where the vacuum of space is nearly complete, there is almost no drag and a satellite can stay in orbit for centuries (take the moon as an example).
Satellites usually start out in an orbit that is elliptical. The ground control station controls small onboard rocket motors to provide correction. The goal is to get the orbit as circular as possible. By firing a rocket when the orbit is at the apogee of its orbit (its most distant point from Earth), and applying thrust in the direction of the flight path, the perigee (lowest point from Earth) moves further out. The result is a more circular orbit
The satellite, manufactured by Israel Aerospace Industries (IAI), was sent into orbit from the Sriharikota Launching Range in India using an Indian rocket. It uses radar to identify targets under adverse weather conditions including dense clouds. As such, it differs from Israel's other reconnaissance satellites, the Ofek series, which rely on cameras. Advertisement
"This satellite joins a long list of satellites developed and launched by IAI," Yitzhak Nitzan, head of IAI, said. "To date we have launched 11 EROS, Ofek and Amos satellites, seven of which are in orbit."
IAI officials said that the satellite, which weighs some 300 kilograms, was launched at 5:45 A.M. Israel time, and was successfully placed in orbit. IAI ground stations reported receiving signals at 7:10 A.M. showing that all measuring parameters were operating correctly. But confirmation that all its systems are functioning properly is expected in 13 days, when permanent communications are established with a base in Israel. Officials in the security establishment said the long waiting period stemmed from the sophistication of the satellite's systems that could spot an object the size of a license plate or "even smaller."
Last May, Israel launched its Ofek 7 satellite at the Palmachim base in central Israel. It was also designed by IAI and was carried into orbit by the Israeli "Shavit" rocket.
The TECSAR launch was postponed a number of times in the past, largely due to bad weather conditions during the local monsoon period. The rocket used in the launch was the 15-story Indian-made PLSV that weighs 295 tons. It can carry a payload into orbit between 500 to 36,000 kilometers from earth. During its launch, the rocket sheds its tanks and interstage ring at a distance of 110 kilometers from earth to reduce its weight and escape the gravitational pull.
The Ofek 5 was launched in May, 2002, and the Ofek 7, last July, from the Palmachim missile range on Israel's coast. Israel intends to launch another two spy satellites as part of its strategic cooperation commitments, as well as seven other satellites for commercial use. IAI has recently revealed its advanced spy satellite, the OPTSAT 3000, and an upgraded version of the Amos model that will be able to provide commercial and military services.
Analysts say the launch further established Israel's place among the world's leading nations in satellite technology.
see more on http://www.haaretz.com
Wednesday, January 23, 2008
For most satellite launches, the scheduled launch rocket is aimed straight up at first. This gets the rocket through the thickest part of the atmosphere most quickly and best minimizes fuel consumption.
After a rocket launches straight up, the rocket control mechanism uses the inertial guidance system to calculate necessary adjustments to the rocket's nozzles to tilt the rocket to the course described in the flight plan. In most cases, the flight plan calls for the rocket to head east because Earth rotates to the east, giving the launch vehicle a free boost. The strength of this boost depends on the rotational velocity of Earth at the launch location. The boost is greatest at the equator, where the distance around Earth is greatest and so rotation is fastest.
How big is the boost from an equatorial launch? To make a rough estimate, we can determine Earth's circumference by multiplying its diameter by pi (3.1416). The diameter of Earth is approximately 7,926 miles (12,753 km). Multiplying by pi yields a circumference of something like 24,900 miles (40,065 km). To travel around that circumference in 24 hours, a point on Earth's surface has to move at 1,038 mph (1,669 kph). A launch from Cape Canaveral, Florida, doesn't get as big a boost from Earth's rotational speed. The Kennedy Space Center's Launch Complex 39-A, one of its launch facilities, is located at 28 degrees 36 minutes 29.7014 seconds north latitude. The Earth's rotational speed there is about 894 mph (1,440 kph). The difference in Earth's surface speed between the equator and Kennedy Space Center, then, is about 144 mph (229 kph). (Note: The Earth is actually oblate -- fatter around the middle -- not a perfect sphere. For that reason, our estimate of Earth's circumference is a little small.)
Considering that rockets can go thousands of miles per hour, you may wonder why a difference of only 144 mph would even matter. The answer is that rockets, together with their fuel and their payloads, are very heavy. For example, the February 11, 2000 lift-off of the Space Shuttle Endeavor with the Shuttle Radar Topography Mission required launching a total weight of 4,520,415 pounds (2,050,447 kg). It takes a huge amount of energy to accelerate such a mass to 144 mph, and therefore a significant amount of fuel. Launching from the equator makes a real difference.
Once the rocket reaches extremely thin air, at about 120 miles (193 km) up, the rocket's navigational system fires small rockets, just enough to turn the launch vehicle into a horizontal position. The satellite is then released. At that point, rockets are fired again to ensure some separation between the launch vehicle and the satellite itself.
Inertial Guidance Systems
A rocket must be controlled very precisely to insert a satellite into the desired orbit. An inertial guidance system (IGS) inside the rocket makes this control possible. The IGS determines a rocket's exact location and orientation by precisely measuring all of the accelerations the rocket experiences, using gyroscopes and accelerometers. Mounted in gimbals, the gyroscopes' axes stay pointing in the same direction. This gyroscopically-stable platform contains accelerometers that measure changes in acceleration on three different axes. If it knows exactly where the rocket was at launch and it knows the accelerations the rocket experiences during flight, the IGS can calculate the rocket's position and orientation in space.
* The path a satellite follows is an orbit. In the orbit, the farthest point from Earth is the apogee, and the nearest point is the perigee.
* Artificial satellites generally are not mass-produced. Most satellites are custom built to perform their intended functions. Exceptions include the GPS satellites (with over 20 copies in orbit) and the Iridium satellites (with over 60 copies in orbit).
* Approximately 23,000 items of space junk -- objects large enough to track with radar that were inadvertently placed in orbit or have outlived their usefulness -- are floating above Earth. The actual number varies depending on which agency is counting. Payloads that go into the wrong orbit, satellites with run-down batteries, and leftover rocket boosters all contribute to the count. This online catalog of satellites has almost 26,000 entries!
Although anything that is in orbit around Earth is technically a satellite, the term "satellite" is typically used to describe a useful object placed in orbit purposely to perform some specific mission or task. We commonly hear about weather satellites, communication satellites and scientific satellites.
In May, 1946, Project RAND had released the Preliminary Design of an Experimental World-Circling Spaceship, which stated, "A satellite vehicle with appropriate instrumentation can be expected to be one of the most potent scientific tools of the Twentieth Century. The United States had been considering launching orbital satellites since 1945 under the Bureau of Aeronautics of the United States Navy. The United States Air Force's Project RAND eventually released the above report, but did not believe that the satellite was a potential military weapon; rather, they considered it to be a tool for science, politics, and propaganda. In 1954, the Secretary of Defense stated, "I know of no American satellite program."
On July 29, 1955, the White House announced that the U.S. intended to launch satellites by the spring of 1958. This became known as Project Vanguard. On July 31, the Soviets announced that they intended to launch a satellite by the fall of 1957.
Following pressure by the American Rocket Society, the National Science Foundation, and the International Geophysical Year, military interest picked up and in early 1955 the Air Force and Navy were working on Project Orbiter, which involved using a Jupiter C rocket to launch a satellite. The project succeeded, and Explorer 1 became the United States' first satellite on January 31, 1958.
The largest artificial satellite currently orbiting the Earth is the International Space Station.
Developable surface—A developable surface is a simple geometric form capable of being flattened without stretching. Map projections can be grouped by the developable surface they use: cylinder, cone, or plane.
Ellipsoid—A mathematical figure that approximates the shape of the Earth in form and size, and which is used as a reference surface for geodetic surveys. Used interchangeably with Spheriod.
Equal-area—A map projection where every part, as well as the whole, has the same area as the corresponding part on the Earth, at the same reduced scale.
Equator—The line which encircles the Earth at an equal distance from the North and South Poles.
Equidistant—A map projection that shows true distances from the center of the projection or along a special set of lines. For example, an Azimuthal Equidistant map centered at Washington, DC, shows the correct distance between Washington, DC, and any other point on the projection. It shows the correct distance between Washington, DC, and San Diego and between Washington, DC, and Seattle, but it does not show the correct distance between San Diego and Seattle.
Graticule—A network of lines representing a selection of the Earth's parallels and meridians.
Great circle—A circle formed on the surface of a sphere by a plane that passes through the center of the sphere. The Equator, each meridian, and each other full circumference of the Earth forms a great circle. The arc of a great circle shows the shortest distance between points on the surface of the Earth.
Grid—Two sets of parallel lines intersecting at right angles, forming a rectangular Cartesian coordinate system superimposed on a map projection. Sometimes the term "grid" is used loosely to mean the projection system itself rather than the rectangular system superimposed on the projection.
Latitude—Angular distance, in degrees, minutes, and seconds measured from the center of the Earth, of a point north or south of the Equator. Latitude may also be measured in decimal degrees.
Longitude—Angular distance, in degrees, minutes, and seconds measured from the center of the Earth, of a point east or west of the Prime Meridian. Longitude may also be measured in decimal degrees.
Meridian—A great circle on the surface of the Earth, passing through the geographical poles and some third point on the Earth's surface. All points on a given meridian have the same longitude.
Parallel—A circle or approximation of a circle on the surface of the Earth, parallel to the Equator and connecting points of equal latitude.
Planar—A map projection resulting from the conceptual projection of the Earth onto a tangent or secant plane. Usually, a planar projection is the same as an azimuthal projection.
Secant and tangent projections on a globe and map
Prime Meridian—The meridian of longitude 0 degrees, used as the origin for the measurement of longitude. The meridian of Greenwich, England, is the internationally accepted prime meridian in most cases.
Projection parameters—A series of values that define a particular projection, and that tell how the projection is related to the Earth. Projection parameters may indicate the point of tangency, or the lines where a secant surface intersects the Earth. They also define the spheriod used to create the projection, and any other information necessary to identify the projection.
Rhumb line—A rhumb line is a line on the surface of the Earth cutting all meridians at the same angle. A rhumb line shows true direction. Parallels and meridians, which also maintain constant true directions, may be considered special cases of the rhumb line. A rhumb line is a straight line on a Mercator projection. A straight rhumb line does not show the shortest distance between points unless the points are on the Equator or on the same meridian. A navigator can proceed between any two points along a rhumb line by maintaining a constant bearing, or compass direction.
Scale—The relationship between a distance on a map, chart, or photograph, and the corresponding distance on the Earth. Scale is usually given as a fraction or ratio: 1:2,000,000, or 1/2,000,000.
Secant—Cutting the sphere or spheroid along a line or lines. A secant cone or cylinder intersects the sphere or spheroid along two separate lines; these lines are parallels of latitude if the axes of the geometric figures coincide. A secant plane intersects the sphere or spheroid along a line that is a parallel of latitude if the plane is at right angles to the axis.
Spherical – Approximating the shape of a sphere.
Spheroid—A mathematical figure that approximates the shape of the Earth in form and size, and which is used as a reference surface for geodetic surveys. Used interchangeably with Ellipsoid.
Tangent—Touching at a single point or along a single line. A tangent cone or cylinder touches the sphere or spheroid along a single line. This line is a parallel of latitude if the axes of the geometric figures coincide.
Zenithal—A map projection in which the direction from a given central point to any other point is shown correctly. Also called an azimuthal projection.
Classification based on distortion characteristics
A projection that maintains accurate relative sizes is called an equal area, or equivalent projection. These projections are used for maps that show distributions or other phenomena where showing area accurately is important. Examples are the Lambert Azimuthal Equal-Area projection and the Albers Equal-Area Conic projection.
An Azimuthal Equal-Area projection The National Atlas of the United States uses a Lambert Azimuthal Equal-Area projection to display information in the online Map Maker. In addition to its equal-area properties, this projection also shows true directions from the center point of the map. This means that the projection works well for mapping areas that extend equally from the center point, such as North America.
Mercator projection on a globe and map. Mercator projection A projection that maintains angular relationships and accurate shapes over small areas is called a conformal projection. These projections are used where angular relationships are important, such as for navigational or meteorological charts. Examples are the Mercator projection and the Lambert Conformal Conic projection. The U.S. Geological Survey uses a conformal projection for many of its topographic maps.
A projection that maintains accurate distances from the center of the projection or along given lines is called an equidistant projection. These projections are used for radio and seismic mapping, and for navigation. Examples are the Equidistant Conic projection and the Equirectangular projection. The Azimuthal Equidistant projection is the projection used for the emblem of the United Nations.
A projection that maintains accurate directions (and therefore angular relationships) from a given central point is called an azimuthal or zenithal projection. These projections are used for aeronautical charts and other maps where directional relationships are important. Examples are the Gnomonic projection and the Lambert Azimuthal Equal-Area projection.
A map projection may combine several of these characteristics, or may be a compromise that distorts all the properties of shape, area, distance, and direction, within some acceptable limit. Examples of compromise projections are the Winkel Tripel projection and the Robinson projection, often used for world maps.
Classification based on developable surface
Map projections can also be classified based on the shape of the developable surface to which the Earth's surface is projected. A developable surface is a simple geometric form capable of being flattened without stretching, such as a cylinder, cone, or plane.Cylindrical projection showing tangent at a selected line and secant along two lines.
For example, a cylindrical projection projects information from the spherical Earth to a cylinder. The cylinder may be either tangent to the Earth along a selected line, or may be secant (intersect the Earth) along two lines. Imagine that once the Earth's surface is projected, the cylinder is unwrapped to form a flat surface. The lines where the cylinder is tangent or secant are the places with the least distortion.
Transverse and oblique mercator projections on a cylinder and map.A Mercator projection is created using a cylinder tangent at the equator. A Transverse Mercator projection is created using a cylinder that is tangent at a selected meridian. An Oblique Mercator projection is created using a cylinder that is tangent along a great circle other than the equator or a meridian.
Polyconic projection on a globe and map.
Polyconic projection A conic projection projects information from the spherical Earth to a cone that is either tangent to the Earth at a single parallel, or that is secant at two standard parallels. Once the projection is complete, the cone is unwrapped to form a flat surface. The lines where the cone is tangent or secant are the places with the least distortion. A polyconic projection uses a series of cones to reduce distortion.
A planar projection projects information to a plane. The plane may be either tangent or secant.
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Commonly Used Map Projection Terms
Azimuth—The angle, measured in degrees, between a base line radiating from a center point and another line radiating from the same point. Normally, the base line points North, and degrees are measured clockwise from the base line.
Azimuthal—A map projection in which the direction from a given central point to any other point is shown correctly. Also called a zenithal projection.
Aspect—The placement of a projection system relative to the Earth's axis. A polar aspect is tangent at the pole, an equatorial aspect is tangent at the Equator, and an oblique aspect is tangent anywhere else. (The word "aspect" has replaced the word "case" in the modern cartographic literature.)
Cartesian coordinate system —A coordinate system in which a point's location is described by its distances from a set of perpendicular lines that intersect at an origin, either two lines in a plane or three in space.
Conformal—A map projection in which the angles at each point are preserved. This means that the shapes of small areas are maintained accurately. The size of most areas, however, is distorted.
Conic—A map projection where the Earth's surface is projected onto a tangent or secant cone, which is then cut from apex to base and laid flat.
Conic Projection on a globe and map. One shows tangent at a single parallel and the other secant at two parallels.
Cylindrical—A map projection where the Earth's surface is projected onto a tangent or secant cylinder, which is then cut lengthwise and laid flat.
There are hundreds of different map projections. The process of transferring information from the Earth to a map causes every projection to distort at least one aspect of the real world – either shape, area, distance, or direction.
Each map projection has advantages and disadvantages; the appropriate projection for a map depends on the scale of the map, and on the purposes for which it will be used. For example, a projection may have unacceptable distortions if used to map the entire country, but may be an excellent choice for a large-scale (detailed) map of a county. The properties of a map projection may also influence some of the design features of the map. Some projections are good for small areas, some are good for mapping areas with a large east-west extent, and some are better for mapping areas with a large north-south extent.
Some projections have special properties. For example, a Mercator projection has straight rhumb lines and is therefore excellent for navigation, because compass courses are easy to determine.
Tuesday, January 22, 2008
Example of FSMS Trends
Given that several factors affect household food security, FSMS's need to incorporate different factors in order to have a complete picture of a particular situation. A FSMS typically provides information gathered regularly (e.g., quarterly) from households, community members or key informants, and market traders. The latter data are combined with other types of information such as crop forecasts, remote sensing and satelitte images, and producer and consumer prices in order to have micro (e.g., household or community) and macro (e.g., sub-national or national) perspectives.
First statements by Lambert (France) of principles underlying photogrammetry
First ever photographs by Daguerre and Nepce, in France
French used photos in making topographic maps.
Photographs important in documenting exploration of the U.S. West (through 1870's).
Maxwell proposed proof of trichromatic color vision by photographic experiments (1861; Sutton).
Pictures of Paris from cameras mounted in free and captive balloons.
Du Hauron analyzed multispectral imagery with single-lens beam splitter technique.
Claims of photos for military observations from balloons during American Civil War; none survive.
Simple additive color projection and viewing developed.
Camera airborne on kites in England, France, Russia.
First color separations produced.
Photos used by Seville in topographical surveys in Canada.
Ives invented three-lens multispectral camera.
Cameras attached to carrier pigeons.
Wilbur Wright took first photos (movies) from an airplane.
Berthon's lenticular color film process for additive system.
Orel-Zeiss Stereoautograph: precursor to serial stereo-photos.
Aerial photos used by British R.A.F. for reconnaissance, changing tactics of work in W.W.I.
Unites States Signal corps used aerial photos in Mexican border war.
Aerial photos used by petroleum geologists for exploration.
Multilayered color film developed.
First aerial spectrophotography of the Earth by Krinov and colleagues (Russia).
Extensive use of aerial photos in Earth sciences and agriculture.
Testing of aerial IR sensitive film from stratospheric balloon.
Kodachrome appeared on market.
Color film used in aerial surveys.
Bausch and Lomb multiplex photogrammetric plotter.
Kelsh plotters came into wide use.
Rapid advances in development of black-and-white and color IR (CIR) film for camouflage detection and haze penetration.
Eardley's Aerial Photos: Their Use and Interpretation published
Tremendous strides in aerial photography and photogrammetry resulting from W.W.II military needs.
1944 First edition of AS's Manual of Photogrammetry.
1944 Military studies of water-depth penetration by two-band aerial photography.
1947 Publication of Krinov's Spectral Reflectance Properties of Natural Materials.
1950's Orthophoto mapping became popular.
1952 Color aerial photos used in geological mapping.
1953 Colwell (U.S.) demonstrated detection of disease and stress in vegetation (published 1956).
1950's Term "Remote Sensing" first used (generally ascribed to Evelyn Pruitt; see footnote on page Intro-1).
1956 Soviets published on spectro-zonal photography for mapping soils.
1960's Color film entered into common use in aerial photography.
1960 Colwell's Manual of Photointerpretation and Ray's Aerial Photographs in Geologic Interpretation and Mapping published.
1960's Considerable activity in multispectral photography applications.
1960 Wheeler's colorvision additive multispectral system.
1962 United States and Russian nine-lens multispectral cameras; Itek camera (ten lens) in 1963.
1963 USAF built Additive Color Viewer-Printer
1964 NASA inaugurated programs in testing usefulness of multiband photography for Earth resources.
1965 Multispectral additive color system developed by Yost and Wenderoth.
1967 First practical uses of UV photography.
1967 Two-volume Earth Resources Surveys from Space prepared by U.S. Army Corps of Engineers.
1968 ASP's Manual of Color Aerial Photography.
1968 SO65 multispectral photography experiment on Apollo-9
1975 Publication of ASP's Manual of Remote Sensing.
Having now covered some of the principles behind the nature and use of remote sensing data and methodologies, including sensors and image processing, we switch to a survey of the era of satellite remote sensing (and some mention of aircraft remote sensing and space photography by astronauts/cosmonauts) introduced from an historical framework. Special topics near the end will be multiplatform systems, military surveillance, and remote sensing as it applies to medical imaging systems.
Remote sensing as a technology started with the first photographs in the early nineteenth century (see first page of Overview). To learn about the milestones in remote sensing prior to the first Landsat, look to these three areas - Photographic Methods, Non-Photographic Sensor Systems, Space Imaging Systems on the next 3 pages. That review (extracted from the writer's Landsat Tutorial Workbook) ends with events in 1979. You can also find more on the general history of U.S. and foreign space programs in Appendix A and at this online Web site: review-3. NASA's Earth Sciences Enterprise program has prepared a brief but informative summary of its first 40 years of Earth Observations, accessed at its site.
We present major highlights subsequent to 1979 both within this Introduction and throughout the Tutorial. Some of these highlights include short summaries of major space-based programs such as launching several other satellite/sensor systems similar to Landsat; inserting radar systems into space; proliferating weather satellites; orbiting a series of specialized satellites to monitor the environment using, among others, thermal and passive microwave sensors; developing sophisticated hyperspectral sensors; and deploying a variety of sensors to gather imagery and other data on the planets and astronomical bodies.
The launch of these civilian satellites will be preceded by the launch, in February, of Cartosat-2A, a satellite that will be used for defence purposes with sub-meter resolution. ISRO is building also building Cartosat-3, with a resolution of about 0.35m.
India and France are jointly working on two satellites, Saral and Megha Tropiques, to track climate changes in the ocean and the tropics. ISROis building a family of radar imaging satellites that carry synthetic aperture radars, all-weather imaging sensors that are capable of taking images in cloudy and snow-covered regions.
Monday, January 21, 2008
To be food secure means that:
* Food is available - The amount and quality of food available globally, nationally and locally can be affected temporarily or for long periods by many factors including climate, disasters, war, civil unrest, population size and growth, agricultural practices, environment, social status and trade.
* Food is affordable - When there is a shortage of food prices increase and while richer people will likely still be able to feed themselves, poorer people may have difficulty obtaining sufficient safe and nutritious food without assistance.
* Food is utilised - At the household level, sufficient and varied food needs to be prepared safely so that people can grow and develop normally, meet their energy needs and avoid disease.
The ruins of Mohenjo Daro and of Harappa (2300-1700 B.C.) are the most ancient testimonies of a methodic urbanism. Long before Miletus was rebuilt in 479 B.C. by Hippodamos of Milet, these ancient cities of India were laid out on a grid pattern formed by rectangular blocks and comfortable streets.The blocks were composed by a wide range of house types from small tenements to large houses with one or several courtyards. Sir Mortimer Wheeler mentions in his work 'Civilisation of the Indus and Beyond' the presence of elaborate sanitary installations, both public and private!
The astonishing wealth of public and sacred buildings and the sophisticated housing structures do necessarily suggest a high development of urban culture and highly articulate knowledge of planning and urbanistic methodologies. Infact Harappa and Mohenjo Daro are only the two major discovered cities of a large urban area counting no less than 100 cities!
In its long and dense history, the Eastern world has been guided and influenced by complex philosophical thinking addressing all aspects of life, from concepts of nature and of man, of the natural environment and of the built culture of cities and dwellings.
Architecture and urbanism were based on holistic design systems which reflected man's acivities within a coherent pattern of the universe, where the laws of nature would be the same laws than the ones governing the building of cities and dwellings.
Unfortunately new urbanizations have suffered from the demise of traditional values and have been influenced by Western modernism, instrumentalized as the cultural paradigm of globalization.
The faithless and valueless orientation of the imported modernist theories and urbanistic planning technologies have culturally uprooted settlement patterns and produced ecologically wasteful land use systems leading to a tremendous hardship for human habitat.
It would be of highest efficiency to re-visit indigenous vernacular models and patterns and resource the contemporary design strategies with the most respectful consideration of holistic design theories.
It seems an unpretentious claim under the modern circumstances to reassess the authority of traditional and local crafts, materials and methodologies to address in an efficiently wholesome way issues of dwelling, climate and resources, and particularly issues regarding the revalorization of social-cultural patterns supporting vital communities in the perspective of identity and continuity.
The world's oldest holistic design system 'vastu' predates and inspired 'feng shui', a now fashionable reference in Western architectural glossaries and still an influential design support in China....Important texts in the 'Mansara' and the 'Mayamata', known as 'vastu-shastras' corresponding to 'treatises on dwelling' deal with city planning and building design.
These texts set out standards that govern the design of cities. They include description of site analysis, dimensions and patterns of towns, location of temples and royal buildings, location of bazars, circulation routes and axial systems, etc.
These standards also cover environmental concerns, the variety of lifestyles and activities, and rule the bureaucratical procedures and regulating structures in the context of a legitimate administration of these laws.
"The name given to form is 'mandala'. Thus the so-called 'vastu-purusha' mandala is the form assumed by existence, by the phenomenal world.....the 'vastu-purusha' mandala is an image of the laws governing the cosmos, to which man are just as subject as is the earth on which they build.
In their activities as builders men order their environment in the same way as once in the past Brahma forced the undefined 'purusha' into a geometric form.....building is an act of bringing disordered existence into conformity with the basic laws that govern it.
This can only be achieved by making each monument, from the hermit's retreat to the layout of a city, follow exactly the magic diagram of the 'vastu-purusha' mandala."
"Living Architecture: Indian"
Lake Town in India
The Lake City Corporation Private Ltd. is in the process of purchasing over 7000 acres of land with the purpose of developing a "Hill Station" by the name of "Lake Town" on the banks of the Warasgaon dam backwater lake in the Pune district of Maharashtra state in India.
The development comprises a number of villages or towns among which the most important are: Dhamanhole in the West and Mugaon, Dasawe and Admal which are located inland.
The location is a strip of of about 20 km length and about 5 km width. One end of the strip is bordering the coastal area of Konkan. The project location is about 50 km from Pune city one the Pune Sinhagad-Panshet road.
About 4825 acres of land have already been aquired and the State Government has recently granted permission for developing the land into a "Hill Station".
The Hok Planning Group
(Hellmuth, Obata + Kassabaum)
The Lake Town development proposal is based on traditional patterns and types of Indian towns, urban fabric systems and buildings and referring to the traditional knowledge of old Indian treatises.
Types are used as organizational tools in the Master Plan and design standards help to bring the elements of typology into the appropriate relationship to the particular character of each village in Lake Town.
The proposed design standards acknowledge traditional patterns of Indian towns and buildings. They are comprised of systematic rules that incorporate and allow interpretations and variations respecting existing features of land and culture, as well as local characteristics and traditions.
The Design Standards proposed for the Lake Town development project serve to organize the layout and definition of the urban fabric by referring to following principles:
--Organization in terms of function, type, disposition and configuration, --They are prescriptive rather than restrictive, allowing for originality and creativity, as well as innovative adjustments between inherited traditions and new challenges and potentials,
--They encourage traditional and local construction techniques and materials, rather than imported ones, --They assume the premise of the human body as the scale factor, as traditional and vernacular and classical cultures have successfully practiced since the origin of human settlements,
--They encompass a convention or style or pattern language that is contextually dealing with traits, motives, crafts, practices, etc. which engage climate, topography, hydrology, natural resources, etc. in a sensitive and cultivated manner, --They encourage to communicate symbols and meanings based on social, cultural and religious patterns by means of style conventions identifying commonly shared beliefs and values .
The contribution on Indian Urbanism and the Lake Town Project has been spearheaded by the HOK Planning Group with Chip Crawford, Douglas A. Smith, Dhaval Barbhaya, Todd Meyer, David Carrico, and Oscar Machado. The HOK Planning Group has thouroughly engaged New Urbanism strategies in other projects in the USA and China to be published soon in KATARXIS!