Remote sensing

Remote sensing

Overview
Remote sensing is the acquisition of information about an object or phenomenon, without making physical contact with the object. In modern usage, the term generally refers to the use of aerial sensor technologies to detect and classify objects on Earth (both on the surface, and in the atmosphere
Atmosphere
An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...

 and oceans) by means of propagated signals
Wave propagation
Wave propagation is any of the ways in which waves travel.With respect to the direction of the oscillation relative to the propagation direction, we can distinguish between longitudinal wave and transverse waves....

 (e.g. electromagnetic radiation
Electromagnetic radiation
Electromagnetic radiation is a form of energy that exhibits wave-like behavior as it travels through space...

 emitted from aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...

 or satellites).

There are two main types of remote sensing: passive remote sensing and active remote sensing.
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Encyclopedia
Remote sensing is the acquisition of information about an object or phenomenon, without making physical contact with the object. In modern usage, the term generally refers to the use of aerial sensor technologies to detect and classify objects on Earth (both on the surface, and in the atmosphere
Atmosphere
An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...

 and oceans) by means of propagated signals
Wave propagation
Wave propagation is any of the ways in which waves travel.With respect to the direction of the oscillation relative to the propagation direction, we can distinguish between longitudinal wave and transverse waves....

 (e.g. electromagnetic radiation
Electromagnetic radiation
Electromagnetic radiation is a form of energy that exhibits wave-like behavior as it travels through space...

 emitted from aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...

 or satellites).

Overview


There are two main types of remote sensing: passive remote sensing and active remote sensing. Passive sensors detect natural radiation that is emitted or reflected by the object or surrounding area being observed. Reflected sunlight
Sunlight
Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon.When the direct solar radiation is not blocked...

 is the most common source of radiation measured by passive sensors. Examples of passive remote sensors include film photography
Photography
Photography is the art, science and practice of creating durable images by recording light or other electromagnetic radiation, either electronically by means of an image sensor or chemically by means of a light-sensitive material such as photographic film...

, infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...

, charge-coupled devices, and radiometers. Active collection, on the other hand, emits energy in order to scan objects and areas whereupon a sensor then detects and measures the radiation that is reflected or backscattered from the target. RADAR
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...

 and LiDAR
LIDAR
LIDAR is an optical remote sensing technology that can measure the distance to, or other properties of a target by illuminating the target with light, often using pulses from a laser...

 are examples of active remote sensing where the time delay between emission and return is measured, establishing the location, height, speed and direction of an object.

Remote sensing makes it possible to collect data on dangerous or inaccessible areas. Remote sensing applications include monitoring deforestation
Deforestation
Deforestation is the removal of a forest or stand of trees where the land is thereafter converted to a nonforest use. Examples of deforestation include conversion of forestland to farms, ranches, or urban use....

 in areas such as the Amazon Basin
Amazon Basin
The Amazon Basin is the part of South America drained by the Amazon River and its tributaries that drains an area of about , or roughly 40 percent of South America. The basin is located in the countries of Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, and Venezuela...

, glacial
Glacier
A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...

 features in Arctic and Antarctic regions, and depth sounding
Depth Sounding
Depth sounding refers to a historical nautical term for measuring depth; it is often referred to simply as sounding. Sounding is finding the depth of a given point in a body of water. Sounding data is used in bathymetry to make maps of the floor of a body of water. Soundings were traditionally...

 of coastal and ocean depths. Military collection during the Cold War
Cold War
The Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...

 made use of stand-off collection of data about dangerous border areas. Remote sensing also replaces costly and slow data collection on the ground, ensuring in the process that areas or objects are not disturbed.

Orbital platforms collect and transmit data from different parts of the electromagnetic spectrum
Electromagnetic spectrum
The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The "electromagnetic spectrum" of an object is the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object....

, which in conjunction with larger scale aerial or ground-based sensing and analysis, provides researchers with enough information to monitor trends such as El Niño and other natural long and short term phenomena. Other uses include different areas of the earth science
Earth science
Earth science is an all-embracing term for the sciences related to the planet Earth. It is arguably a special case in planetary science, the Earth being the only known life-bearing planet. There are both reductionist and holistic approaches to Earth sciences...

s such as natural resource management
Natural resource management
Natural resource management refers to the management of natural resources such as land, water, soil, plants and animals, with a particular focus on how management affects the quality of life for both present and future generations ....

, agricultural fields such as land usage and conservation, and national security and overhead, ground-based and stand-off collection on border areas.

By satellite, aircraft, spacecraft, buoy, ship, and helicopter images, data is created to analyze and compare things like vegetation rates, erosion, pollution, forestry, weather, and land use. These things can be mapped, imaged, tracked and observed. The process of remote sensing is also helpful for city planning, archaeological investigations, military observation and geomorphological surveying.

Data acquisition techniques


The basis for multispectral collection and analysis is that of examined areas or objects that reflect or emit radiation that stand out from surrounding areas.

Applications of remote sensing data

  • Conventional radar
    Radar
    Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...

     is mostly associated with aerial traffic control, early warning, and certain large scale meteorological data. Doppler radar is used by local law enforcements’ monitoring of speed limits and in enhanced meteorological collection such as wind speed and direction within weather systems. Other types of active collection includes plasmas
    Plasma (physics)
    In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...

     in the ionosphere
    Ionosphere
    The ionosphere is a part of the upper atmosphere, comprising portions of the mesosphere, thermosphere and exosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere...

    . Interferometric synthetic aperture radar
    Interferometric synthetic aperture radar
    Interferometric synthetic aperture radar, also abbreviated InSAR or IfSAR, is a radar technique used in geodesy and remote sensing. This geodetic method uses two or more synthetic aperture radar images to generate maps of surface deformation or digital elevation, using differences in the phase of...

     is used to produce precise digital elevation model
    Digital elevation model
    A digital elevation model is a digital model or 3-D representation of a terrain's surface — commonly for a planet , moon, or asteroid — created from terrain elevation data....

    s of large scale terrain (See RADARSAT
    RADARSAT
    The RADARSAT constellation is a pair of Canadian Remote Sensing satellites. The constellation consists of:* RADARSAT-1, launched 1995* RADARSAT-2, launched 2007-The Company:...

    , TerraSAR-X
    TerraSAR-X
    TerraSAR-X, a German Earth observation satellite, is a joint venture being carried out under a public-private-partnership between the German Aerospace Center DLR and EADS Astrium GmbH; the exclusive commercial exploitation rights are held by the geo-information service provider Infoterra GmbH....

    , Magellan
    Magellan probe
    The Magellan spacecraft, also referred to as the Venus Radar Mapper, was a 1,035-kilogram robotic space probe launched by NASA on May 4, 1989, to map the surface of Venus using Synthetic Aperture Radar and measure the planetary gravity...

    ).
  • Laser and radar altimeter
    Altimeter
    An altimeter is an instrument used to measure the altitude of an object above a fixed level. The measurement of altitude is called altimetry, which is related to the term bathymetry, the measurement of depth underwater.-Pressure altimeter:...

    s on satellites have provided a wide range of data. By measuring the bulges of water caused by gravity, they map features on the seafloor to a resolution of a mile or so. By measuring the height and wave-length of ocean waves, the altimeters measure wind speeds and direction, and surface ocean currents and directions.
  • Light detection and ranging (LIDAR) is well known in examples of weapon ranging, laser illuminated homing of projectiles. LIDAR is used to detect and measure the concentration of various chemicals in the atmosphere, while airborne LIDAR can be used to measure heights of objects and features on the ground more accurately than with radar technology. Vegetation remote sensing is a principal application of LIDAR.
  • Radiometer
    Radiometer
    A radiometer is a device for measuring the radiant flux of electromagnetic radiation. Generally, the term radiometer denotes an infrared radiation detector, yet it also includes detectors operating on any electromagnetic wavelength....

    s and photometer
    Photometer
    In its widest sense, a photometer is an instrument for measuring light intensity or optical properties of solutions or surfaces. Photometers are used to measure:*Illuminance*Irradiance*Light absorption*Scattering of light*Reflection of light*Fluorescence...

    s are the most common instrument in use, collecting reflected and emitted radiation in a wide range of frequencies. The most common are visible and infrared sensors, followed by microwave, gamma ray and rarely, ultraviolet. They may also be used to detect the emission spectra of various chemicals, providing data on chemical concentrations in the atmosphere.
  • Stereographic pair
    Stereoscopy
    Stereoscopy refers to a technique for creating or enhancing the illusion of depth in an image by presenting two offset images separately to the left and right eye of the viewer. Both of these 2-D offset images are then combined in the brain to give the perception of 3-D depth...

    s of aerial photographs have often been used to make topographic map
    Topographic map
    A topographic map is a type of map characterized by large-scale detail and quantitative representation of relief, usually using contour lines in modern mapping, but historically using a variety of methods. Traditional definitions require a topographic map to show both natural and man-made features...

    s by imagery and terrain analysts in trafficability and highway departments for potential routes.
  • Simultaneous multi-spectral platforms such as Landsat have been in use since the 70’s. These thematic mappers take images in multiple wavelengths of electro-magnetic radiation (multi-spectral) and are usually found on Earth observation satellite
    Earth observation satellite
    Earth observation satellites are satellites specifically designed to observe Earth from orbit, similar to reconnaissance satellites but intended for non-military uses such as environmental monitoring, meteorology, map making etc....

    s, including (for example) the Landsat program
    Landsat program
    The Landsat program is the longest running enterprise for acquisition of satellite imagery of Earth. On July 26, 1972 the Earth Resources Technology Satellite was launched. This was eventually renamed to Landsat. The most recent, Landsat 7, was launched on April 15, 1999. The instruments on the...

     or the IKONOS
    IKONOS
    IKONOS is a commercial earth observation satellite, and was the first to collect publicly available high-resolution imagery at 1- and 4-meter resolution. It offers multispectral and panchromatic imagery. The IKONOS launch was called by John E. Pike “one of the most significant developments in...

     satellite. Maps of land cover and land use from thematic mapping can be used to prospect for minerals, detect or monitor land usage, deforestation, and examine the health of indigenous plants and crops, including entire farming regions or forests.
  • Hyperspectral imaging
    Hyperspectral imaging
    Hyperspectral imaging collects and processes information from across the electromagnetic spectrum. Much as the human eye sees visible light in three bands , spectral imaging divides the spectrum into many more bands...

     produces an image where each pixel has full spectral information with imaging narrow spectral bands over a contiguous spectral range. Hyperspectral imagers are used in various applications including mineralogy, biology, defence, and environmental measurements.
  • Within the scope of the combat against desertification
    Desertification
    Desertification is the degradation of land in drylands. Caused by a variety of factors, such as climate change and human activities, desertification is one of the most significant global environmental problems.-Definitions:...

    , remote sensing allows to follow-up and monitor risk areas in the long term, to determine desertification factors, to support decision-makers in defining relevant measures of environmental management, and to assess their impacts.

Geodetic

  • Overhead geodetic collection was first used in aerial submarine detection and gravitational data used in military maps. This data revealed minute perturbations in the Earth’s gravitational field
    Gravitational field
    The gravitational field is a model used in physics to explain the existence of gravity. In its original concept, gravity was a force between point masses...

     (geodesy
    Geodesy
    Geodesy , also named geodetics, a branch of earth sciences, is the scientific discipline that deals with the measurement and representation of the Earth, including its gravitational field, in a three-dimensional time-varying space. Geodesists also study geodynamical phenomena such as crustal...

    ) that may be used to determine changes in the mass distribution of the Earth, which in turn may be used for geological studies.

Acoustic and near-acoustic

  • Sonar
    Sonar
    Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...

    : passive sonar, listening for the sound made by another object (a vessel, a whale etc); active sonar, emitting pulses of sounds and listening for echoes, used for detecting, ranging and measurements of underwater objects and terrain.
  • Seismograms taken at different locations can locate and measure earthquake
    Earthquake
    An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...

    s (after they occur) by comparing the relative intensity and precise timing.


To coordinate a series of large-scale observations, most sensing systems depend on the following: platform location, what time it is, and the rotation and orientation of the sensor. High-end instruments now often use positional information from satellite navigation systems. The rotation and orientation is often provided within a degree or two with electronic compasses. Compasses can measure not just azimuth (i. e. degrees to magnetic north), but also altitude (degrees above the horizon), since the magnetic field curves into the Earth at different angles at different latitudes. More exact orientations require gyroscopic-aided orientation
Inertial navigation system
An inertial navigation system is a navigation aid that uses a computer, motion sensors and rotation sensors to continuously calculate via dead reckoning the position, orientation, and velocity of a moving object without the need for external references...

, periodically realigned by different methods including navigation from stars or known benchmarks.

Resolution impacts collection and is best explained with the following relationship: less resolution=less detail & larger coverage, More resolution=more detail, less coverage. The skilled management of collection results in cost-effective collection and avoid situations such as the use of multiple high resolution data which tends to clog transmission and storage infrastructure.

Data processing



Generally speaking, remote sensing works on the principle of the inverse problem. While the object or phenomenon of interest (the state) may not be directly measured, there exists some other variable that can be detected and measured (the observation), which may be related to the object of interest through the use of a data-derived computer model. The common analogy given to describe this is trying to determine the type of animal from its footprints. For example, while it is impossible to directly measure temperatures in the upper atmosphere, it is possible to measure the spectral emissions from a known chemical species (such as carbon dioxide) in that region. The frequency of the emission may then be related to the temperature in that region via various thermodynamic relations.

The quality of remote sensing data consists of its spatial, spectral, radiometric and temporal resolutions.

Spatial resolution: The size of a pixel
Pixel
In digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....

 that is recorded in a raster image
Raster graphics
In computer graphics, a raster graphics image, or bitmap, is a data structure representing a generally rectangular grid of pixels, or points of color, viewable via a monitor, paper, or other display medium...

 – typically pixels may correspond to square areas ranging in side length from 1 to 1000 m (3.3 to 3,280.8 ft).
Spectral resolution: The wavelength width of the different frequency bands recorded – usually, this is related to the number of frequency bands recorded by the platform. Current Landsat collection is that of seven bands, including several in the infra-red spectrum, ranging from a spectral resolution of 0.07 to 2.1 μm. The Hyperion sensor on Earth Observing-1 resolves 220 bands from 0.4 to 2.5 μm, with a spectral resolution of 0.10 to 0.11 μm per band.
Radiometric resolution: The number of different intensities of radiation the sensor is able to distinguish. Typically, this ranges from 8 to 14 bits, corresponding to 256 levels of the gray scale and up to 16,384 intensities or "shades" of colour, in each band. It also depends on the instrument noise
Noise
In common use, the word noise means any unwanted sound. In both analog and digital electronics, noise is random unwanted perturbation to a wanted signal; it is called noise as a generalisation of the acoustic noise heard when listening to a weak radio transmission with significant electrical noise...

.
Temporal resolution: The frequency of flyovers by the satellite or plane, and is only relevant in time-series studies or those requiring an averaged or mosaic image as in deforesting monitoring. This was first used by the intelligence community where repeated coverage revealed changes in infrastructure, the deployment of units or the modification/introduction of equipment. Cloud cover over a given area or object makes it necessary to repeat the collection of said location.

In order to create sensor-based maps, most remote sensing systems expect to extrapolate sensor data in relation to a reference point including distances between known points on the ground. This depends on the type of sensor used. For example, in conventional photographs, distances are accurate in the center of the image, with the distortion of measurements increasing the farther you get from the center. Another factor is that of the platen against which the film is pressed can cause severe errors when photographs are used to measure ground distances. The step in which this problem is resolved is called georeferencing
Georeference
To georeference something means to define its existence in physical space. That is, establishing its location in terms of map projections or coordinate systems. The term is used both when establishing the relation between raster or vector images and coordinates, and when determining the spatial...

, and involves computer-aided matching up of points in the image (typically 30 or more points per image) which is extrapolated with the use of an established benchmark, "warping" the image to produce accurate spatial data. As of the early 1990s, most satellite images are sold fully georeferenced.

In addition, images may need to be radiometrically and atmospherically corrected.

Radiometric correction: gives a scale to the pixel values, e. g. the monochromatic scale of 0 to 255 will be converted to actual radiance values.
Atmospheric correction: eliminates atmospheric haze by rescaling each frequency band so that its minimum value (usually realised in water bodies) corresponds to a pixel value of 0. The digitizing of data also make possible to manipulate the data by changing gray-scale values.

Interpretation is the critical process of making sense of the data. The first application was that of aerial photographic collection which used the following process; spatial measurement through the use of a light table
Light table
A light table is a viewing device that is used to review photographic film or artwork placed on top of it. It provides even illumination of the subject from below through a translucent cover and fluorescent lights that emit little heat. They can also be found mounted on the walls of hospitals and...

 in both conventional single or stereographic coverage, added skills such as the use of photogrammetry, the use of photomosaics, repeat coverage, Making use of objects’ known dimensions in order to detect modifications. Image Analysis is the recently developed automated computer-aided application which is in increasing use.

Object-Based Image Analysis (OBIA) is a sub-discipline of GIScience devoted to partitioning remote sensing (RS) imagery into meaningful image-objects, and assessing their characteristics through spatial, spectral and temporal scale.

Old data from remote sensing is often valuable because it may provide the only long-term data for a large extent of geography. At the same time, the data is often complex to interpret, and bulky to store. Modern systems tend to store the data digitally, often with lossless compression. The difficulty with this approach is that the data is fragile, the format may be archaic, and the data may be easy to falsify. One of the best systems for archiving data series is as computer-generated machine-readable ultrafiche, usually in typefonts such as OCR-B
OCR-B
The OCR-B is a set of monospace font developed in 1968 by Adrian Frutiger for Monotype by following the European Computer Manufacturer's Association standard. Its function was to facilitate the optical character recognition operations by specific electronic devices. It has been accepted as world...

, or as digitized half-tone images. Ultrafiches survive well in standard libraries, with lifetimes of several centuries. They can be created, copied, filed and retrieved by automated systems. They are about as compact as archival magnetic media, and yet can be read by human beings with minimal, standardized equipment.

Data processing levels


To facilitate the discussion of data processing in practice, several processing “levels” were first defined in 1986 by NASA as part of its Earth Observing System
Earth Observing System
The Earth Observing System is a program of NASA comprising a series of artificial satellite missions and scientific instruments in Earth orbit designed for long-term global observations of the land surface, biosphere, atmosphere, and oceans of the Earth. The satellite component of the program was...

 and steadily adopted since then, both internally at NASA (e. g.) and elsewhere (e. g.); these definitions are:
Level Description
0 Reconstructed, unprocessed instrument and payload data at full resolution, with any and all communications artifacts (e. g., synchronization frames, communications headers, duplicate data) removed.
1a Reconstructed, unprocessed instrument data at full resolution, time-referenced, and annotated with ancillary information, including radiometric and geometric calibration coefficients and georeferencing parameters (e. g., platform ephemeris) computed and appended but not applied to the Level 0 data (or if applied, in a manner that level 0 is fully recoverable from level 1a data).
1b Level 1a data that have been processed to sensor units (e. g., radar backscatter cross section, brightness temperature, etc.); not all instruments have Level 1b data; level 0 data is not recoverable from level 1b data.
2 Derived geophysical variables (e. g., ocean wave height, soil moisture, ice concentration) at the same resolution and location as Level 1 source data.
3 Variables mapped on uniform spacetime grid scales, usually with some completeness and consistency (e. g., missing points interpolated, complete regions mosaicked together from multiple orbits, etc).
4 Model output or results from analyses of lower level data (i. e., variables that were not measured by the instruments but instead are derived from these measurements).


A Level 1 data record is the most fundamental (i. e., highest reversible level) data record that has significant scientific utility, and is the foundation upon which all subsequent data sets are produced. Level 2 is the first level that is directly usable for
most scientific applications; its value is much greater than the lower levels. Level 2 data sets tend to be less voluminous than Level 1 data because they have been reduced temporally, spatially, or spectrally. Level 3 data sets are generally smaller than lower level data sets and thus can be dealt with without incurring a great deal of data handling overhead. These data tend to be generally more useful for many applications. The regular spatial and temporal organization of Level 3 datasets makes it feasible to readily combine data from different sources.

History




The modern discipline of remote sensing arose with the development of flight. The balloonist G. Tournachon (alias Nadar
Nadar (photographer)
Félix Nadar was the pseudonym of Gaspard-Félix Tournachon , a French photographer, caricaturist, journalist, novelist and balloonist. Some photographs by Nadar are marked "P. Nadar" for "Photographie Nadar" .-Life: born in April 1820 in Paris...

) made photographs of Paris from his balloon in 1858. Messenger pigeons, kites, rockets and unmanned balloons were also used for early images. With the exception of balloons, these first, individual images were not particularly useful for map making or for scientific purposes.

Systematic aerial photography
Aerial photography
Aerial photography is the taking of photographs of the ground from an elevated position. The term usually refers to images in which the camera is not supported by a ground-based structure. Cameras may be hand held or mounted, and photographs may be taken by a photographer, triggered remotely or...

 was developed for military surveillance and reconnaissance purposes beginning in World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

 and reaching a climax during the Cold War
Cold War
The Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...

 with the use of modified combat aircraft such as the P-51, P-38, RB-66 and the F-4C, or specifically designed collection platforms such as the U2/TR-1
Lockheed U-2
The Lockheed U-2, nicknamed "Dragon Lady", is a single-engine, very high-altitude reconnaissance aircraft operated by the United States Air Force and previously flown by the Central Intelligence Agency . It provides day and night, very high-altitude , all-weather intelligence gathering...

, SR-71, A-5 and the OV-1 series both in overhead and stand-off collection. A more recent development is that of increasingly smaller sensor pods such as those used by law enforcement and the military, in both manned and unmanned platforms. The advantage of this approach is that this requires minimal modification to a given airframe. Later imaging technologies would include Infra-red, conventional, doppler and synthetic aperture radar.

The development of artificial satellites in the latter half of the 20th century allowed remote sensing to progress to a global scale as of the end of the Cold War. Instrumentation aboard various Earth observing and weather satellites such as Landsat
Landsat program
The Landsat program is the longest running enterprise for acquisition of satellite imagery of Earth. On July 26, 1972 the Earth Resources Technology Satellite was launched. This was eventually renamed to Landsat. The most recent, Landsat 7, was launched on April 15, 1999. The instruments on the...

, the Nimbus
Nimbus program
The Nimbus satellites were second-generation U.S. robotic spacecraft used for meteorological research and development. The spacecraft were designed to serve as stabilized, Earth-oriented platforms for the testing of advanced systems to sense and collect atmospheric science data...

 and more recent missions such as RADARSAT
RADARSAT
The RADARSAT constellation is a pair of Canadian Remote Sensing satellites. The constellation consists of:* RADARSAT-1, launched 1995* RADARSAT-2, launched 2007-The Company:...

 and UARS
Upper Atmosphere Research Satellite
The Upper Atmosphere Research Satellite was a NASA-operated orbital observatory whose mission was to study the Earth’s atmosphere, particularly the protective ozone layer. The satellite was deployed from Space Shuttle Discovery during the STS-48 mission on September 15, 1991...

 provided global measurements of various data for civil, research, and military purposes. Space probes to other planets have also provided the opportunity to conduct remote sensing studies in extraterrestrial environments, synthetic aperture radar aboard the Magellan
Magellan probe
The Magellan spacecraft, also referred to as the Venus Radar Mapper, was a 1,035-kilogram robotic space probe launched by NASA on May 4, 1989, to map the surface of Venus using Synthetic Aperture Radar and measure the planetary gravity...

 spacecraft provided detailed topographic maps of Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...

, while instruments aboard SOHO
Solar and Heliospheric Observatory
The Solar and Heliospheric Observatory is a spacecraft built by a European industrial consortium led by Matra Marconi Space that was launched on a Lockheed Martin Atlas IIAS launch vehicle on December 2, 1995 to study the Sun, and has discovered over 2100 comets. It began normal operations in May...

 allowed studies to be performed on the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

 and the solar wind
Solar wind
The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time...

, just to name a few examples.

Recent developments include, beginning in the 1960s and 1970s with the development of image processing
Image processing
In electrical engineering and computer science, image processing is any form of signal processing for which the input is an image, such as a photograph or video frame; the output of image processing may be either an image or, a set of characteristics or parameters related to the image...

 of satellite imagery
Satellite imagery
Satellite imagery consists of photographs of Earth or other planets made by means of artificial satellites.- History :The first images from space were taken on sub-orbital flights. The U.S-launched V-2 flight on October 24, 1946 took one image every 1.5 seconds...

. Several research groups in Silicon Valley
Silicon Valley
Silicon Valley is a term which refers to the southern part of the San Francisco Bay Area in Northern California in the United States. The region is home to many of the world's largest technology corporations...

 including NASA Ames Research Center
NASA Ames Research Center
The Ames Research Center , is one of the United States of America's National Aeronautics and Space Administration 10 major field centers.The centre is located in Moffett Field in California's Silicon Valley, near the high-tech companies, entrepreneurial ventures, universities, and other...

, GTE
GTE
GTE Corporation, formerly General Telephone & Electronics Corporation was the largest independent telephone company in the United States during the days of the Bell System....

 and ESL Inc. developed Fourier transform
Fourier transform
In mathematics, Fourier analysis is a subject area which grew from the study of Fourier series. The subject began with the study of the way general functions may be represented by sums of simpler trigonometric functions...

 techniques leading to the first notable enhancement of imagery data.

Remote Sensing software


Remote Sensing data is processed and analyzed with computer software, known as a remote sensing application
Remote sensing application
A remote sensing application is a software application that processes remote sensing data. Remote sensing applications are similar to graphics software, but they enable generating geographic information from satellite and airborne sensor data. Remote sensing applications read specialized file...

. A large number of proprietary and open source applications exist to process remote sensing data. According to an NOAA Sponsored Research by Global Marketing Insights, Inc. the most used applications among Asian academic groups involved in remote sensing are as follows: ERDAS 36% (ERDAS IMAGINE
ERDAS IMAGINE
ERDAS IMAGINE is a remote sensing application with raster graphics editor capabilities designed by ERDAS for geospatial applications. The latest version is 2010, version 10.1. ERDAS IMAGINE is aimed primarily at geospatial raster data processing and allows the user to prepare, display and enhance...

 25% & ERMapper 11%); ESRI
ESRI
Esri is a software development and services company providing Geographic Information System software and geodatabase management applications. The headquarters of Esri is in Redlands, California....

 30%; ITT Visual Information Solutions ENVI 17%; MapInfo
MapInfo
MapInfo Corporation, initially incorporated as Navigational Technologies Incorporated, was a leading Location Intelligence and GIS company, headquartered in North Greenbush, New York. It was acquired on April 19, 2007 by Pitney Bowes, and on January 28, 2009, the name of division of Pitney Bowes it...

 17%. Among Western Academic respondents as follows: ESRI 39%, ERDAS IMAGINE 27%, MapInfo 9%, AutoDesk
Autodesk
Autodesk, Inc. is an American multinational corporation that focuses on 3D design software for use in the architecture, engineering, construction, manufacturing, media and entertainment industries. The company was founded in 1982 by John Walker, a coauthor of the first versions of the company's...

 7%, ITT Visual Information Solutions ENVI 17%. Other important Remote Sensing Software packages include: TNTmips
TNTmips
TNTmips is a geospatial analysis system providing a fully featured GIS, RDBMS, and automated image processing system with CAD, TIN, surface modeling, map layout and innovative data publishing tools. TNTmips has a single integrated system with an identical interface, functionality, and geodata...

 from MicroImages, PCI Geomatica
PCI Geomatica
PCI Geomatica is a remote sensing desktop software package for processing earth observation data, designed by PCI Geomatics Inc. The latest version of the software is Geomatica 10.3, released in 2010. Geomatica is aimed primarily at raster data processing and allows users to load satellite and...

 made by PCI Geomatics, the leading remote sensing software package in Canada, IDRISI
IDRISI
IDRISI is an integrated geographic information system and remote sensing software developed by Clark Labs at Clark University for the analysis and display of digital geospatial information...

 from Clark Labs, Image Analyst from Intergraph
Intergraph
Intergraph Corporation is an American software development and services company. It provides enterprise engineering and geospatially powered software to businesses, governments, and organizations around the world. Intergraph operates through two divisions: Process, Power & Marine and Security,...

, and RemoteView
RemoteView
RemoteView, is the family name of a group of software programs designed to aid in remote sensing using satellite or aerial images of the Earth's surface. It is published by Overwatch Geospatial Systems , a subsidiary of Textron Inc...

 made by Overwatch Textron Systems. Dragon/ips
Dragon (remote sensing)
Dragon refers to any of several remote sensing image processingsoftware packages. This software provides capabilities for displaying,analyzing, and interpreting digital imagesfrom earth satellites and raster data files...

 is one of the oldest remote sensing packages still available, and is in some cases free. Open source remote sensing software includes GRASS GIS
GRASS GIS
GRASS GIS is a free, open source geographical information system capable of handling raster, topological vector, image processing, and graphic data....

, ILWIS
ILWIS
ILWIS is a GIS / Remote sensing software for both vector and raster processing. ILWIS features include digitizing, editing, analysis and display of data as well as production of quality maps...

, QGIS, OSSIM
OSSIM
OSSIM, or the Open Source Security Information Management, is a collection of tools designed to aid network administrators in computer security, intrusion detection and prevention....

, Opticks (software)
Opticks (software)
Opticks is an open source, remote sensing application that supports imagery, video , Synthetic Aperture Radar , multi-spectral, hyper-spectral, and other types of remote sensing data. Opticks is unlike other remote sensing applications because it treats imagery and video alike...

 and Orfeo toolbox
Orfeo toolbox
Orfeo Toolbox is a library for remote sensing image processing. The project had been initiated by the French space agency in 2006 and is under heavy developments and the participation from the open source community is currently growing. The goal is to provide potential users of satellite images...

.

See also


  • Aerial photography
    Aerial photography
    Aerial photography is the taking of photographs of the ground from an elevated position. The term usually refers to images in which the camera is not supported by a ground-based structure. Cameras may be hand held or mounted, and photographs may be taken by a photographer, triggered remotely or...

  • Airborne Real-time Cueing Hyperspectral Enhanced Reconnaissance
    Airborne Real-time Cueing Hyperspectral Enhanced Reconnaissance
    The Airborne Real-time Cueing Hyperspectral Enhanced Reconnaissance, also known by the acronym ARCHER, is an aerial imaging system that produces ground images far more detailed than plain sight or ordinary aerial photography can....

  • Archaeological imagery
  • Cartography
    Cartography
    Cartography is the study and practice of making maps. Combining science, aesthetics, and technique, cartography builds on the premise that reality can be modeled in ways that communicate spatial information effectively.The fundamental problems of traditional cartography are to:*Set the map's...

  • CLidar
    CLidar
    The CLidar is a scientific instrument used for measuring particulates in the lower atmosphere. CLidar stands for camera lidar, which in turn is an acronym for LIght Detection And Ranging...

  • Coastal management
    Coastal management
    In some jurisdictions the terms sea defense and coastal protection are used to mean, respectively, defense against flooding and erosion...

  • Full Spectral Imaging
    Full Spectral Imaging
    Full spectral imaging is a form of Imaging spectroscopy and is the successor to Hyperspectral imaging. Full Spectral Imaging was developed to improve the capabilities of Earth remote sensing . Hyperspectral imaging acquires data as many contiguous spectral bands. Full Spectral Imaging acquires...

  • Geographic information system
    Geographic Information System
    A geographic information system, geographical information science, or geospatial information studies is a system designed to capture, store, manipulate, analyze, manage, and present all types of geographically referenced data...

     (GIS)
  • Geoinformatics
    Geoinformatics
    Geoinformatics is the science and the technology which develops and uses information science infrastructure to address the problems of geography, geosciences and related branches of engineering.-Overview:...

  • Geophysical survey
    Geophysical survey
    Geophysical survey is the systematic collection of geophysical data for spatial studies. Geophysical surveys may use a great variety of sensing instruments, and data may be collected from above or below the Earth's surface or from aerial or marine platforms. Geophysical surveys have many...

  • Global Positioning System
    Global Positioning System
    The Global Positioning System is a space-based global navigation satellite system that provides location and time information in all weather, anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellites...

     (GPS)
  • Hyperspectral
  • IEEE Geoscience and Remote Sensing Society
  • Imagery Analysis
    Imagery analysis
    Imagery analysis is the extraction of useful information from bi-dimensional graphic formats, including screen shots. This includes color and black-and-white photographs, infra-red photographs and video, radar screens and synthetic aperture radar formats, ultrasound, EKG, EEG, MRI, echo...

  • Imaging Science
    Imaging science
    Imaging science is a multidisciplinary field concerned with the generation, collection, duplication, analysis, modification, and visualization of images . As an evolving field it includes research and researchers from physics, mathematics, electrical engineering, computer vision, computer science,...

  • Land cover
    Land Cover
    Land cover is the physical material at the surface of the earth. Land covers include grass, asphalt, trees, bare ground, water, etc. There are two primary methods for capturing information on land cover: field survey and analysis of remotely sensed imagery....

  • List of Earth observation satellites
  • Liquid crystal tunable filter
    Liquid crystal tunable filter
    Liquid crystal tunable filters are solid-state optical filters that use electronically controlled liquid crystal elements to transmit a selectable wavelength of light and exclude others...

  • Mobile Mapping
    Mobile Mapping
    Mobile mapping is the process of collecting geospatial data from a mobile vehicle, typically fitted with a range of photographic, radar, laser, LiDAR or any number of remote sensing systems. Such systems are composed of an integrated array of time synchronised navigation sensors and imaging sensors...

  • Multispectral pattern recognition
    Multispectral pattern recognition
    Multispectral remote sensing is the collection and analysis of reflected, emitted, or back-scattered energy from an object or an area of interest in multiple bands of regions of the electromagnetic spectrum...

  • National Center for Remote Sensing, Air, and Space Law
  • National LIDAR Dataset
    National LIDAR Dataset
    A National LIDAR Dataset refers to a high-resolution LIDAR dataset comprising most – and ideally all - of a nation’s terrain. Datasets of this type typically meet specified quality standards and are publicly available for free in one or more uniform formats from government or academic sources...

  • Orthophoto
    Orthophoto
    An orthophoto, orthophotograph or orthoimage is an aerial photograph geometrically corrected such that the scale is uniform: the photo has the same lack of distortion as a map...

  • Pictometry
    Pictometry
    Pictometry International Corp. is a Henrietta, New York-based company that provides detailed aerial photography. Its images are taken at a 40 degree angle from low-flying airplanes. Its Electronic Field Study software allows a variety of measurements to be taken directly from the image, including...

  • Sonar
    Sonar
    Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...

  • Radiometry
    Radiometry
    In optics, radiometry is a set of techniques for measuring electromagnetic radiation, including visible light. Radiometric techniques characterize the distribution of the radiation's power in space, as opposed to photometric techniques, which characterize the light's interaction with the human eye...

  • Remote monitoring and control
    Remote monitoring and control
    Remote monitoring and control refers to a field of industrial automation that is entering a new era with the development of wireless sensing devices. Initially limited to SCADA technology, remote monitoring and control refers to the measurement of disparate devices from a network operations center...

  • Remote sensing (archaeology)
    Remote sensing (archaeology)
    Remote sensing techniques in archaeology are an increasingly important component of the technical and methodological tool set available in archaeological research.. The use of remote sensing techniques allows archaeologists to uncover unique data that is unobtainable using traditional...

  • Space probe
    Space probe
    A robotic spacecraft is a spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe. Many space missions are more suited to telerobotic rather than crewed operation, due to...

  • Vector Map
    Vector Map
    The Vector Map , also called Vector Smart Map, is a vector-based collection of Geographic information system data about Earth at various levels of detail. Level 0 coverage is global and entirely in the public domain...

  • TopoFlight
    TopoFlight
    TopoFlight is a three-dimensional flight planning software that was originally conceived by a team of experts in the mapping industry, in use since 2003...