Earth remote sensing

Remote sensing of the Earth (ERS)- Observation of the Earth's surface by aviation and space means equipped with various types of filming equipment. The operating range of wavelengths received by the imaging equipment ranges from fractions of a micrometer (visible optical radiation) to meters (radio waves). Sounding methods can be passive, that is, use the natural reflected or secondary thermal radiation of objects on the Earth's surface, due to solar activity, and active - using stimulated radiation of objects initiated by an artificial source of directional action. Remote sensing data obtained from a spacecraft (SC) are characterized by a large degree of dependence on the transparency of the atmosphere . Therefore, the spacecraft uses multi-channel passive and active equipment that detects electromagnetic radiation in different ranges.

Remote sensing equipment of the first spacecraft launched in the 1960s-70s. was of the track type - the projection of the measurement area on the Earth's surface was a line. Later, remote sensing equipment of a panoramic type appeared and became widespread - scanners, the projection of the measurement area on the Earth's surface of which is a strip.

Earth remote sensing spacecraft are used to study natural resources The Earth and the Solution of Problems of Meteorology. Spacecraft for the study of natural resources are mainly equipped with optical or radar equipment. The advantages of the latter are that it allows observing the Earth's surface at any time of the day, regardless of the state of the atmosphere.

Data processing

The quality of data obtained from remote sensing depends on their spatial, spectral, radiometric and temporal resolution.

Spatial resolution

It is characterized by the size of a pixel (on the surface of the Earth) recorded in a raster image - it can vary from 1 to 1000 meters.

Spectral resolution

Landsat data includes seven bands, including infrared, ranging from 0.07 to 2.1 µm. The Hyperion sensor of Earth Observing-1 is capable of recording 220 spectral bands from 0.4 to 2.5 µm, with a spectral resolution of 0.1 to 0.11 µm.

Radiometric resolution

The number of signal levels that the sensor can register. Usually varies from 8 to 14 bits, which gives from 256 to 16,384 levels. This characteristic also depends on the noise level in the instrument.

Temporary permission

The frequency of the satellite passing over the area of ​​interest. It is of value in the study of series of images, for example, in the study of forest dynamics. Initially, series analysis was carried out for the needs of military intelligence, in particular, to track changes in infrastructure and enemy movements.

To create accurate maps based on remote sensing data, a transformation is needed to eliminate geometric distortions. An image of the Earth's surface with a device directed exactly down contains an undistorted image only in the center of the image. As you move towards the edges, the distances between points on the image and the corresponding distances on the Earth become more and more different. Correction of such distortions is carried out in the process of photogrammetry. Since the early 1990s, most commercial satellite images have been sold already corrected.

In addition, radiometric or atmospheric correction may be required. Radiometric correction converts discrete signal levels, such as 0 to 255, into their true physical values. Atmospheric correction eliminates the spectral distortions introduced by the presence of the atmosphere.

As part of the NASA Earth Observing System program, the levels of remote sensing data processing were formulated:

Level	Description
0	Data coming directly from the device, without overhead (sync frames, headers, repeats).
1a	Reconstructed device data provided with time markers, radiometric coefficients, ephemeris (orbital coordinates) of the satellite.
1b	Level 1a data converted to physical units measurements.
2	Derived geophysical variables (ocean wave height, soil moisture, ice concentration) with the same resolution as Tier 1 data.
3	Variables displayed in the universal space-time scale, possibly supplemented by interpolation.
4	Data obtained as a result of calculations based on previous levels.

see also

Links

• "Messenger" will live in the "Ark". Earth probe. TV spots TV studios of Roskosmos.
• http://www.terralibrary.com/ free space images - see Space Images

Wikimedia Foundation. 2010 .

See what "Remote Sensing of the Earth" is in other dictionaries:

Earth remote sensing- the process of obtaining information about the Earth's surface by observing and measuring from space the own and reflected radiation of elements of the land, ocean and atmosphere in various ranges electromagnetic waves in order to determine the location, ... ... Official terminology

remote sensing- The process of obtaining information about the surface of the Earth and other celestial bodies and objects located on them by non-contact methods - from artificial satellites, aircraft, probes, etc. Geography Dictionary

Collection of information about an object or phenomenon using a recording device that is not in direct contact with this object or phenomenon. The term remote sensing usually includes registration (recording) of electromagnetic ... ... Collier Encyclopedia

Non-contact shooting of the Earth (or other celestial bodies) from ground, airborne, spacecraft, as well as from surface and underwater vessels. The objects of sounding are the surface of land and ocean, geological structures, soil ... ... Geographic Encyclopedia

- (remote sensing), any method of obtaining and recording information from a distance. The most common sensor is CAMERA; such cameras are used in aircraft, satellites and space probes to collect information... Scientific and technical encyclopedic dictionary

remote sensing- remote sensing of the Earth ... Dictionary of abbreviations of the Russian language

Satellite photography photographing the Earth or other planets with the help of satellites. Contents 1 History 2 Use ... Wikipedia

Satellite photography photographing the Earth or other planets with the help of satellites. Contents 1 History 2 Usage 3 Specifications... Wikipedia

Satellite photography photographing the Earth or other planets with the help of satellites. Contents 1 History 2 Use 3 Specifications ... Wikipedia

Books

• Optoelectronic systems of remote sensing. Textbook, V. P. Savinykh, V. A. Solomatin. The fundamentals of the theory, element base, principles of construction, schemes, parameters and characteristics of optoelectronic systems for remote sensing of the Earth are presented: lidars, spectrometers,…

Remote sensing of the Earth (ERS)- Observation of the Earth's surface by aviation and space means equipped with various types of imaging equipment. The operating range of wavelengths received by the imaging equipment ranges from fractions of a micrometer (visible optical radiation) to meters (radio waves). Sounding methods can be passive, that is, using the natural reflected or secondary thermal radiation of objects on the Earth's surface, due to solar activity, and active - using the stimulated radiation of objects initiated by an artificial source of directional action. Remote sensing data obtained from a spacecraft (SC) are characterized by a large degree of dependence on the transparency of the atmosphere. Therefore, the spacecraft uses multi-channel equipment of passive and active types, which detects electromagnetic radiation in various ranges.

Remote sensing equipment of the first spacecraft launched in the 1960s-70s. was of the track type - the projection of the measurement area on the Earth's surface was a line. Later, remote sensing equipment of a panoramic type appeared and became widespread - scanners, the projection of the measurement area on the Earth's surface of which is a strip.

Encyclopedic YouTube

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✪ Earth remote sensing from space

✪ Earth remote sensing

✪ Remote sensing satellite "Resurs-P"

✪ Earth remote sensing from space

✪ [IT lecture]: Is there space beyond geostationary orbit? Prospects for the development of the solar system.

Subtitles

general review

Remote sensing is a method of obtaining information about an object or phenomenon without direct physical contact with this object. Remote sensing is a subset of geography. In the modern sense, the term mainly refers to airborne or spaceborne sensing technologies for the purpose of detecting, classifying and analyzing objects on the earth's surface, as well as the atmosphere and ocean, using propagated signals (for example, electromagnetic radiation). They are divided into active (the signal is first emitted by an aircraft or a space satellite) and passive remote sensing (only a signal from other sources, such as sunlight, is recorded).

Active devices, in turn, emit a signal in order to scan the object and space, after which the sensor is able to detect and measure the radiation reflected or formed by backscattering by the sensing target. Examples of active remote sensing sensors are radar and lidar, which measure the time delay between emitting and registering the returned signal, thus determining the location, speed, and direction of an object.

Remote sensing provides an opportunity to obtain data on dangerous, hard-to-reach and fast-moving objects, and also allows you to conduct observations over vast areas of the terrain. Examples of remote sensing applications would be monitoring deforestation (for example in the Amazon basin), glacier conditions in the Arctic and Antarctic, measuring ocean depth using a lot. Remote sensing also comes to replace expensive and relatively slow methods of collecting information from the Earth's surface, while at the same time guaranteeing the non-interference of man in natural processes in the observed territories or objects.

With orbiting spacecraft, scientists are able to collect and transmit data in various bands of the electromagnetic spectrum, which, combined with larger airborne and ground-based measurements and analysis, provide the necessary range of data to monitor current phenomena and trends, such as El Niño and others. natural phenomena, both in the short and long term. Remote sensing is also of applied importance in the field of geosciences (for example, nature management), agriculture (use and conservation of natural resources), national security(monitoring of border areas).

Data Acquisition Techniques

The main goal of multispectral studies and analysis of the obtained data is objects and territories that emit energy, which makes it possible to distinguish them from the background environment. Short review satellite remote sensing systems is in the overview table.

Generally, the best time to acquire remote sensing data is summer time(in particular, during these months the greatest angle of the sun above the horizon and the greatest duration of the day). An exception to this rule is the acquisition of data using active sensors (eg Radar, Lidar), as well as thermal data in the long wavelength range. In thermal imaging, in which sensors measure thermal energy, it is better to use the time period when the difference between the ground temperature and air temperature is greatest. Thus, the best time for these methods, the cold months, as well as a few hours before dawn at any time of the year.

In addition, there are some other considerations to take into account. With the help of radar, for example, it is impossible to obtain an image of the bare surface of the earth with a thick snow cover; the same can be said about lidar. However, these active sensors are insensitive to light (or lack thereof), making them an excellent choice for high latitude applications (for example). In addition, both radar and lidar are capable (depending on the wavelengths used) of capturing surface images under the forest canopy, making them useful for applications in heavily vegetated regions. On the other hand, spectral data acquisition methods (both stereo imaging and multispectral methods) are applicable mainly on sunny days; data collected in low light conditions tend to have low signal/noise levels, making them difficult to process and interpret. In addition, while stereo imaging is capable of depicting and identifying vegetation and ecosystems, it is not possible with this method (as with multispectral sounding) to penetrate tree canopies and acquire images of the earth's surface.

Application of remote sensing

Remote sensing is most often used in agriculture, geodesy, mapping, monitoring the surface of the earth and the ocean, as well as the layers of the atmosphere.

Agriculture

With the help of satellites, it is possible to receive images of individual fields, regions and districts with a certain cyclicity. Users can receive valuable information about the state of the land, including crop identification, crop area determination and crop status. Satellite data is used to accurately manage and monitor the results of farming at various levels. This data can be used for farm optimization and space-based management of technical operations. The images can help determine the location of crops and the extent of land depletion, and can then be used to develop and implement a treatment plan to locally optimize the use of agricultural chemicals. The main agricultural applications of remote sensing are as follows:

• vegetation:
  • crop type classification
  • assessment of the state of crops (monitoring of agricultural crops, damage assessment)
  • yield assessment
• the soil
  • display of soil characteristics
  • soil type display
  • soil erosion
  • soil moisture
  • mapping tillage practices

Forest cover monitoring

Remote sensing is also used to monitor forest cover and identify species. Maps obtained in this way can cover a large area, while displaying detailed measurements and characteristics of the area (type of trees, height, density). Using remote sensing data, it is possible to define and delineate different forest types, which would be difficult to achieve using traditional methods on the ground surface. The data is available at a variety of scales and resolutions to suit local or regional requirements. The requirements for the detail of the terrain display depend on the scale of the study. To display changes in forest cover (texture, leaf density) apply:

• multispectral images: very high resolution data is needed for accurate species identification
• reusable images of the same territory are used to obtain information about seasonal changes of various types
• stereophotos - to distinguish between species, assess the density and height of trees. Stereo photographs provide a unique view of the forest cover, accessible only through remote sensing technology.
• Radars are widely used in the humid tropics due to their ability to acquire images in all weather conditions.
• Lidars make it possible to obtain a 3-dimensional forest structure, to detect changes in the height of the earth's surface and objects on it. Lidar data helps estimate tree heights, crown areas, and the number of trees per unit area.

Surface monitoring

Surface monitoring is one of the most important and typical applications of remote sensing. The data obtained is used in determining physical condition surface of the earth, for example, forests, pastures, road surfaces, etc., including the results of human activities, such as the landscape in industrial and residential areas, the state of agricultural areas, etc. Initially, a land cover classification system should be established, which usually includes land levels and classes. Levels and classes should be developed taking into account the purpose of use (at the national, regional or local level), the spatial and spectral resolution of remote sensing data, user request, and so on.

Detection of changes in the state of the earth's surface is necessary to update land cover maps and rationalize the use of natural resources. Changes are typically detected when comparing multiple images containing multiple levels of data and, in some cases, when comparing old maps and updated remote sensing images.

• seasonal changes: farmland and deciduous forests change seasonally
• annual change: changes in land surface or land use, such as areas of deforestation or urban sprawl

Land surface information and land cover changes are essential for setting and implementing environmental protection policies and can be used with other data to perform complex calculations (eg erosion risks).

Geodesy

The collection of geodetic data from the air was first used to detect submarines and obtain gravity data used to build military maps. These data are the levels of instantaneous perturbations of the Earth's gravitational field, which can be used to determine changes in the distribution of the Earth's masses, which in turn can be required for various geological studies.

Acoustic and near-acoustic applications

• Sonar: passive sonar, registers sound waves coming from other objects (ship, whale, etc.); active sonar, emits pulses of sound waves and registers the reflected signal. Used to detect, locate and measure the parameters of underwater objects and terrain.
• Seismographs are a special measuring device that is used to detect and record all types of seismic waves. With the help of seismograms taken in different places of a certain territory, it is possible to determine the epicenter of an earthquake and measure its amplitude (after it has occurred) by comparing the relative intensities and the exact time of the oscillations.
• Ultrasound: ultrasonic radiation sensors that emit high-frequency pulses and record the reflected signal. Used to detect waves on the water and determine the water level.

When coordinating a series of large-scale observations, most sounding systems depend on the following factors: the location of the platform and the orientation of the sensors. High quality instruments now often use positional information from satellite navigation systems. Rotation and orientation are often determined by electronic compasses with an accuracy of about one to two degrees. Compasses can measure not only the azimuth (i.e., the degree deviation from magnetic north), but also the height (the deviation from sea level), since the direction of the magnetic field relative to the Earth depends on the latitude at which the observation takes place. For more accurate orientation, it is necessary to use inertial navigation, with periodic corrections by various methods, including navigation by stars or known landmarks.

Overview of the main remote sensing instruments

• Radars are mainly used in air traffic control, early warning, forest cover monitoring, agriculture and large scale meteorological data. Doppler radar is used by law enforcement agencies to monitor vehicle speeds, as well as to obtain meteorological data on wind speed and direction, location and intensity of precipitation. Other types of information received include data on ionized gas in the ionosphere. Artificial aperture interferometric radar is used to obtain accurate digital elevation models of large areas of terrain (see RADARSAT, TerraSAR-X, Magellan).
• Laser and radar altimeters on satellites provide a wide range of data. By measuring ocean level variations caused by gravity, these instruments display seafloor features with a resolution of about one mile. By measuring the height and wavelength of ocean waves with altimeters, you can find out the speed and direction of the wind, as well as the speed and direction of surface ocean currents.
• Ultrasonic (acoustic) and radar sensors are used to measure sea level, tide and tide, determine the direction of waves in coastal marine regions.
• Light Detection and Ranging (LIDAR) technology is well known for its military applications, in particular for laser projectile navigation. LIDAR is also used to detect and measure the concentration of various chemicals in the atmosphere, while LIDAR on board aircraft can be used to measure the height of objects and phenomena on the ground with greater accuracy than can be achieved with radar technology. Vegetation remote sensing is also one of the main applications of LIDAR.
• Radiometers and photometers are the most common instruments used. They capture the reflected and emitted radiation in a wide frequency range. Visible and infrared sensors are the most common, followed by microwave, gamma ray and, less commonly, ultraviolet sensors. These instruments can also be used to detect the emission spectrum of various chemicals, providing data on their concentration in the atmosphere.
• Stereo images obtained from aerial photography are often used in probing vegetation on the Earth's surface, as well as in the construction of topographic maps in the development of potential routes by analyzing images of the terrain, in combination with modeling of environmental features obtained by ground-based methods.
• Multispectral platforms such as Landsat have been in active use since the 1970s. These instruments have been used to generate thematic maps by taking images in multiple wavelengths of the electromagnetic spectrum (multi-spectrum) and are typically used on earth observation satellites. Examples of such missions include the Landsat program or the IKONOS satellite. Land cover and land use maps produced by thematic mapping can be used for mineral exploration, detection and monitoring of land use, deforestation, and study of plant and crop health, including vast tracts of agricultural land or forested areas. Space imagery from the Landsat program is used by regulators to monitor water quality parameters, including Secchi depth, chlorophyll density, and total phosphorus. Weather satellites are used in meteorology and climatology.
• The method of spectral imaging produces images in which each pixel contains complete spectral information, displaying narrow spectral ranges within a continuous spectrum. Spectral imaging devices are used to solve various problems, including those used in mineralogy, biology, military affairs, and measurements of environmental parameters.
• As part of the fight against desertification, remote sensing makes it possible to observe areas that are at risk in the long term, determine the factors of desertification, assess the depth of their impact, and also provide the necessary information to those responsible for making decisions on taking appropriate environmental protection measures.

Data processing

With remote sensing, as a rule, processing of digital data is used, since it is in this format that remote sensing data is currently received. In digital format, it is easier to process and store information. A two-dimensional image in one spectral range can be represented as a matrix (two-dimensional array) of numbers I (i, j), each of which represents the intensity of radiation received by the sensor from the element of the Earth's surface, which corresponds to one image pixel.

The image consists of n x m pixels, each pixel has coordinates (i, j)- line number and column number. Number I (i, j)- an integer and is called the gray level (or spectral brightness) of the pixel (i, j). If the image is obtained in several ranges of the electromagnetic spectrum, then it is represented by a three-dimensional lattice consisting of numbers I (i, j, k), where k- spectral channel number. From a mathematical point of view, it is not difficult to process digital data obtained in this form.

In order to correctly reproduce an image from digital records supplied by information receiving points, it is necessary to know the record format (data structure), as well as the number of rows and columns. Four formats are used, which arrange the data as:

• zone sequence ( Band Sequental, BSQ);
• zones alternating in rows ( Band Interleaved by Line, BIL);
• zones alternating by pixels ( Band Interleaved by Pixel, BIP);
• a sequence of zones with information compression into a file using the group coding method (for example, in jpg format).

AT BSQ-format each zone image is contained in a separate file. This is convenient when there is no need to work with all zones at once. One zone is easy to read and visualize, zone images can be loaded in any order you want.

AT BIL-format zone data is written to one file line by line, with zones alternating in lines: 1st line of the 1st zone, 1st line of the 2nd zone, ..., 2nd line of the 1st zone, 2- th line of the 2nd zone, etc. This entry is convenient when all zones are analyzed simultaneously.

AT BIP-format the zonal values ​​of the spectral brightness of each pixel are stored sequentially: first, the values ​​of the first pixel in each zone, then the values ​​of the second pixel in each zone, and so on. This format is called combined. It is convenient when performing per-pixel processing of a multi-zone image, for example, in classification algorithms.

Group coding used to reduce the amount of raster information. Such formats are convenient for storing large snapshots; to work with them, you need to have a data unpacking tool.

Image files usually come with the following additional image-related information:

• description of the data file (format, number of rows and columns, resolution, etc.);
• statistical data (brightness distribution characteristics - minimum, maximum and average value, dispersion);
• map projection data.

Additional information is contained either in the header of the image file or in a separate text file with the same name as the image file.

According to the degree of complexity, the following levels of processing of CS provided to users are distinguished:

• 1A is a radiometric correction of distortions caused by differences in sensitivity of individual sensors.
• 1B - radiometric correction at processing level 1A and geometric correction of systematic sensor distortions, including panoramic distortions, distortions caused by the rotation and curvature of the Earth, fluctuations in the height of the satellite orbit.
• 2A - image correction at level 1B and correction in accordance with a given geometric projection without the use of ground control points. For geometric correction, a global digital elevation model is used ( DEM, DEM) with a step on the ground of 1 km. The geometric correction used eliminates systematic sensor distortions and projects the image into a standard projection ( UTM WGS-84), using known parameters (satellite ephemeris data, spatial position, etc.).
• 2B - image correction at level 1B and correction in accordance with a given geometric projection using control ground points;
• 3 - image correction at the 2B level plus correction using terrain DEM (ortho-rectification).
• S - image correction using a reference image.

The quality of data obtained from remote sensing depends on their spatial, spectral, radiometric and temporal resolution.

Spatial resolution

It is characterized by the size of a pixel (on the surface of the Earth), recorded in a raster image - usually varies from 1 to 4000 meters.

Spectral resolution

Landsat data includes seven bands, including infrared, ranging from 0.07 to 2.1 µm. The Hyperion sensor of Earth Observing-1 is capable of recording 220 spectral bands from 0.4 to 2.5 µm, with a spectral resolution of 0.1 to 0.11 µm.

Radiometric resolution

The number of signal levels that the sensor can register. Usually varies from 8 to 14 bits, which gives from 256 to 16,384 levels. This characteristic also depends on the noise level in the instrument.

Temporary permission

The frequency of the satellite passing over the area of ​​interest. It is of value in the study of series of images, for example, in the study of forest dynamics. Initially, series analysis was carried out for the needs of military intelligence, in particular, to track changes in infrastructure and enemy movements.

To create accurate maps based on remote sensing data, a transformation is needed to eliminate geometric distortions. An image of the Earth's surface with a device directed exactly down contains an undistorted image only in the center of the image. As you move towards the edges, the distances between points on the image and the corresponding distances on the Earth become more and more different. Correction of such distortions is carried out in the process of photogrammetry. Since the early 1990s, most commercial satellite images have been sold already corrected.

In addition, radiometric or atmospheric correction may be required. Radiometric correction converts discrete signal levels, such as 0 to 255, into their true physical values. Atmospheric correction eliminates the spectral distortions introduced by the presence of the atmosphere.

As part of the NASA Earth Observing System program, the levels of remote sensing data processing were formulated:

Level	Description
0	Data coming directly from the device, without overhead (sync frames, headers, repeats).
1a	Reconstructed device data provided with time markers, radiometric coefficients, ephemeris (orbital coordinates) of the satellite.
1b	Level 1a data converted to physical units.
2	Derived geophysical variables (ocean wave height, soil moisture, ice concentration) with the same resolution as Tier 1 data.
3	Variables displayed in the universal space-time scale, possibly supplemented by interpolation.
4	Data obtained as a result of calculations based on previous levels.

Training and education

In most higher educational institutions remote sensing training is carried out at the departments of geography. The relevance of remote sensing is constantly increasing in the modern information society. This discipline is one of the key technologies of the aerospace industry and is of great economic importance - for example, the new TerraSAR-X and RapidEye sensors are constantly being developed, and the demand for skilled labor is also constantly growing. In addition, remote sensing has an extremely large impact on everyday life ranging from weather reports to forecasting climate change and natural disasters. As an example, 80% of German students use Google Earth; in 2006 alone, the program was downloaded 100 million times. However, studies show that only a small fraction of these users have fundamental knowledge of the data they work with. On the this moment There is a huge knowledge gap between the use and understanding of satellite imagery. The teaching of remote sensing principles is very superficial in the vast majority of educational institutions, despite the urgent need to improve the quality of teaching in this subject. Many of the computer software products specifically designed for the study of remote sensing have not yet been implemented in educational system mainly due to its complexity. Thus, in many cases, this discipline is either not included at all in curriculum or does not include the course scientific analysis analog images. In practice, the subject of remote sensing requires a consolidation of physics and mathematics, as well as a high level of competence in the use of tools and techniques other than simple visual interpretation of satellite images.

Remote sensing of the Earth (ERS) - obtaining information about the surface of the Earth and objects on it, the atmosphere, the ocean, the upper layer of the earth's crust by non-contact methods, in which the recording device is removed from the object of research at a considerable distance. General physical basis remote sensing is a functional relationship between the registered parameters of the object's own or reflected radiation, its biogeophysical characteristics and spatial position. The essence of the method is to interpret the results of measuring electromagnetic radiation, which is reflected or emitted by an object and is recorded at some point in space remote from it.

Remote sensing methods have been used in Earth exploration for a very long time. Initially, drawn photographs were used, which fixed the spatial arrangement of the studied objects. With the invention of photography, terrestrial phototheodolite survey arose, in which maps of mountainous regions were compiled from perspective photographs. The development of aviation ensured the receipt of aerial photographs depicting the terrain from above, in plan. This armed the earth sciences with a powerful means of research - aerial methods.

The concept of remote sensing appeared in the 19th century following the invention of photography, and one of the first areas in which this method began to be applied was astronomy. Subsequently, remote sensing began to be used in the military field to collect information about the enemy and make strategic decisions. During civil war in the United States, photographs taken by unmanned aerial vehicles served to monitor the movement of troops, the supply of supplies, the progress of fortification work, and to assess the effect of artillery shelling. As a result of research funded by various states, technologies were developed that made it possible to create sensors, first for military purposes, and then for civilian applications of this method. After the Second World War, the remote sensing method began to be used for monitoring the environment and assessing the development of territories, as well as in civilian cartography. In the 60s of the XX century, with the advent of space rockets and satellites, remote sensing went into space.

A new era of remote sensing is associated with manned space flights, reconnaissance, meteorological and resource satellites.

The capabilities of remote sensing in the military field increased significantly after 1960 as a result of the launch of reconnaissance satellites as part of the CORONA, ARGON, LANYARD programs, the purpose of which was to obtain photographs from low orbits. Soon, stereo pairs of images with a resolution of 2 meters were obtained. The first satellites worked in orbit for seven to eight days, but the next generations of these devices were able to supply data for several months.

As a result of the implementation of manned flight programs that were launched in the United States in 1961, a man first landed on the surface of the moon (1969). It should be noted the Mercury program, within the framework of which images of the Earth were obtained, the systematic collection of remote sensing data during the Gemini project (1965-1966), the Apollo program (1968-1975), during which remote sensing of the earth's surface (ERS) was carried out ) and the landing of a man on the moon took place, the launch of the Skylab space station (1973-1974), on which studies of earth resources were carried out, flights spaceships reusable, which began in 1981, as well as obtaining multi-zone images with a resolution of 100 meters in the visible and near infrared range using nine spectral bands.

In the Soviet Union, and then in Russia, space programs developed in parallel with the US space programs. The flight of Yuri Gagarin on April 12, 1961, which became the first manned flight into space, the launches of the Vostok (1961-1963), Voskhod (1964-1965) and Soyuz spacecraft, work in orbit of space stations " Salut "(for the first time on April 19, 1971).

The first meteorological satellite was launched in the United States on April 1, 1960. It was used for weather forecasting, monitoring the movement of cyclones, and other similar tasks. TIROS-1 (Television and Infrared Observation Satellite) was the first among the satellites that were used to regularly survey large areas of the earth's surface.

The first dedicated satellite was launched in 1972. It was called ERTS-1 (Earth Resources Technology Satellite) and was used mainly for agricultural purposes. Currently, the satellites of this series are called Landsat.

They are designed for regular multi-zonal survey of territories with medium resolution. Later, in 1978, the first satellite with the SEASAT scanning system was launched, but it transmitted data for only three months. The first French satellite of the SPOT series, with which it was possible to obtain stereo pairs of images, was launched into orbit in 1985. The launch of the first Indian remote sensing satellite, called IRS (Indian Remote Sensing), took place in 1988. Japan also launched its JERS MOS satellites into orbit.

Since 1975, China has periodically launched its own satellites, but the data they receive is still in the public domain. The European Space Consortium launched its ERS radar satellites in 1991 and 1995, and Canada launched its RADARSAT satellite in 1995.

The history of the development of aerospace methods indicates that new achievements in science and technology are immediately used to improve imaging technologies. This happened in the middle of the 20th century, when such innovations as computers, spacecraft, radio-electronic survey systems made revolutionary changes in traditional aerial photo methods - aerospace sounding was born. Space images have provided geo-information for solving problems at the regional and global levels.

At present, the following trends in the progressive development of aerospace sounding are clearly manifested.

• Space images, promptly posted on the Internet, are becoming the most popular video information about the area for both professional professionals and the general public.
• The resolution and metric properties of open access satellite images are rapidly increasing. Ultra-high resolution orbital images - meter and even decimeter - are gaining distribution, which successfully compete with aerial photographs.
• Analog photographic images and traditional processing technologies are losing their former monopoly value. The main processing device was a computer equipped with specialized software and peripherals.
• The development of all-weather radar turns it into a progressive method for obtaining metrically accurate spatial geoinformation, which begins to be effectively integrated with optical technologies for aerospace sounding.
• A market for a variety of aerospace Earth sensing products is rapidly emerging. The number of commercial spacecraft operating in orbits, especially foreign ones, is steadily increasing. The images obtained by the resource satellite systems Landsat (USA), SPOT (France), IRS (India), mapping satellites ALOS (Japan), Cartosat (India), ultra-high resolution satellites Ikonos, QiuckBird, GeoEye (USA), including including radar TerraSAR-X and TanDEM-X (Germany), performing tandem interferometric survey. The system of space monitoring satellites RapidEye (Germany) is successfully operated.

An aerospace image is a two-dimensional image of real objects, which is obtained according to certain geometric and radiometric (photometric) laws by remote registration of the brightness of objects and is intended to study visible and hidden objects, phenomena and processes of the surrounding world, as well as to determine their spatial position.

The range of scales of modern aerospace images is huge: it can vary from 1:1000 to 1:100,000,000, i.e. a hundred thousand times. At the same time, the most common scales of aerial photographs lie within 1:10,000 - 1:50,000, and space ones - 1:200,000 - 1:10,000,000. All aerospace images are usually divided into analog (usually photographic) and digital (electronic). The image of digital photographs is formed from separate identical elements - pixels (from the English Picture element-pxel); the brightness of each pixel is characterized by one number.

Aerospace images as information models of the terrain are characterized by a number of properties, among which are pictorial, radiometric (photometric) and geometric. Visual properties characterize the ability of photographs to reproduce fine details, colors and tonal gradations of objects, radiometric ones indicate the accuracy of quantitative registration of the brightness of objects by an image, geometric properties characterize the possibility of determining the sizes, lengths and areas of objects and their relative position from images.

The best way to use Earth observation data from satellites is to analyze them together with information from other sources.

Obtaining images with overlap from several consecutive points of the orbit (stereo imaging) allows you to get a more accurate representation of three-dimensional objects and increase the signal-to-noise ratio.

The use of multizonal images is based on the uniqueness of the tonal characteristics of various objects. Combining brightness data from images in different spectral ranges allows you to accurately identify certain spatial structures. Shooting using a large number(more than 10) narrow shooting areas are called hyperspectral. With hyperspectral imaging, the possibility of identifying objects characterized by the presence of absorption bands increases, which is typical, for example, for pollution. Multi-zone and hyperspectral surveys make it possible to more effectively use differences in the spectral brightness of surveyed objects for their interpretation.

This type of images can also include radar images obtained both when registering reflected radio waves of different lengths, and with their different polarizations.

Multi-time survey is a scheduled survey on predetermined dates that allows you to perform comparative analysis images of those objects whose characteristics change over time.

Multi-level survey - survey with different sampling levels is used to obtain more detailed information about the study area.

As a rule, the whole process of data collection is divided into three levels: satellite imagery, aerial photography and ground surveys.

Images obtained by the method of multipolarization shooting are used to draw boundaries between objects based on differences in the polarization properties of the reflected radiation. Thus, for example, reflected radiation from a water surface is usually more strongly polarized than reflected radiation from vegetation.

The combined method consists in the use of multi-time, multi-zonal and multi-polarization surveys.

It is difficult to imagine the effective work of modern GIS without satellite methods for studying the territories of our planet. Remote satellite sensing has found wide application in geo information technology as in connection with rapid development and the improvement of space technology, as well as the curtailment of aviation and ground-based monitoring methods.

remote sensing(DZ) is a scientific direction based on the collection of information about the Earth's surface without actual contact with it.

The process of obtaining surface data includes probing and recording information about the energy reflected or emitted by objects for subsequent processing, analysis and practical use. The DZ process is presented on and consists of the following elements:

Rice. . Stages of DZ.

Having a source of power or lighting (A) is the first requirement for remote sensing, i.e. there must be a source of energy that illuminates or energizes electromagnetic field objects of interest for research.

Radiation and atmosphere (B) - radiation propagating from the source to the object, part of the way passes through the Earth's atmosphere. This interaction must be taken into account, since the characteristics of the atmosphere affect the parameters of energy radiation.

Interaction with the object of study (C) - the nature of the interaction of the radiation incident on the object strongly depends on the parameters of both the object and the radiation.

Registration of energy by the sensor (D) - the radiation emitted by the object of study falls on a remote highly sensitive sensor, and then the information received is recorded on the media.

Transmission, reception and processing of information (E) - the information collected by the sensitive sensor is transmitted in digital form to the receiving station, where the data is transformed into an image.

Interpretation and analysis (F) - the processed image is interpreted visually or with the help of a computer, after which information about the object under study is extracted from it.

Application of the received information (G) - the remote sensing process reaches completion when we obtain the necessary information regarding the object of observation for a better understanding of its characteristics and behavior, i.e. when a practical problem is solved.

The following areas of application of satellite remote sensing (SRS) are distinguished:

Obtaining information on the state of the environment and land use; assessment of the yield of agricultural land;

Study of flora and fauna;

Assessment of the consequences of natural disasters (earthquakes, floods, fires, epidemics, volcanic eruptions);

Assessment of damage in case of pollution of land and water bodies;

Oceanology.

SDZ means allow obtaining information about the state of the atmosphere not only locally, but also globally. Sounding data comes in the form of images, usually in digital form. Further processing is carried out by a computer. Therefore, the issue of SDZ is closely related to the tasks of digital image processing.

To observe our planet from space, remote methods are used, in which the researcher has the opportunity to obtain information about the object under study at a distance. Remote sensing methods, as a rule, are indirect, that is, they measure parameters that are not of interest to the observer, but some quantities associated with them. For example, we need to assess the state of forests in the Ussuri taiga. The satellite equipment involved in monitoring will register only the intensity of the light flux from the objects under study in several parts of the optical range. To decipher such data, preliminary studies are required, including various experiments on the study of the state of individual trees by contact methods. Then it is necessary to determine how the same objects look from the aircraft, and only after that to judge the state of the forests from satellite data.

It is no coincidence that methods of studying the Earth from space are classified as high-tech. This is due not only to the use of rocket technology, complex optoelectronic devices, computers, high-speed information networks, but also to a new approach to obtaining and interpreting measurement results. Satellite studies are carried out over a small area, but they make it possible to generalize data over vast expanses and even over the entire globe. Satellite methods, as a rule, allow obtaining results in a relatively short time interval. For example, for boundless Siberia, satellite methods are the most acceptable.

Among the features of remote methods is the influence of the medium (atmosphere) through which the signal from the satellite passes. For example, the presence of clouds covering objects makes them invisible in the optical range. But even in the absence of clouds, the atmosphere attenuates the radiation from objects. Therefore, satellite systems have to work in the so-called transparency windows, taking into account that absorption and scattering by gases and aerosols take place in them. In the radio range, it is possible to observe the Earth through clouds.

Information about the Earth and its objects comes from satellites in digital form. Terrestrial digital image processing is carried out using computers. Modern satellite methods allow not only to obtain an image of the Earth. Using sensitive instruments, it is possible to measure the concentration of atmospheric gases, including those that cause the greenhouse effect. The Meteor-3 satellite with the TOMS device installed on it made it possible to assess the state of the entire ozone layer of the Earth in a day. The NOAA satellite, in addition to obtaining surface images, makes it possible to study the ozone layer and study the vertical profiles of atmospheric parameters (pressure, temperature, humidity).

Remote methods are divided into active and passive. Using active methods the satellite sends a signal of its own energy source (laser, radar transmitter) to the Earth, registers its reflection, Fig. 3.4a. Passive methods involve the registration of solar energy reflected from the surface of objects or the thermal radiation of the Earth.

Rice. . Active (a) and passive (b) remote sensing methods.

Remote sensing of the Earth from space uses the optical range of electromagnetic waves and the microwave portion of the radio range. The optical range includes the ultraviolet (UV) part of the spectrum; visible area - blue (B), green (G) and red (R) stripes; infrared (IR) - near (NIR), medium and thermal.

With passive methods of sounding in the optical range, the sources of electromagnetic energy are solid, liquid, gaseous bodies heated to a sufficiently high temperature.

At wavelengths longer than 4 μm, the Earth's own thermal radiation exceeds that of the Sun. By registering the intensity of the Earth's thermal radiation from space, it is possible to accurately estimate the temperature of the land and water surface, which is the most important ecological characteristic. By measuring the temperature of the cloud top, one can determine its height, given that in the troposphere the temperature decreases with height by an average of 6.5 o /km. When registering thermal radiation from satellites, the wavelength range of 10-14 microns is used, in which the absorption in the atmosphere is small. At the temperature of the earth's surface (clouds) equal to –50o, the radiation maximum falls at 12 µm, at +50o - at 9 µm.