Imaging radar is an application of radar which is used to create two-dimensional images , typically of landscapes. Imaging radar provides its light to illuminate an area on the ground and take a picture at radio wavelengths. It uses an antenna and digital computer storage to record its images. In a radar image, one can see only the energy that was reflected back towards the radar antenna. The radar moves along a flight path and the area illuminated by the radar, or footprint, is moved along the surface in a swath, building the image as it does so.
54-542: TerraSAR-X is an imaging radar Earth observation satellite , a joint venture being carried out under a public-private-partnership between the German Aerospace Center (DLR) and EADS Astrium . The exclusive commercial exploitation rights are held by the geo-information service provider Astrium . TerraSAR-X was launched on 15 June 2007 and has been in operational service since January 2008. With its twin satellite TanDEM-X , launched 21 June 2010, TerraSAR-X acquires
108-435: A piezometer . Aquifers are also described in terms of hydraulic conductivity, storativity and transmissivity. There are a number of geophysical methods for characterizing aquifers. There are also problems in characterizing the vadose zone (unsaturated zone). Infiltration is the process by which water enters the soil. Some of the water is absorbed, and the rest percolates down to the water table . The infiltration capacity,
162-513: A few hundred metres and record data synchronously. This twin satellite constellation will allow the generation of WorldDEM, the global digital elevation models (DEMs). With higher accuracy, coverage and quality – WorldDEM is a consistent DEM of the Earth's land surface is envisaged to be acquired and generated within three years after launch. Available from 2014, WorldDEM is to feature a vertical accuracy of 2 m (relative) and 10 m (absolute), within
216-638: A horizontal raster of approximately 12×12 square meters, slightly varying depending on the geographic latitude. Radar stands for Radio Detection and Ranging and traditionally contains: Satellite radar systems came into operation over fifteen years after the adoption of optical camera systems. The resolution is lower than optical imaging, but radar can gather information at any time of the day or night and independent of cloud cover . Early radar satellite techniques were altimetry (measuring height over sea level), NASA's SEASAT (launched in 1978), study of waves/wind or soil data. The military has used radar since
270-402: A more global approach to the understanding of the behavior of hydrologic systems to make better predictions and to face the major challenges in water resources management. Water movement is a significant means by which other materials, such as soil, gravel, boulders or pollutants, are transported from place to place. Initial input to receiving waters may arise from a point source discharge or
324-451: A prediction in practical applications. Ground water is water beneath Earth's surface, often pumped for drinking water. Groundwater hydrology ( hydrogeology ) considers quantifying groundwater flow and solute transport. Problems in describing the saturated zone include the characterization of aquifers in terms of flow direction, groundwater pressure and, by inference, groundwater depth (see: aquifer test ). Measurements here can be made using
378-414: A sharp beam. The sharpness of the beam defines the azimuth resolution. An airborne radar could collect data while flying this distance and process the data as if it came from a physically long antenna. The distance the aircraft flies in synthesizing the antenna is known as the synthetic aperture. A narrow synthetic beam width results from the relatively long synthetic aperture, which gets finer resolution than
432-420: A smaller physical antenna. Inverse synthetic aperture radar (ISAR) is another kind of SAR system which can produce high-resolution on two- and three-dimensional images. An ISAR system consists of a stationary radar antenna and a target scene that is undergoing some motion. ISAR is theoretically equivalent to SAR in that high-azimuth resolution is achieved via relative motion between the sensor and object, yet
486-416: A target with a laser and analyzing the reflected light. Laser radar is used for multi-dimensional imaging and information gathering. In all information gathering modes, lasers that transmit in the eye-safe region are required as well as sensitive receivers at these wavelengths. 3-D imaging requires the capacity to measure the range to the first scatter within every pixel. Hence, an array of range counters
540-419: Is a form of radar that transmits a narrow angle beam of pulse radio wave in the range direction at right angles to the flight direction and receives the backscattering from the targets which will be transformed to a radar image from the received signals. Usually the reflected pulse will be arranged in the order of return time from the targets, which corresponds to the range direction scanning. The resolution in
594-413: Is a form of radar which moves a real aperture or antenna through a series of positions along the objects to provide distinctive long-term coherent-signal variations. This can be used to obtain higher resolution. SARs produce a two-dimensional (2-D) image. One dimension in the image is called range and is a measure of the "line-of-sight" distance from the radar to the object. Range is determined by measuring
SECTION 10
#1732859461901648-402: Is affected by the interaction of dissolved oxygen with organic material and various chemical transformations that may take place. Measurements of water quality may involve either in-situ methods, in which analyses take place on-site, often automatically, and laboratory-based analyses and may include microbiological analysis . Observations of hydrologic processes are used to make predictions of
702-769: Is an important part of the water cycle. It is partly affected by humidity, which can be measured by a sling psychrometer . It is also affected by the presence of snow, hail, and ice and can relate to dew, mist and fog. Hydrology considers evaporation of various forms: from water surfaces; as transpiration from plant surfaces in natural and agronomic ecosystems. Direct measurement of evaporation can be obtained using Simon's evaporation pan . Detailed studies of evaporation involve boundary layer considerations as well as momentum, heat flux, and energy budgets. Remote sensing of hydrologic processes can provide information on locations where in situ sensors may be unavailable or sparse. It also enables observations over large spatial extents. Many of
756-502: Is needed. A monolithic approach to an array of range counters is being developed. This technology must be coupled with highly sensitive detectors of eye-safe wavelengths. To measure Doppler information requires a different type of detection scheme than is used for spatial imaging. The returned laser energy must be mixed with a local oscillator in a heterodyne system to allow extraction of the Doppler shift. Synthetic-aperture radar (SAR)
810-402: Is often adequate to discriminate between various missiles, military aircraft, and civilian aircraft. Rolling is side to side. Pitching is forward and backwards, yawing is turning left or right. Monopulse radar 3-D imaging technique uses 1-D range image and monopulse angle measurement to get the real coordinates of each scatterer. Using this technique, the image doesn't vary with the change of
864-489: Is only one of many important aspects within those fields. Hydrological research can inform environmental engineering, policy , and planning . Hydrology has been subject to investigation and engineering for millennia. Ancient Egyptians were one of the first to employ hydrology in their engineering and agriculture, inventing a form of water management known as basin irrigation. Mesopotamian towns were protected from flooding with high earthen walls. Aqueducts were built by
918-580: Is thought of as starting at the land-atmosphere boundary and so it is important to have adequate knowledge of both precipitation and evaporation. Precipitation can be measured in various ways: disdrometer for precipitation characteristics at a fine time scale; radar for cloud properties, rain rate estimation, hail and snow detection; rain gauge for routine accurate measurements of rain and snowfall; satellite for rainy area identification, rain rate estimation, land-cover/land-use, and soil moisture, snow cover or snow water equivalent for example. Evaporation
972-513: Is utilized to formulate operating rules for large dams forming part of systems which include agricultural, industrial and residential demands. Hydrological models are simplified, conceptual representations of a part of the hydrologic cycle. They are primarily used for hydrological prediction and for understanding hydrological processes, within the general field of scientific modeling . Two major types of hydrological models can be distinguished: Recent research in hydrological modeling tries to have
1026-412: Is valued for combining all the benefits of camera, LIDAR, thermal imaging and ultrasonic technologies, with additional benefits: Hydrology Hydrology (from Ancient Greek ὕδωρ ( húdōr ) 'water' and -λογία ( -logía ) 'study of') is the scientific study of the movement, distribution, and management of water on Earth and other planets, including
1080-449: The Doppler effect caused by the rotation or other motion of the object and by the changing view of the object brought about by the relative motion between the object and the back-scatter that is perceived by the radar of the object (typically, a plane) flying over the earth. Through recent improvements of the techniques, radar imaging is getting more accurate. Imaging radar has been used to map
1134-618: The Greeks and Romans , while history shows that the Chinese built irrigation and flood control works. The ancient Sinhalese used hydrology to build complex irrigation works in Sri Lanka , also known for the invention of the Valve Pit which allowed construction of large reservoirs, anicuts and canals which still function. Marcus Vitruvius , in the first century BC, described a philosophical theory of
SECTION 20
#17328594619011188-399: The return period of such events. Other quantities of interest include the average flow in a river, in a year or by season. These estimates are important for engineers and economists so that proper risk analysis can be performed to influence investment decisions in future infrastructure and to determine the yield reliability characteristics of water supply systems. Statistical information
1242-799: The water cycle , water resources , and drainage basin sustainability. A practitioner of hydrology is called a hydrologist . Hydrologists are scientists studying earth or environmental science , civil or environmental engineering , and physical geography . Using various analytical methods and scientific techniques, they collect and analyze data to help solve water related problems such as environmental preservation , natural disasters , and water management . Hydrology subdivides into surface water hydrology, groundwater hydrology ( hydrogeology ), and marine hydrology. Domains of hydrology include hydrometeorology , surface hydrology , hydrogeology , drainage-basin management, and water quality . Oceanography and meteorology are not included because water
1296-455: The 20th century, while governmental agencies began their own hydrological research programs. Of particular importance were Leroy Sherman's unit hydrograph , the infiltration theory of Robert E. Horton , and C.V. Theis' aquifer test/equation describing well hydraulics. Since the 1950s, hydrology has been approached with a more theoretical basis than in the past, facilitated by advances in the physical understanding of hydrological processes and by
1350-721: The Earth's surface ( plate tectonics , volcanism , earthquake) are further scientific fields of application. To ensure the commercial success of the mission, EADS Astrium founded its 100% subsidiary Infoterra in 2001; the company being responsible for establishing a commercial market for TerraSAR-X data as well as TerraSAR-X-based geo-information products and services. Radars on the Space Shuttle : (the TerraSAR-X authors were involved in SRL and SRTM missions) Imaging radar Digital radar images are composed of many dots. Each pixel in
1404-462: The Earth, other planets, asteroids, other celestial objects and to categorize targets for military systems. An imaging radar is a kind of radar equipment which can be used for imaging. A typical radar technology includes emitting radio waves, receiving their reflection, and using this information to generate data. For an imaging radar, the returning waves are used to create an image. When the radio waves reflect off objects, this will make some changes in
1458-537: The ISAR moving target scene is usually made up of non cooperative objects. Algorithms with more complex schemes for motion error correction are needed for ISAR imaging than those needed in SAR. ISAR technology uses the movement of the target rather than the emitter to make the synthetic aperture. ISAR radars are commonly used on vessels or aircraft and can provide a radar image of sufficient quality for target recognition. The ISAR image
1512-668: The Institute for High-Frequency Engineering and Radar Systems (HR) which are all part of the DLR. Applications of the high-resolution TerraSAR-X radar imagery include: The scientific use of the TerraSAR-X data will be coordinated through the TerraSAR-X Science Service System by the DLR. The new-quality data records, as provided by TerraSAR-X, will offer a vast amount of new research incentives, for instance in ecology, geology, hydrology and oceanography . The smallest movements of
1566-560: The advent of computers and especially geographic information systems (GIS). (See also GIS and hydrology ) The central theme of hydrology is that water circulates throughout the Earth through different pathways and at different rates. The most vivid image of this is in the evaporation of water from the ocean, which forms clouds. These clouds drift over the land and produce rain. The rainwater flows into lakes, rivers, or aquifers. The water in lakes, rivers, and aquifers then either evaporates back to
1620-530: The atmosphere or eventually flows back to the ocean, completing a cycle. Water changes its state of being several times throughout this cycle. The areas of research within hydrology concern the movement of water between its various states, or within a given state, or simply quantifying the amounts in these states in a given region. Parts of hydrology concern developing methods for directly measuring these flows or amounts of water, while others concern modeling these processes either for scientific knowledge or for making
1674-467: The data basis for the WorldDEM , the worldwide and homogeneous DEM available from 2014. Using a phased array synthetic aperture radar (SAR) antenna ( X-band wavelength 31mm, frequency 9.65 GHz), TerraSAR-X provides radar images of the entire planet from an Earth polar orbit of 514km altitude. This is selected so that the satellite follows a Sun-synchronous orbit . This specific orbit means that
TerraSAR-X - Misplaced Pages Continue
1728-605: The following three main imaging modes: In addition, the design of TerraSAR-X's SAR antenna allows a variety of polarimetric combinations: single or dual polarization, or full polarimetric data takes. Depending on the desired application, one of four different processing levels is selected: TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurements) is a second, similar spacecraft launched on 21 June 2010 from Baikonur Cosmodrome in Kazakhstan. Since October 2010, TerraSAR-X and TanDEM-X have orbited in close formation at distances of
1782-685: The future behavior of hydrologic systems (water flow, water quality). One of the major current concerns in hydrologic research is "Prediction in Ungauged Basins" (PUB), i.e. in basins where no or only very few data exist. The aims of Statistical hydrology is to provide appropriate statistical methods for analyzing and modeling various parts of the hydrological cycle. By analyzing the statistical properties of hydrologic records, such as rainfall or river flow, hydrologists can estimate future hydrologic phenomena. When making assessments of how often relatively rare events will occur, analyses are made in terms of
1836-413: The hydrologic cycle, in which precipitation falling in the mountains infiltrated the Earth's surface and led to streams and springs in the lowlands. With the adoption of a more scientific approach, Leonardo da Vinci and Bernard Palissy independently reached an accurate representation of the hydrologic cycle. It was not until the 17th century that hydrologic variables began to be quantified. Pioneers of
1890-446: The image obtained by monopulse radar 3-D imaging is the physical image which is consistent with the real size of the object. 4D imaging radar leverages a Multiple Input Multiple Output (MiMo) antenna array for high-resolution detection, mapping and tracking of multiple static and dynamic targets simultaneously. It combines 3D imaging with Doppler analysis to create the additional dimension – velocity. A 4D imaging radar system measures
1944-430: The important areas of hydrology is the interchange between rivers and aquifers. Groundwater/surface water interactions in streams and aquifers can be complex and the direction of net water flux (into surface water or into the aquifer) may vary spatially along a stream channel and over time at any particular location, depending on the relationship between stream stage and groundwater levels. In some considerations, hydrology
1998-424: The late 1930s and radar satellites at least since 1978. TerraSAR X introduced some technical-industrial novelties. One of these innovations is a kind of zoom shot, with the resolution and scanning field vice versa changeable in a 1:10 relationship, either a larger area to grasp or a small area with the highest possible resolution. Furthermore, the antenna can be aligned by electronics within an angle range so that
2052-403: The maximum rate at which the soil can absorb water, depends on several factors. The layer that is already saturated provides a resistance that is proportional to its thickness, while that plus the depth of water above the soil provides the driving force ( hydraulic head ). Dry soil can allow rapid infiltration by capillary action ; this force diminishes as the soil becomes wet. Compaction reduces
2106-511: The modern science of hydrology include Pierre Perrault , Edme Mariotte and Edmund Halley . By measuring rainfall, runoff, and drainage area, Perrault showed that rainfall was sufficient to account for the flow of the Seine. Mariotte combined velocity and river cross-section measurements to obtain a discharge value, again in the Seine. Halley showed that the evaporation from the Mediterranean Sea
2160-423: The point of view is adjustable. Earlier radar satellites could radiate the antenna only in one direction. With the adjustable angle radar sensor – along with other course refinements ( precession by the earth flattening) – any place on earth can be observed preferentially within 1 to 3 days. For a specific point on the Earth's equator, TerraSAR X has a revisit cycle of 11 days. The revisit time decreases towards
2214-875: The poles, e.g. Northern Europe has a revisit time of typically 3–4 days. The ground operating mechanism and controls for the TerraSAR X is developed by the DLR in Oberpfaffenhofen . It consists of Mission Operating Equipment, the Payload ground segment and the Instrument Operation and Calibration Segment. At the base of the ground segment lies the German Space Operation Center (GSOC), the German Remote Sensing Datum Center (DFD) as well as Institutes for Methodology of Remote Sensing (MF) and
TerraSAR-X - Misplaced Pages Continue
2268-461: The porosity and the pore sizes. Surface cover increases capacity by retarding runoff, reducing compaction and other processes. Higher temperatures reduce viscosity , increasing infiltration. Soil moisture can be measured in various ways; by capacitance probe , time domain reflectometer or tensiometer . Other methods include solute sampling and geophysical methods. Hydrology considers quantifying surface water flow and solute transport, although
2322-412: The radar image represents the radar backscatter for that area on the ground ( terrain return ): brighter areas represent high backscatter, darker areas represents low backscatter. The traditional application of radar is to display the position and motion of typically highly reflective objects (such as aircraft or ships ) by sending out a radiowave signal, and then detecting the direction and delay of
2376-794: The radio waves and can provide data about the objects, including how far the waves traveled and what kind of objects they encountered. Using the acquired data, a computer can create a 3-D or 2-D image of the target. Imaging radar has several advantages. It can operate in the presence of obstacles that obscure the target, and can penetrate ground (sand), water, or walls. Applications include: surface topography & coastal change; land use monitoring, agricultural monitoring, ice patrol, environmental monitoring ;weather radar- storm monitoring, wind shear warning;medical microwave tomography; through wall radar imaging; 3-D measurements, etc. Wall parameter estimation uses Ultra Wide-Band radar systems. The handle M-sequence UWB radar with horn and circular antennas
2430-457: The range direction depends on the pulse width. The resolution in the azimuth direction is identical to the multiplication of beam width and the distance to a target. The AVTIS radar is a 94 GHz real aperture 3D imaging radar. It uses Frequency-Modulated Continuous-Wave modulation and employs a mechanically scanned monostatic with sub-metre range resolution. Laser radar is a remote sensing technology that measures distance by illuminating
2484-490: The reflected signal. Imaging radar on the other hand attempts to form an image of one object (e.g. a landscape) by furthermore registering the intensity of the reflected signal to determine the amount of scattering . The registered electromagnetic scattering is then mapped onto a two-dimensional plane, with points with a higher reflectivity getting assigned usually a brighter color, thus creating an image. Several techniques have evolved to do this. Generally they take advantage of
2538-450: The satellite moves along the day–night boundary of the Earth and allows it to present the same face to the Sun, thus providing the best solar incidence angles to its solar cells for power. TerraSAR-X was designed to carry out its task for five years, independent of weather conditions and illumination, and provides radar images with a resolution of up to 1 m. TerraSAR-X acquires radar data in
2592-551: The target's movement. Monopulse radar 3-D imaging utilizes the ISAR techniques to separate scatterers in the Doppler domain and perform monopulse angle measurement. Monopulse radar 3-D imaging can obtain the 3 views of 3-D objects by using any two of the three parameters obtained from the azimuth difference beam, elevation difference beam and range measurement, which means the views of front, top and side can be azimuth-elevation, azimuth-range and elevation-range, respectively. Monopulse imaging generally adapts to near-range targets, and
2646-437: The time from transmission of a pulse to receiving the echo from a target. Also, range resolution is determined by the transmitted pulse width. The other dimension is called azimuth and is perpendicular to range. The ability of SAR to produce relatively fine azimuth resolution makes it different from other radars. To obtain fine azimuth resolution, a physically large antenna is needed to focus the transmitted and received energy into
2700-451: The time of flight from each transmitting (Tx) antenna to a target and back to each receiving (Rx) antenna, processing data from the numerous ellipsoids formed. The point at which the ellipsoids intersect – known as a hot spot - reveals the exact position of a target at any given moment. Its versatility and reliability make 4D imaging radar ideal for smart home, automotive, retail, security, healthcare and many other environments. The technology
2754-440: The treatment of flows in large rivers is sometimes considered as a distinct topic of hydraulics or hydrodynamics. Surface water flow can include flow both in recognizable river channels and otherwise. Methods for measuring flow once the water has reached a river include the stream gauge (see: discharge ), and tracer techniques. Other topics include chemical transport as part of surface water, sediment transport and erosion. One of
SECTION 50
#17328594619012808-604: The variables constituting the terrestrial water balance, for example surface water storage, soil moisture , precipitation , evapotranspiration , and snow and ice , are measurable using remote sensing at various spatial-temporal resolutions and accuracies. Sources of remote sensing include land-based sensors, airborne sensors and satellite sensors which can capture microwave , thermal and near-infrared data or use lidar , for example. In hydrology, studies of water quality concern organic and inorganic compounds, and both dissolved and sediment material. In addition, water quality
2862-603: Was sufficient to account for the outflow of rivers flowing into the sea. Advances in the 18th century included the Bernoulli piezometer and Bernoulli's equation , by Daniel Bernoulli , and the Pitot tube , by Henri Pitot . The 19th century saw development in groundwater hydrology, including Darcy's law , the Dupuit-Thiem well formula, and Hagen- Poiseuille 's capillary flow equation. Rational analyses began to replace empiricism in
2916-507: Was used for data gathering and supporting the scanning method. 3-D measurements are supplied by amplitude-modulated laser radars—Erim sensor and Perceptron sensor. In terms of speed and reliability for median-range operations, 3-D measurements have superior performance. Current radar imaging techniques rely mainly on synthetic aperture radar (SAR) and inverse synthetic aperture radar (ISAR) imaging. Emerging technology utilizes monopulse radar 3-D imaging. Real aperture radar ( RAR )
#900099