SAR imagery (Radar satellite data)

Purposes and Objectives of SAR imagery/SAR images (Radar satellite data)

The purpose of space radar imaging is to obtain timely and relevant information about the terrain and water surface, which is necessary for solving numerous tasks in various fields of activity. The main objectives of radar imaging include:

• Creation and updating of topographic maps and plans, as well as other cartographic products;
• Creation of engineering-geological maps for geological surveys;
• Land management and cadastral work;
• Generation of digital terrain models for planning and development of telecommunication networks;
• Agricultural research, detection of plant diseases, determination of vegetation phase;
• Monitoring of emergencies and their consequences, control of emergency restoration work;
• Forest inventory (forest assessment, determination of age, height, and diameter of growing trees, wood reserves, annual growth, etc.);
• Detection of oil spills;
• Detection of fuel dumping from ships;
• Information support for the prevention and elimination of oil and petroleum product spills;
• Monitoring of deformation and displacement of the Earth's surface in mining areas;
• Monitoring of structural deformations in urban areas;
• Monitoring of critical industrial facilities;
• Pipeline monitoring;
• Monitoring of roads and railways and other objects;
• Monitoring of ice conditions and ship movements;
• Monitoring of natural and man-made hazardous processes, including earthquakes, landslides, avalanches, sinkholes, flooding, karst, suffusion, river erosion, coastal erosion, and changes in sea and reservoir coastlines.

Initially, the tasks of radar imaging were limited to the study of the ocean surface. However, the scope of radar imaging has expanded, and it now allows for obtaining data on millimeter-level displacements of objects on the Earth's surface, tracking oil pollution and maritime situations in water areas, as well as creating digital terrain models (the well-known SRTM DTM is based on radar data processing).

Advantages of Radar Imaging/SAR Images

Radar imaging offers several advantages compared to other observation methods. It provides high precision in measuring the coordinates and geometric characteristics of objects and the ability to obtain radar images at any time of day and in any weather conditions (microwave radiation easily penetrates through clouds and does not rely on daylight, unlike visible and infrared imagery).

• Ability to conduct radar imaging in any weather conditions (including strong cloud cover) and at any time of day (including nighttime);
• High level of detail due to the high spatial resolution of radar imagery;
• Cost-effective alternative to GPS monitoring of ground displacements.

Innovative processing techniques open up new areas of radar imaging utilization, including:

• The ability to conduct radar imaging regardless of weather conditions makes it particularly valuable for mapping remote regions in the Far East of Russia and other countries, where snow hinders imaging during the winter and continuous cloud cover occurs during the rainy season throughout the imaging season. Another advantage of radar imaging for cartography is its relatively high spatial resolution, which enables the creation and updating of maps up to a scale of 1:50,000.
• By using the phase information of radar signals, digital elevation models and terrain models can be created through interferometric processing. These models can be used in various areas of society.
• Temporal radar images provide information on ground surface displacements. This helps detect ground subsidence in mining areas, deviations of infrastructure objects from their normal positions, and track landslide processes.
• SAR images of water surfaces enables the detection of oil spills. Due to the specific characteristics of oil, which result in a smoother surface and different reflectivity compared to natural water, oil spills can be easily identified on radar images.
• SAR images allows for the detection of ships that have intentionally disabled their tracking signals or have lost signal due to accidents. Radar signals are well reflected by metallic surfaces, enabling the automatic detection of ships even on medium-resolution radar images. Moreover, radar images can be obtained just an hour after acquisition, providing more precise information to the relevant authorities.
• The varying reflectivity of radar imaging allows for the detection of forest fires and deforestation in forest areas, as well as monitoring the condition of agricultural crops.