Radar survey and its derivative products are gaining popularity. This is easily explained by the features of this type of Earth survey: neither the weather nor the time of day practically affect the image quality.

Radar survey (RS) is a type of space survey in which the microwave radiation range with wavelengths from 1 cm to 1 m is used to obtain information. RS is an active method of remote sensing of the Earth. The satellites are equipped with synthesized aperture radar (SAR), which allows you to take images.

The first radar tests were conducted in the United States and the USSR in the 1960s to search for vessels in high latitudes and other military targets. In 1968, in the USSR, The laboratory of aerometods of the Ministry of Geology of the USSR began the first tests of area radar aerial photography for the needs of Geology. The tests used Soviet side-view radar systems "Toros" and “NIT". The first radar survey from space with a resolution of 25 m was made in 1978 from the SeaSAT satellite. And in 1981, images with a spatial resolution of 40 m were taken by the Space Shuttle. Active use of radar imagery began in 1991 with the launch of the ERS – 1 satellite with radar. Initially, the purpose of using the first civilian radar satellite with an average spatial resolution (20 m) was limited to monitoring the seas. However, after the satellite has completed several complete cycles around the Earth, it turned out that in addition to marine applications, this satellite has a great potential for solving various tasks on land.

Table 1. The most common ranges of radar survey

Range

Frequency, GHz

Wavelength, cm

Satellite systems

X

5,2–10,9

2,75–5,77

(2,4–3,8)

Asnaro-2

TerraSAR-X/TanDEM-X

Cosmo-SkyMed 1-4

Iceye

C

3,9–6,2

3,8–7,6

Sentinel-1

RADARSAT-1

RADARSAT-2

Kompsat-5

GaoFen-3

L

0,39–1,55

19,3–76,9

(15–30)

SIR-A,B

JERS

ALOS PALSAR

The principle of operation of a radar satellite: the spacecraft sends a radar signal in the microwave range, which reaches the earth's surface and reflects off it, as well as partially penetrates inside. The radio signal can penetrate deep to a distance equal to half the wavelength. The intensity of the reflected signal is determined by the surface properties (roughness, humidity, orientation in space, slope steepness, permittivity, etc.) and the radiation wavelength, so different shooting ranges are suitable for different tasks (Fig. 1). After that, the reflected signal is returned to the satellite andregistered.

Radar survey has many applications in various fields: forestry and agriculture, oceanography, urban planning, transport structure, and especially in the extractive industry, including the oil and gas industry.

Application of radar survey in the oil and gas industry:

1.     Creation and updating of topographic maps of various scales, inventory of objects in mining areas and protected areas. This is especially true for regions with prolonged cloud cover, such as the Far East.

2.     Monitoring of oil spills in marine areas. An oil spill is a thin film that differs in texture and structure from water. On radar images oil spills are different:

  • a regular and simple geometric shape;
  • smoothed borders with a slightly higher gradient than the cover of natural origin;
  • small size (large spots are usually coatings of natural origin, such as accumulations of algae or plankton).

Monitoring of oil spills is important not only for oil production sites, but also for oil loading ports and water areas where the routes of oil tankers run. Some ships dump fuel waste on the approaches to the port, so as not to pay for the disposal and recycling of spent fuel. Also, radar data can detect vessels that do not have a tracking signal.

3.     Analysis of the terrain. The radar survey actually scans the territory, and a digital model of the terrain and terrain can be created based on the data obtained.

4.     Monitoring of the earth's surface displacements using interferometric processing of radar surveys. Interferometric measurements are performed using pairs of images of the same territory obtained at different sensor positions and in different time periods. To form such pairs, a cycle of repeated overflight over the territory is used. SSC data is required to obtain information about the intensity and phase of radiation. The offset values are determined by calculating the difference between the reflection points on the image. The offset values are determined by calculating the difference between the reflection points on the image. The measurement accuracy may be less than a millimeter. Interferometric methods (INSAR-Interferometric Synthetic Aperture Radar) can only be used if the paired images are very similar.

Pipelines for transporting oil and gas often run in places where the earth's surface is likely to shift: karst, slope, and so on. Interferometric processing of radar images allows you to avoid a disaster when the earth's surface changes significantly. The frequent repetition of shooting (on average every 7-11 days) and a large frame area allow monitoring on a regular basis.

Radar interferometry is also applicable in other areas of human activity:

  • In urban planning, radar interferometry can be used to determine the level of displacement of buildings and slopes.
  • The mining industry is constantly monitoring the condition of the area to avoid dangerous situations. In places of mining, land surface subsidence often occurs due to the formation of voids inside.

An important task now is to automate the process of conducting interferometric analysis, so that when a new radar image is received, the program can automatically analyze the offsets relative to the previous position of points, and could itself signal the need to take recautions. Deep training in interferometric processing of radar satellite images has not yet been applied anywhere in the world, and Innoter is a pioneer in this direction.

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