The digital height model (DEM) represents the height of the Earth's surface as a height value grid. It serves as necessary tools to understand the topography of earth, hydrology and terrain forms. Scientists, geologists and environmental scientists rely on DEM for various purposes, including terrain analysis, flood modeling and urban planning.
Creating DEMs using open source software such as Pygmtsar (Python Insar) is a perfect example of how modern technology makes complex processes available and fast. After one click, you can start processing and get results for satellite DEM. This example and many other interactive examples of insulation with 3D visualization are available on INSAR.DEV Platform.
The digital facade model is created from radar images obtained by Dane Sentinel-1 in just a few minutes on devices connected to the Internet. This speed and availability make the technology suitable for everyone, without the need for fast internet, large disk space or a powerful computer.
Public radar satellites, such as Sentinel-1, scan our planet during the day and night, intercepting the reflected signal as raster images for later processing. These images store complex values of the reflected signal phase and can be used to obtain various information about the condition and movements of the surface and atmospheric properties of the Earth. The simplest form of processing is to calculate the signal amplitude in order to obtain a image on a gray scale, similar to optical photography, but regardless of the time of day and cloud protection.
The true potential of radar satellites is revealed during the processing of complex data. The length of the Sentinel-1 radar wave is 56 mm, which allows the registration of precise heights and displacements of the Earth's surface at the order of the millimeter fraction. If the surface subsides for a millimeter, the radar beam moves an additional distance of 1 millimeter to the surface and back, a total of 2 millimeters. This slight delay can be registered and processed.
In addition to surface displacement, the images contain a so -called atmospheric phase, which is a signal delay when it passes through the atmosphere. In cases of severe atmospheric turbulence or cloud covering, the delay of the atmospheric phase may match hundreds of millimeters of surface displacement. Therefore, it is necessary to precisely separate different sources of signal change to achieve monitoring of high -accuracy surfaces.
In the case of such precise calculations, the satellite orbit should be thoroughly known and orbit errors. Solid earthworms caused by the moon and sun also affect data that can be compensated analytically or based on the given spatial spectrum.
For illustrative and educational purposes, a pair of “perfect” images is chosen from a well -repeated rocky area with a low cloud cover. In industrial use, various methods of processing the image series are used. In the case of DEM construction, the accuracy of the sub-millimeter is not required, so in the case of a well-chosen area, data analysis is performed automatically without selecting parameters. When vegetation and cloud cover are present, additional operations are needed to separate these signal components and assess the accuracy of the results.
Sentinel-1, the only global publicly available satellite, is currently in orbit. Almost a decade of photos is available, which allows us to build detailed topography and study surface displacement, infrastructure, earthquake effects and many other processes and phenomena on our planet. Two new Sentinel-1 and pond radar satellites Nisar satellite From NASA and Indian Space Research, the organization (ISRO) is to be launched by the end of the year.
