Abstract
Global navigation satellite system (GNSS)-based synthetic aperture radar interferometry (InSAR) employs GNSS satellites as transmitters of opportunity and a fixed receiver with two channels, i.e., direct wave and echo, on the ground. The repeat-pass concept is adopted in GNSS-based InSAR to retrieve the deformation of the target area, and it has inherited advantages from the GNSS system, such as a short repeat-pass period and multi-angle retrieval. However, several interferometric phase errors, such as inter-channel and atmospheric errors, are introduced into GNSS-based InSAR, which seriously decreases the accuracy of the retrieved deformation. In this paper, a deformation retrieval algorithm is presented to assess the compensation of the interferometric phase errors in GNSS-based InSAR. Firstly, the topological phase error was eliminated based on accurate digital elevation model (DEM) information from a light detection and ranging (lidar) system. Secondly, the inter-channel phase error was compensated, using direct wave in the echo channel, i.e., a back lobe signal. Finally, by modeling the atmospheric phase, the residual atmospheric phase error was compensated for. This is the first realization of the deformation detection of urban scenes using a GNSS-based system, and the results suggest the effectiveness of the phase error compensation algorithm.
Highlights
Global navigation satellite system (GNSS)-based synthetic aperture radar (SAR) employs GNSS satellites as opportunity transmitters, and the receivers can be stationary or mounted on a vehicle or aircraft [1,2]
For SAR interferometry (InSAR), the existing research is about combining InSAR data with GNSS ranging data [3,4,5]
For GNSS-based systems, the signal-to-noise ratio (SNR) is low, so directly compensating for the atmospheric phase error through parameter estimation will introduce a deviation in the accuracy [33]
Summary
Global navigation satellite system (GNSS)-based synthetic aperture radar (SAR) employs GNSS satellites as opportunity transmitters, and the receivers can be stationary or mounted on a vehicle or aircraft [1,2]. The space baseline of repeat-pass in GNSS-based InSAR is much larger than that of the traditional system since the GNSS satellites are not dedicated SAR transmitters In this case, the derived phase error is very large since uncertainty in the elevation error of the imaging area is inevitable. For GNSS-based systems, the signal-to-noise ratio (SNR) is low, so directly compensating for the atmospheric phase error through parameter estimation will introduce a deviation in the accuracy [33]. The second is that the transmission power of the GNSS is low, so the SNR of the image is low [33] Both the factors mean that the traditional error compensation algorithms for ground-based SAR and low Earth orbit (LEO) SAR would introduce a large deviation in GNSS-based system. The experiment proved the deformation retrieval capability of the GNSS-based system in urban areas, which provides a basis for the subsequent deformation retrieval experiment of natural scenes
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