Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa, 2019, Vol. 16, No. 2, pp. 45-50
Dependence of the noise level estimates supplied with TerraSAR-X data on the used preprocessor version
D.V. Ivonin
1 , A.Yu. Ivanov
1 1 P.P. Shirshov Institute of Oceanology RAS, Moscow, Russia
Accepted: 13.02.2019
DOI: 10.21046/2070-7401-2019-16-2-45-50
The paper draws the attention of specialists dealing with TerraSAR-X synthetic aperture radar data to a problem of correct calculation of the instrument noise floor (the noise equivalent sigma zero, NESZ) in older versions of the data. The NESZ is a critical parameter when using polarization methods of processing radar data in areas with a reduced level of scattered signal at sea (oil and biogenic films, wind shadow and gradient flow zones, etc). Depending on weather conditions, incidence angle and presence of oil films on the sea surface, the level of the backscattered signal to the radar can vary from –30 to –10 dB. The level of NESZ for the TerraSAR-X can vary from –20 to –28 dB. Thus, the NESZ signal-to-noise ratio for the TerraSAR-X sensing conditions may be significantly lower than 0 dB, for which it is necessary to reject highly noisy data in order not to get the results of incorrect processing at the output. However, as it was discovered that, depending on the processing time and version of the preprocessor, there is a strong variation of up to 4 dB in the NESZ level estimates supplied with the radar data in xml format. This fact was revealed in the course of comparing data obtained at the same time for the same ocean area, but taken from different databases. This paper analyzes the identified inconsistencies in identical data; as well as errors in TerraSAR-X polarization data processing that were obtained earlier due to these problems with NESZ.
Keywords: TerraSAR-X, noise level, NESZ, sea surface, polarimetric methods
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