Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa, 2014, Vol. 11, No. 2, pp. 228-240
Difference between radar and radiometric signatures (the case of eutrophic lake ice cover)
G.S. Bordonskiy
1 , A.A. Gurulev
1 , A.O. Orlov
1 , S.V. Tsyrenzhapov
1
1 Institute of Natural Resources, Ecology and Cryology SB RAS, Chita, Russia
The problems of connection between passive (radiometric) microwave and active (radar) measurements are discussed in the paper. Taking ice cover of fresh eutrophic lake as an example, radar and radiometric measurements were shown to reveal different signatures in it. The research was done using the results of satellite, airplane and car installed equipment in the process of measuring in centimeter band. At the same time, structural features of ice cover containing trapped organic matter (plankton, higher aquatic vegetation) and gas inclusions, ice mineralization and other parameters were studied.
It was determined that increments of signals in the process of radar and radiometric measuring can give different information on the ice cover structure. The main differences between the patterns of active and passive remote sensing are related to the following features: 1 – emissivity determining the values of radio brightness temperature is more sensitive to the object state on the media borders comparing to back-scattering coefficient; 2 – anisotropy of probing conditions due to differences in background temperatures (using radiometry) and preferential direction of artificial emission (using active probing) enable differences in signal variations; 3 – non-isothermality of real media makes radio brightness contrasts; 4 – some difference between the spectrum signals in two probing techniques results in changing interference properties of registered emissions.
Therefore, existing point of view on radar and radiometric image as “a negative” and “a positive” requires some refinement for a definite class of objects. Development of microwave radiometric systems with higher spatial resolution comparable with SAR would be appropriate.
Keywords: radar image, active and passive radiolocation, ice cover, eutrophic water body
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