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The Multi-Chromatic Analysis (MCA) uses interferometric pairs of SAR images processed at range sub-bands located at
different spectrum positions, and explores the phase trend of each pixel in the frequency domain. The phase of stable
scatterers evolves linearly with the sub-band central wavelength, the slope being proportional to the absolute optical path difference. Consequently, both phase uwrapping and height computation can be performed on a pixel by pixel basis without spatial integration. Recently the technique has been used to derive ground elevation by processing
interferometric pairs acquired in Spotlight mode by both TerraSAR-X and COSMO-SkyMed satellite missions. However, further potential applications are possible. In particular, this work is aimed at experimenting the use of MCA for measuring the optical path between the SAR sensor and the scene by processing a single SAR acquisition. In this configuration, the slope of the phase trend along frequencies depends on the full optical path. In order avoid liasing, we adopted a processing scheme which consists in subtracting from the SAR image phase a term proportional to the distance computed through inverse geocoding. Assuming negligible the positioning errors, the validation of this approach can be performed by comparing the distance measured by MCA with the atmospheric delay computed through analytical models. We carried out a feasibility study aimed at evaluating the maximum value for the errors in satellite and target positions, allowed to perform the reliable validation. Then, in order to reduce the error in the target positions and to guarantee good phase stability, we selected SAR acquisitions which include artificial corner reflectors to be used for MCA processing and the following validation procedure. We present results obtained by exploiting two corner reflectors visible within two TerraSAR-X images acquired in Spotlight mode over Venice Lagoon.
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