Estimation and Subtraction of Topographic Phase (InSAR operator) | ![]() |
This operator estimates and subtracts topographic phase from the interferogram. More specifically, this operator first radarcodes the Digital Elevation Model (DEM) of the area of interferogram, and then subtracts it from the complex interferogram.
This operator has to be performed after the interferogram generation. It also requires an input DEM, SRTM can be used, or any other DEM supported by NEST. The DEM handling for most of elevation models, selection and download from internet of tiles covering the area of interest, interpolation, accounting for geoid undulation, etc, is performed automatically by the operator itself.
A set of freely available, for the scientific use, digital elevation models are supported by NEST. The elevation models for which tiles are automatically handled by NEST are: SRTM, ACE, and GETASSE. For all others, some administration work is needed. Namely, a manual selection and download of tiles covering the area-of-interest has to be performed; while interpolation and pre-processing of DEM for interefometric applications is also performed automatically by the operator.
Note that interpolation of DEM is conceptually different then in other Geometry NEST operators (eg. Range Doppler Terrain Correction Operator).
The DEM reference phase is computed in two steps:
Source Bands are stack of flat-earth subtracted ("flattened") interferograms.
Output Bands are stack of interferograms with subtracted DEM reference phase and other optional bands, for example: radarcoded elevation of the area, of topographic phase.