RADARGRAMMETRIC DIGITAL SURFACE MODELS GENERATION FROM TERRASAR-X IMAGERY: CASE STUDIES, PROBLEMS AND POTENTIALITIES
Other literature type
(issn: 2194-9034, eissn: 2194-9034)
The interest for the radargrammetric approach to Digital Surface Models (DSMs) generation has been growing in last years thanks to
the availability of very high resolution imagery acquired by new SAR (Synthetic Aperture Radar) sensors, as COSMO-SkyMed,
Radarsat-2 and TerraSAR-X, which are able to supply imagery up to 1 m ground resolution.
DSMs radargrammetric generation approach consists of two basic steps, as for the standard photogrammetry applied to optical
imagery: the imagery (at least a stereo pair) orientation and the image matching for the generation of the points cloud. The steps of
the radargrammetric DSMs generation have been implemented into SISAR (Software per Immagini Satellitari ad Alta Risoluzione),
a scientific software developed at Geodesy and Geomatics Institute of the University of Rome “La Sapienza”.
Moreover, starting from the radargrammetric orientation model, a tool for the Rational Polynomial Coefficients (RPCs) for SAR
images have been implemented. The possibility to generate RPCs, re-parametrizing a rigorous orientation model through a
standardized set of coefficients which can be managed by a Rational Polynomial Coefficients (RPFs) model (similarly to optical
high resolution imagery) sounds of particular interest since, at present, the most part of SAR imagery (except from Radarsat-2) is not
supplied with RPCs, although the corresponding RPFs model is available in several commercial software. In particular the RPCs
model has been used in the matching process and in the stereo restitution for the DSMs generation, with the advantage of shorter
This paper discusses the application and the results of the implemented algorithm for radargrammetric DSMs generation from
TerraSAR-X SpotLight imagery, acquired in Spotlight mode over Trento (Northern Italy). Urban and extra-urban (forested,
cultivated) areas were considered in two different tiles, and a final overall accuracy ranging from 4.5 to 6 meters was achieved as
regards the point clouds, enough well distributed independently from the land cover; moreover, it was highlighted the benefit to filter
the originally derived points cloud with a global DSM as SRTM DEM, what leads to an accuracy improvement of about 20% paying
a loss of matched points of about 10 %.