FIG Peer Review Journal


Combined use of spaceborne optical and SAR data – Incompatible data sources, a waste of funds or a useful procedure? (3022)

Charalabos Ioannidis and Dimitra Vassilaki (Greece)
Prof. Charalabos Ioannidis
National Technical University of Athens
9 Iroon Polytechniou St.
Corresponding author Prof. Charalabos Ioannidis (email: cioannid[at], tel.: 00302107722686)

[ abstract ] [ handouts ] [ handouts ]

Published on the web 2008-03-21
Received 2008-01-31 / Accepted 2008-03-14
This paper is one of selection of papers published for the FIG Working Week 2008 in Stockholm, Sweden and has undergone the FIG Peer Review Process.

FIG Working Week 2008
ISBN 978-87-90907-67-9 ISSN 2307-4086


In the recent years there is an increasing interest for high resolution satellite data to be used in a variety of applications, some of which referring to geometric products and mapping using photogrammetric procedures. The recent achievements in acquiring spaceborne optical data with 1m resolution (IKONOS, CartoSAT2, Kompsat-2) or better than 1m in panchromatic images (QuickBird, WorldView-1 and shortly GeoEye-1) has improved the situation. Rigorous models have been developed for orientation and georeferencing of satellite images, regardless the sensor, which gave products (orthoimages, DTM) of accuracies better than 1 pixel. At the same time, the interest on Synthetic Aperture Radar (SAR) sensors and related processing techniques was increased, too. SAR is considered to be unique among the remote sensing systems, as it is all-weather, independent of time of day and able to penetrate into the objects. New SAR sensors can give products of high accuracy, equivalent to optical data. Only last year, 6 SAR systems were launched, TerraSAR-X, Radarsat-2, Sar-lupe II, Sar-lupe III, Cosmo-skymed I, Cosmo-skymed II. It is expected that many more are going to be launched this year. The launched sensors have unprecedented resolution, and they introduce the concept of SAR sensors constellation. SAR and optical data have differences and similarities at the same time. In the past they were considered exclusive, but today they are considered to complement rather than compete with each other. This concept is illustrated with cooperation of optical and SAR satellites, as well as with scientific studies, e.g., about what can be gained when optical and SAR image data used for the interpretation of linear (roads) and man-made (buildings) features. In this paper, the available SAR and optical spaceborne systems are presented, focusing on their properties, the methods for processing them, the applications and the ways in which they can be combined for high quality surveying of earth's surface. Combined use of optical and SAR data can be carried out in sequence, in parallel and auxiliary. When processing data in sequence, the output products of the one set are used as input data for processing the other data set, for fully automated procedures, without using external data (e.g., control points) etc. When processing data in parallel both data sets are independently processed and then the extracted information superimposed for presentation purposes. There are various possible uses, e.g., for coastal zone management where a variety of different kind of information are required and some of them can only be extracted from optical imagery while others can only be extracted from SAR data, and others from both of them. When processing data auxiliary, the products of the one set are treated as complementary information for the products that comes out from the other set. Information that is not possible to be extracted from the one data set or it is extracted incomplete is then extracted/completed by the other set, e.g., improvement of DEM with optical and microwave data fusion.
Keywords: Geoinformation/GI; Remote sensing; Photogrammetry; Optical satellites, SAR