In: Wagner W., Székely, B. (eds.): ISPRS TC VII Symposium - 100 Years ISPRS, Vienna, Austria, July 5-7, 2010, IAPRS, Vol. XXXVIII, Part 7B 
SAR STEREO-MAPPING BASED ON DEM 
Shucheng Yang a ’ b , Guoman Huang b , Zheng Zhao b 
a School of Geodesy and Geomatics, Wuhan University, Wuhan, Hubei, P.R.China - yangshucheng2003200I@yahoo.com.cn 
b Chinese Academic of Surveying and Mapping, No. 16 Beitaiping Road, Haidian District, 
100039, Beijing, P.R.China - huang.guoman@163.com;zhengzhaochina@163.com 
KEY WORDS: SAR image, stereo-mapping, parallax, DEM, stereoscopic image pair, topographic map; 
ABSTRACT: 
In the western region of China, Synthetic Aperture Radar images have been used in extraction of topographic maps. Stero mapping 
with stereoscopic image pair is very useful for extraction of feature elements (roads, buildings and other surface features) from SAR 
image. The basis of stereo-mapping is stereoscopic image pair, of which the vertical parallax must be removed, and the horizontal 
parallax reserved. This paper presents a method of generating SAR stereoscopic image pair based on Digital Elevation Model, which 
is used in stereo-mapping. First of all, orientation of SAR image must be completed; then according to DEM, stereoscopic image can 
be generated through image re-sampling along the range direction from original image. The vertical parallax will be removed, when 
re-sampling, and the horizontal parallax will be reconstructed with central projection or slant-range projection. There are two ways to 
generate stereoscopic images from single original image or two different original images. The two images generated from single 
original image are called mono-source pair. The two images generated from the two different images are called dual-source pair. 
Experiment is done in this paper with high-resolution space-borne SAR images. Mono-source and dual-source stereoscopic image 
pairs are generated with central and slant-range projection, and feature elements of topographic map are extracted with the image 
pairs in the experiment. It proves that the method above is feasible. 
1. INTRODUCTION 
SAR is an active microwave imaging system with high 
resolution. Compared with optical sensors, it has series of 
advantages, such as all-day, all-weather and penetrating through 
cloud, mist and a certain depth of ground, and so has been used 
in many fields. As the development of SAR technology, its 
applications are expanding continuously. The technologies, 
generating ortho-image with SAR image, extracting three- 
dimensional topographic information with InSAR and 
deformation monitoring with D-InSAR (M.Gelautz, 2004), have 
been relatively mature, but research on SAR analytical stereo 
mapping is still limited. The key technique of stereo-mapping is 
generation of ideal stereoscopic image pair, of which the 
vertical parallax must be eliminated, and the horizontal parallax 
reserved (Franz.W.Leberl, 1985). Because of existence of 
epipolar line, ideal stereoscopic image pair can be made with 
optical stereo image pair re-sampling along the epipolar line 
and eliminating the vertical parallax between the left and right 
images (Z.X. Zhang, 1997). The method of this paper is re 
sampling along the same geographic direction with SAR images 
to eliminate the vertical parallax and reconstruct the horizontal 
parallax according to DEM. The mono-source stereoscopic 
image pair has well stereoscopic vision, and can be used to 
assistant image interpretation. The dual-source stereoscopic 
image pair has more detailed topographic information, and can 
be used to map and edit contours. The principle and method of 
mono-source and dual-source will be introduced, and the 
experiment with SAR image will be done. 
2. GENERATION OF IMAGE PAIR 
In the method of this paper, the two images of stereoscopic 
image pair can be re-sampled from single SAR image, and also 
can be from two different SAR images with overlapping regions. 
The specific approach is extracting the relatively independent 
stereoscopic image firstly, and then making up a stereoscopic 
image pair with two stereoscopic images. 
The procedure of extracting stereoscopic image is actually a 
process of image simulation. Establish the map between the 
simulated image and the original SAR image with simulated 
imaging orbit and imaging parameters (resolution), and then 
resample to get stereoscopic image. The image re-sampling 
depends on DEM in the same direction, so two maps should be 
established. One is the map between original image coordinates 
and geographic coordinates, the other is between geographic 
coordinates and simulated image coordinates. In this way, the 
vertical parallax will be eliminated, and the map between the 
original image coordinates and simulated image coordinates is 
established indirectly. 
2.1 SAR Image Geometry 
Establishing the map original image coordinates and geographic 
coordinates is geo-location of SAR image, the key is the 
establishment of SAR Geo-location model. SAR Geo-location 
model is the basis of SAR image geometric process, several 
models have been raised at home and abroad at present. Among 
them, the Range and Duppler (R-D) model follows SAR 
imaging geometry strictly, so it can be used for the basic model 
of SAR image geometric process (E.X.Chen, 2004). With an 
SAR image, the formulation of R-D model is as follows: 
r=K-k\ 
' , = 2 (A-ffJU <» 
" * K-A| 
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