993
OPTICAL/SAR SENSORS STEREO POSITIONING
Shuai Xing*, Qing Xu, Yan Zhang, Yu He, Guowang Jin
Zhengzhou Institute of Surveying and Mapping, 450052 Zhengzhou, China - xing972403@163.com
Commission I, ICWG I/V
KEY WORDS: Accuracy, Mapping, Orientation, Optical, Photogrammetry, Stereoscopic, SAR
ABSTRACT:
Up till now it is still difficult to acquire stereoscopic space-bome image pairs of some area due to climate condition or atmosphere
pollution. This paper describes the geometric aspects and the mathematical treatment for the stereoscopic image pair composed of
optical and SAR space-bome images in positioning. First, the geometric equation for linear array push-broom imagery and F. Leberl
model for SAR imagery as well as methods to simultaneously determine or refine individual parameters of these models are briefly
reviewed. And a straight-forward single-step procedure has been developed which follows the philosophy of photogrammetric bundle
adjustment techniques. Secondly, from these imaging models of one optical and SAR image, the composite stereoscopic pair is
constructed. The stereo positioning is the process of determining the ground coordinate of a ground point from a pair of homologue
points in the composite stereoscopic pair. Experimental results show that it is feasible to construct stereoscopic pair with one optical
and SAR image, of which the average positioning RMS value is close to stereoscopic pair with optical/optical or SAR/SAR images.
1. INTRODUCTION
High resolution optical stereoscopic image pairs achieved by
some commercial remote sensing satellites, such as IKONOS,
SPOT5, Quickbird etc, have been widely used to produce
medium and large scale cartography. But until now it is difficult
to acquire satisfied optical space-bome image of some area, like
basin or tableland, for complicated climate or serious
atmosphere pollution. Radargrammetry is a good solution to
this problem, but the stereoscopic observation and interpretation
of SAR stereoscopic image pair are extremely rigorous. So this
paper describes another solution as Figure 1, which constructs a
stereoscopic pair with optical/SAR space-bome images for
stereo positioning.
Figure 1. Scheme of a multi-sensor stereo positioning
After Moore first proposed the stereoplotting based on the
stereoscopic pair with SAR and optical images in 1970, lots of
works on theory have been done in the past twenty years. In
1990 Johannes Raggam and Alexander Aimer (Raggam
Johannes et al., 1990) of institute for image processing and
computer graphics in Austria have analyzed the geometric
aspects and the mathematical treatment of stereoscopic pair
composed of optical and SAR space-bome images, and have
chosen a Seasat SAR image, SPOT image and Landsat TM
image to construct three stereoscopic pairs. Accuracies of stereo
positioning are that planimetrie error is 28-45m and altimetric
error is 14-30m. In the middle of 1990s, two satellites, ERS-1
and Radarsat-1, have been launched successfully and high
resolution SAR images could be acquired. And the high
accuracy of composite positioning has been achieved too. In
1993 Renouard and Perlant (Renouard L., 1993) combined
SPOT and ERS image to achieve planimetrie error 15m and
altimetric 10m. In 1994 Toutin chose Radarsat, RSO-C/X, ERS,
SPOT and Landsat TM images, and stated planimetrie errors
around 15m and altimetric around 20m. In 2004 Alain Giros of
ESA tried to auto register and composite position SPOT and
ERS-2 images to achieve planimetrie error 10-40m and
altimetric 10-17m. (Jordi Inglada et al., 2004; Alain Giros,
2005) In 2006 Fang Yong et al. (Fang Yong et al., 2006) tried
to stereoplotting with Radarsat-1 and ERS-2 stereoscopic pair
based on G. Konecny model and achieved planimetrie error
34.24m and altimetric 14.08m.
In this paper the stereoscopic pair composed of linear array
push-broom and SAR space-bome images is discussed, its
construction and procedure of stereo positioning are described
in details. First the imaging models for linear array push-broom
imagery and SAR imagery are introduced in section 2. Then the
mathematical treatment of composite stereoscopic pair is
constructed in section 3. Section 4 shows experimental results
with six stereoscopic pairs and section 5 shows conclusions.
2. TWO IMAGING MODELS
2.1 The Scanning Model
The linear array push-broom imagery is acquired with linear
sensors by scanning the Earth surface. The relationship between
ground and image is rigorous central projection. Each line of
the image has different elements of exterior orientation. The
collinearity equation of i line is expressed in the following
way: (Qian Zengbo et al.,1992; Chang Benyi, 1989; Yan Qin et
al., 2001)