ACCURACY INVESTIGATION OF ORTHOIMAGES 
OBTAINED FROM HIGH RESOLUTION SATELLITE STEREO PAIRS 
L. Zhu *, H. Umakawa, F. Guan, K. Tachibana, H. Shimamura 
Research and Development Center, PASCO Corporation, Annex 2-8-10 Higashiyama, Meguro-ku, Tokyo, 153-0043, 
Japan-(lin_zhu, hirokoumakawa, fang guan, kikuo tachibana, hideki_simamura)@pasco.co.jp 
KEY WORDS: High resolution, Satellite, Geometry, Model, Matching, Orthoimage, Accuracy 
ABSTRACT: 
This study investigates the geometric accuracy of DSMs and orthoimages, which are obtained from high resolution satellite stereo 
pairs of in-track, cross-track and mixed satellite images. Four IKONOS and two QuickBird panchromatic images are used to 
constitute 15 stereo pairs, and are processed to generate DSMs and orthoimages. A geometric stereo model, which represents the 
stereo acquisition geometry of a satellite stereo pair is applied to investigate the relationship between the geometric accuracy of 
DSMs and orthoimages and the parameters of the geometric stereo model. The results showed that the geometric accuracy is mainly 
influenced by two parameters, i.e. base-height ratio (B/H) and bisector elevation (BIE). And, if the stereo acquisition geometry is 
ideal, high accuracy DSMs and orthoimages can also be obtained by cross-track stereo and mixed satellite stereo pairs. 
1. INTRODUCTION 
Spatial information has become indispensable for numerous 
aspects of urban and rural development, planning and 
management, with rapid development in spatial data capture, 
management and access (Kelly, 2007). The increased 
utilization of high resolution satellite imagery has been due to 
recent strides of dramatically improved spatial resolution, wider 
coverage, higher frequency of revisit time especially with 
employment of satellite constellations, as well as considerably 
decreased satellite launch costs. When using high resolution 
satellite imagery for topographic mapping, although in-track 
stereo pair images can ensure the geometric accuracy of 
generated DSMs and orthoimages, as a resource for spatial 
information collection, the limitation such as expensive data 
acquisition fee, paucity of imaging regions and archived data is 
apparent. However, a lot of cross-track images acquired from 
the same satellite or different satellites are available. The full 
exploitation of these images will extend the possibility of 
spatial information collection. Relatively few studies have been 
made regarding the application of high resolution satellite 
cross-track stereo and mixed satellite stereo images. Especially, 
the geometric conditions for accurate DSMs and orthoimages 
generation, and the influence of the stereo acquisition geometry 
have not been clarified. 
In this study, in-track, cross-track and mixed satellite stereo 
combinations of IKONOS and QuickBird images are used to 
generate DSMs and orthoimages. The geometric accuracy of the 
DSMs and orthoimages is assessed. A geometric stereo model, 
which represents the stereo acquisition geometry of a satellite 
stereo pair, is used to investigate the relationship between the 
geometric accuracy of DSMs and orthoimages and the 
geometric parameters of the geometric stereo model. The 
influence the stereo acquisition geometry is analyzed. The 
results show that there is a great potential for using high 
resolution satellite cross-track and mixed satellite stereo images 
for spatial information collection. 
2. DATESETS 
The Hakone region of Japan is chosen as a test field in this 
study. The test field covers both mountain and urban areas. 4 
IKONOS and 2 QuickBird images are used in this study. Table 
1 shows the specification of the used satellite images. The 4 
IKONOS images include 1 in-track stereo pair and 2 single 
images, and all are Geo, 11-bit, lm panchromatic images. The 2 
QuickBird single images are Basic, 11 -bit, 0.65m panchromatic 
images. Since these images are acquired six years apart, from 
2001 to 2006, from different viewing directions, there is a lot of 
difference among them. 15 stereo combinations are constituted 
from the 6 images for DSMs and orthoimages generation, 
including 1 in-track stereo pair, 5 IKONOS cross-track stereo 
pairs, 1 QuickBird cross-track stereo pair, and 8 IKONOS and 
QuickBird mixed stereo pairs. 
Acquisition 
dates 
Spatial 
resolution 
Image ID 
Remarks 
IKONOS 
(Geo) 
2006/4/01 
1.0m 
11 
single 
2003/4/18 
1.0m 
12 
In-track stereo image 
2003/4/18 
1.0m 
13 
In-track stereo image 
2001/4/15 
1.0m 
14 
single 
QuickBird 
(Basic) 
2005/1/14 
0.65m 
Qi 
single 
2006/2/14 
0.65m 
Q2 
single 
Table 1. Specification of used satellite imagery 
22 Ground Control Points (GCPs) are collected within the test 
field and used as check points to evaluate the geometric 
accuracy of generated DSMs and orthoimages. The coordinates 
of the GCPs are measured with a Virtual Reference Station 
(VRS) Global Positioning System (GPS). These GCPs are 
chosen to be distributed over the whole test field which covers 
both mountain and urban areas. 1 GCP is used to remove the 
Corresponding author.