The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B4. Beijing 2008 
1312 
• The step of image processing isn’t time consuming 
• The large covered area with each satellite image will 
cause the elimination of block adjustment and mosaic 
production 
• Needing to less control point and having orbital 
information that can be used as exterior orientation 
parameter or primary values 
• With access to high resolution satellite images, these 
images can be replaced or complemented for aerial 
images for mapping 
• The facility of obtaining stereo images with using 
tilted mirror 
Of course beside these advantages, satellite images also have 
some defects; 
• Receiving stereo images with regards to problems 
such as existence of clouds or snow and sometime 
overlapped image are related to different season that 
cause problems in 3D model production and object 
extraction 
• Resolution of satellite images and their information 
contents are less than resolution of large scale aerial 
images and their information contents 
The second problem maybe is most problematic issue in 
satellite imagery. This cause satellite images not to be replaced 
by aerial images but used as complement for aerial images. 
Although, it is maybe possible to ignore this problem because 
of the capability of receiving repetitious and periodic satellite 
images, fast image processing, large covered area with each 
satellite image and the advantages of access to far and restricted 
areas (Holland and Marshal, 2006). With regard to the 
advantages of satellite images and also access to the IRS-P5 
stereo images, in this paper, geometric accuracy and 
information contents of these images related to the objects 
containing in 1:25000 scale maps are evaluated. 
2. IRS-P5 STEREO IMAGES FOR REVISION OF MAPS 
AT 1:25000 
2.1. IRS_P5 mission 
IRS-P5 is a spacecraft of ISRO (Indian Space Research 
Organization), Bangalore, India. The objectives of the IRS-P5 
mission are directed at geo-engineering (mapping) applications, 
calling for high-resolution panchromatic imagery with high 
pointing accuracies. The spacecraft features two high-resolution 
panchromatic cameras that may be used for in-flight stereo 
imaging. Hence, IRS-P5 is also referred to as CartoSat-1. In this 
mission, the high resolution of the data (2.5 GSD) is being 
traded at the expense of multispectral capability and smaller 
area coverage, with swath width of 30 km. The data products 
are intended to be used in DTM (Digital Terrain Model)/DEM 
(Digital Elevation Model) generation in such applications as 
cadastral mapping and updating, land use as well as other GIS 
applications. PAN-F (Panchromatic Forward-pointing Camera), 
featuring a fixed forward tilt of 26*PAN-(Panchromatic Aft- 
pointing Camera), it is fixed at an aft tilt of -5*. Each camera 
provides spectral range of 0.5 - 0.85 pm, a spatial resolution of 
2.5 m, a swath width of 30 km, and data quantization of 10 bits. 
Stereo imagery is acquired with a small time difference (about 
50 s) due the forward and backward look angles of the two 
cameras. The major change in imaging conditions during this 
time period is due to rotation of Earth. An algorithm for Earth 
rotation compensation is being used to eliminate the delayed 
observations of the two cameras (1RS user's Hand book). 
2.2. The project of 1:25000 scale maps production 
The primary study of the project of 1:25000 scale maps 
production started in 1987. Production of these maps started in 
1991 and National Cartography Center could produce % 90 of 
these maps until July 2007. As mentioned before, because of 
flying problems other of areas related to frontiers. 
Contour 
Interval 
Accuracy 
Accuracy 
Resolution 
in height 
0.3xC.I. 
Planimetrie 
(in 0.3 mm) 
Planimetrie 
(in 0.1 mm) 
10m 
3 m 
7.5 m 
2.5 m 
Table 1. Features of 1:25000 scale maps 
3. PRACTICAL EVALUATION 
3.1 The area of case study 
For IRS P5 stereo images evaluation, the stereo images of 
Shiraz are selected. For geometric accuracy evaluation, 113 full 
points are extracted from 1:2000 scale maps. With regard to the 
geometric accuracy of 1:2000 scale maps, it is necessary to 
mention that geometric accuracy of the full points is better than 
60 cm (contour interval of 1:2000 scale maps is 2 meter). 
In header file of IRS P5 stereo images, we have 90 RPC 
(Rational Polynomial Coefficients) that these RPC calculated 
based on time and position of imagery (ERDAS IMAGINE 9.1 
Online documentation). By using these RPC, geometric 
correction without any control points is possible. But by using a 
number of control points, we find out significant improvement 
in result. Access to these RPC in ERDAS IMAGINE 9.1 is 
possible that we used this software for evaluation of 1RS P5 
stereo images geometric correction. We used Geomatica V8.1 
for geometric correction evaluation by using polynomial 
equations and rational functions model without using RPC. 
Figure 2. Distribution of control and check point in IRS_p5 
image of Shiraz 
3.2 The mathematical models using in this investigation 
A rational function model and a 2D Polynomial equation model 
applied on the images used in this project. Brief descriptions of 
these models are given in the followings: