International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B7. Istanbul 2004 
carries a state-of-the-art sensor and is the most advanced 
commercial imaging system in orbit. 
One of the pictures of this satellite belonging to our project 
area is shown in Fig. 2. 
      
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Figure 2. image in Riyadh 
2.3 Ground Control Points (GCPs) 
In the orthorectification of HRS images, GCPs play very 
significant role. For IKONOS and QuickBird images, GCPs 
were established to dm-level accuracy at a spacing of about 5 
km. In case of LANDSAT-7 images, GCPs were established 
to m-level accuracy at a spacing of about 50 km. 
In order to establish GCP archive to be used in future, for 
each GCP, a description card was prepared and in many 
cases photos were also taken at these points from a short and 
medium range. The coordinates of GCPs were determined in 
the national datum (Shedayed et al., 1992) as well as the 
WGS84 datum. 
2.4 Digital Elevation Models (DEMs) 
It is to be noted that the IKONOS Geo product and 
QuickBird Basic and Standard Ortho Ready Imagery Data 
requires to be processed with the refined Image Support 
Data (ISD) set, including the orbital parameters of the sensor, 
GCPs and a Digital Elevation Model (DEM), to obtain the 
[mage accuracy at the level of 1.0 — 1.5 pixels. 
The accuracy and resolution of the DEM required for the 
orthorectification of the Satellite Images is depending on the 
[mage georeference position accuracy specified by the 
Customer. Since it is aimed to have 1.0 — 1.5 pixel accuracy 
in our projects, a DEM with an accuracy of at least 5 meters 
is required. 
2.5 Orthorectification 
The system corrected satellite images are subject to errors 
and distortions due to height differences and lack of precise 
ground control points. These errors may be as big as 50 
meters in case of the system corrected HRS images 
depending on the magnitude of vertical angle and 
topographic relief. As part of this project, the 
orthorectification of IKONOS and QuickBird images to 1.0 — 
1.5 pixels was performed very successfully. The 
orthorectification process was carried out using Russian 
OrthoSpace, which uses a dynamic model without requiring 
sensor camera parameters and / or PCI with sensor 
parameters and rational polynomial coefficients. The 
mosaicking was carried out using IRAS-C software. 
3. SAUDI GEODATABASE USING HRS 
IMAGES AND PLANS 
3.1 Image Geodatabase 
Using HRS images, a very comprehensive geodatabase was 
established. It consists of about 
100,000 km? of IKONOS and QuickBird images (Fig. 3) 
2,000,000 km” of LANDSAT-7 images (Fig. 4) 
structural plans of the entire Saudi Arabia 
- local plans and subdivisions of Qaseem, Riyadh and 
Aseer regions (Fig. 5) 
  
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