International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B1. Istanbul 2004 
  
In the case of 1:25000 base maps of Iran, in planning phase for 
updating each block (96 sheets at 1:25000 scale), the features of them 
are classified to three main groups: features with rapid change (urban 
areas), features with moderate change (rural areas) and features with 
slow changes (natural areas with little or no cultural development). 
Urban blocks, every 5 years, rural blocks every 10 years and natural 
ones with little or no cultural development every 15 years should be 
revised. Based on this plan, each block must be revised. replying to 
following questions: "will guide our task or suppose revision 
method?" "where changes should be applied?" and "How many 
changes have been occurred?" 
There are alternative ways for map revision. These ways are: ground 
surveying, aerial photogrammetry and space photogrammetry. Map 
revision using remotely sensed data acquired by satellites have 
various advantages comparing to the other methods which 
accessibility, lower costs and regular repeat coverage of the area of 
interest are the most important ones. For image selection, many of 
parameters should be considered, such as: the possibility of providing 
planimetric and altimetric accuracy as well as information content 
with respect to "detection" and "identification" of features. HRG 
mode of SPOTS satellite images with 2.5 meter resolution and its 
geometric characteristics is considered to be suitable for 1:25000 base 
map updating. 
3. OBJECTIVES AND METHODOLOGY 
Objective of this study is to evaluate the potentials of SPOTS HRG 
images and its information content, for extraction ground features in 
the context of updating 1:25000 base map series of Iran and 
associated topographic databases. Since 1:25000 topographic maps 
being typically targeted over the vast sparsely populated areas around 
the world, the results can be used in many developing countries. In 
Figure 2, map revision stages planned for this case have been 
depicted. 
  
  
  
Image selection 
  
  
4 Old topographic maps pu. 
Nr Old maps 
  
  
  
  
  
DEM 
production 
  
  
  
  
  
  
  
  
  
  
  
Test of accuracy 
  
  
  
Field work by GPS 
  
  
  
Superimposing old maps on 
orthorectified image 
  
  
  
Y 
  
Updating of old maps 
  
  
  
Figure 2. map updating stages using HRG ima 
gs 
C 
S. 
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After planning the revision stage, data required for updating process 
including GPS measurements, new satellite images or aerial photos 
must be collected. Then, the collected data is processed to detect and 
revise changes. Finally, updated maps are produced. 
4. TEST SITE AND DATA SETS 
Khouzestan is a boundary province of Iran, and was badly damaged 
during eight years war between Iran and Iraq. Ahvaz (the center of 
province), is located between Longitudes 48°20'and 49° East and 
Latitudes 31°30' and 31? North. It is a flat area with slope lower than 
3%. In figure 3, position of Khouzestan province relative to other 
provinces and digital elevation model (DEM) of Ahvaz city have been 
shown. 
Maps of this city had been produced at the begining of 1:25000 base 
mapping project in 1993. Since those maps are now quite outdated, 
they were selected for this study. 
  
   
Figure 3. DEM and position of Ahvaz relative to other provinces. 
Topographic vector maps at 1:25000 scale in UTM coordinate 
system, DEM with 10 meters resolution, GPS ground control points 
and Ahvaz SPOT 5 HRG image, acquired on 2003, were used as input 
data sets. 
DEM of Ahvaz was produced based on spot heights, contours, water 
lines and water bodies if exist, which have been extracted from 
1:25000 old maps. 
S. PREPARATION STAGES 
For orthorectifying of SPOT imageries, a set of 40 well defined and 
distributed ground control points (GCPs) was collected 
simultaneously on the 1:25000 scale topographic maps and on the 
SPOT HRG image. Figure 4 illustrates spatial distributions of these 
points. 
     
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Figure 4. Distribution of GCPs. 
By applying orbital parameter and using X, Y (extracted from 
planimetric vectors) and Z coordinates (extracted from DEM) of each 
point, Toutin's SPOT model was calculated with 0.93 pixel in RMSE 
   
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