The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
Figure 3. Ortho-image for the study area 
Effect of DEM Resolution / Accuracy on Ortho Image 
Generation 
Ortho image was generated at 2.5 m by using DEM at different 
resolutions. The effect of resolution on ortho image generation 
is studied at different pixel resolution belonging to plain and 
undulating terrain. The positions at 10 points having distinct 
contrast are measured on three ortho images derived from 
different DEM resolution. Ortho image generated from 2.5 m 
DEM was taken as the reference and planimetric differences 
were computed at all the points. The results are tabulated in 
Table 3. 
Figure 4. DEM of Microwatershed for terrain Parameter 
retrieval 
The slope was calculated for each cell and was categorized into 
9 standard categories. Similarly the aspect was also calculated 
for each cell and categorized into 8 categories. The slope map 
and their categories are shown in figures 5a and 5b respectively. 
Similarly aspect map and their categories are shown in figures 
6a and 6b respectively. 
Difference in Location between Ortho images 
Generated (m) 
From 5m DEM & 
2.5m DEM 
From 10m DEM & 
2.5m DEM 
Longitude 
Latitude 
Longitude 
Latitude 
0.0 
0.1 
1.0 
-0.6 
0.0 
-0.1 
0.9 
-0.6 
0.0 
0.1 
1.0 
-0.5 
-0.1 
0.1 
1.0 
-0.5 
0.0 
0.0 
1.1 
-0.5 
0.1 
0.0 
1.1 
-0.5 
0.1 
0.0 
1.1 
-0.5 
0.1 
0.0 
1.1 
-0.5 
0.0 
-0.1 
1.0 
-0.6 
0.0 
0.0 
1.0 
-0.6 
Figure 5a. Slope map 
Table 3. Planimetric Difference in Ortho image generated using 
DEM at different locations 
Retrieval of Terrain Parameters 
DEM corresponding to a micro watershed and are shown in 
figure 4. Slope, aspect and drainage network has been extracted 
from DEM. Slope and aspect is an important parameter in the 
study and modeling of soil erosion, landslide, watershed 
management and hydrological applications. 
(40 - 75) 5% 
SLope (Pie Chart) 
r (75-90) 0% 
(0-1)1% 
r (1 - 3) 5% 
r (3-5)6% 
(25 - 40) 34% 
(5 - 10) 14% 
(10 -15) 12% 
0(0- 
1) 
■ a- 
3) 
□ (3- 
5) 
□ (5- 
10) 
■ (10 
-15) 
a (15 
-25) 
■ (25 
-40) 
0(40 
-75) 
■ (75-90) 
(15 - 25) 23% 
Figure 5b. Slope Categories 
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