The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
DEMs of the Drum Mountains that were derived from 
Cartosat-1 data from two different acquisition dates were 
used in this study: October 24, 2005, and November 4, 2005. 
Figures 3 and 4 show examples of the image data acquired 
and the derived DEMs. The derived data, both DEM and 
orthoimages, were compared to a number of existing data 
sets to assess their vertical and horizontal accuracies. Those 
data sets include the following: 
• National Elevation Dataset (NED) 
• Shuttle Radar Topography Mission (SRTM) DEM 
• Advanced Spacebome Thermal Emission and 
Reflection Radiometer (ASTER) DEM 
• Digital Ortho Quarter Quads (DOQQ) 
The following table provides a description of the key 
attributes for the Cartosat-1 data and each of the above 
comparison data sets. 
Sensor/Source 
Satellite/Source 
Spatial 
Resolution 
Datum 
Cartosat-1 
ISRO Satellite 
2.5 meters 
WGS84 
NED 
Various USGS 
Map Sources 
10 meters 
NAD83 
SRTM 
NASA Shuttle 
Mission 
30 meters 
WGS84 
ASTER 
NASA Terra 
Satellite 
30 meters 
WGS84 
DOQQ 
Derived from 
aerial photos 
5 meters 
NAD83 
4. Methodology 
This study assesses the accuracy of DEMs derived from 
Cartosat-1 data with three different digital elevation data sets, 
each of which is derived from a different source. The 
National Elevation Dataset (NED) is a 10-m USGS DEM 
dataset derived from best available map data sources. 
ASTER DEMs are derived from visible-near infrared data 
collected by ASTER on board the NASA Terra satellite. 
SRTM DEMs are based on a fixed baseline radar 
interferometry-derived data, acquired by a NASA Shuttle 
mission. DOQQ data are enhanced computer-generated 
images of airborne mission-derived aerial photographs. 
DOQQ data are primarily used to assess the horizontal 
accuracy (x, y), while the other three are used to investigate 
vertical accuracy (z). 
Table 1: Key attributes of the Cartosat-1 and comparison 
data sets 
Figure 4: Cartosat-1 Digital elevation model - Drum Mts. site 
Figure 5: Assessment methodology 
Figure 5 describes the assessment methodology followed in 
this study. The 2.5-meter Cartosat-1 data were processed 
with 10 meters postings to create both DEMs and 
orthocorrected data using the ENVI* plug-in software. The 
ASTER scenes of the Drum Mountains were similarly 
processed at 30 meters using ENVI and Silcast software, 
while the NED and SRTM data were retained in their 
original 10- and 30- meters resolutions respectively. Silcast is 
a Japanese software package developed to create ASTER 
DEMs. Each of these elevation data sets was subset to a 
USGS NED Data ( 10 m) 
Cartosat-1 DEM Data (10 m) 
Figure 6: Drum Mountains: Subset area for difference images 
Any use of trade names in this publication is for descriptive 
purposes only and does not imply endorsement by the U.S. 
Government. 
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