Table 1 
Spatial 
Resolu 
tion (m) 
Swath 
(km) 
Spectral 
Bands 1.55-1.70 
(micron) 
No. of 
gray 
levels 
  
The following Data Products planned for IRS-1C 
mission can be used for Cartographic applications: 
1. Radiometrically corrected raw geometry 
Basic stereo Pair of PAN data. This product is 
useful for stereoscopic viewing and terrain elevation 
determination. 
2. Geocoded Data Products. These products 
are produced by mosaicing a number of data sets, if 
necessary, to give a toposheet compatible product 
in terms of format, resolution and layout. For IRS- 
1C these products are provided in 1:250,000 and 
1:50,000 scales for LISS-3 and additionally 
1:25,000 scale for PAN. 
3. Merged Products prepared by artificially 
merging the contents of registered high resolution 
PAN and low resolution multispectral LISS-3 data to 
produce high resolution multispectral data. These 
products are expected to allow better visual 
interpretation capability for linear features of interest 
in Cartographic applications. 
3.0 Issues in Terrain Mapping using Spaceborne 
Stereo Imagery 
The information content of a topographical map 
compiled by photogrammetric methods is provided 
by the ground resolution of the images expressed 
in m/line pair for camera systems and m/pixel for 
electro optical systems. The average resolution of 
an aerial photographic imaging system which is a 
combined influence of lens, film and the forword 
motion can be taken as ranging from 40 Ip/mm for 
systems not using forward motion compensation 
to 140 Ip /mm for modern system using forward 
motion compensation (FMC). The resolution in m/Ip 
is given by : 
Photo scale/1000 
Rp me 
R Ip/mm 
The values of Rm/ip for aerial photographs at 
1:50,000 scale photography is 1.25 and 0.357 for 
systems without FMC and with FMC respectively. 
Taking 1.25m/p as the resolution of aerial 
photograph and if the content of the image are to be 
as much as that of a 1:50,000 aerial photograph 
then the pixel size of the satellite image should be 
0.5m as given by the Kell's factor of 2 3/2 as pixel 
given by : 
Rm/ip= 2 32*R mypixel 
Even though the information content or 
features that can be extracted from any given 
imagery is determined by photographic resolution 
and scale or more directly by the resolved 
distance on the ground it is difficult to establish a 
linear relationship between map scale and 
resolution required as some features like roads , 
rail, canals etc. have to be depicted on a map 
irrespective of the scale. The smallest feature 
that can be depicted on a map is assumed to have 
a least dimension of 0.25 mm. In order that an 
object be identifiable on the imagery in medium 
contrast conditions, it must be imaged by at least 
5 resolution elements. It follows then that 
resolution required for imagery can be estimated 
as :- 
Ground resolution = 0.2 X 0.25 mm X map scale 
number 
=5X 10-5 X map scale 
number 
For 1:50,000 scale map product the required ground 
resolution = 2.5 m. 
824 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996