The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
with the comparable SPOT HRS have been reached (Jacobsen 
2004). Of course with the different GSD and different height to 
base relation the absolute vertical accuracy based on SPOT 
HRS cannot be as good like for Cartosat-1. Unquote. 
Lehner et al 2008 report realizing a DSM with 10 m grid 
posting over Mausanne test site with results as follows: For the 
Jan stereo pair, the mean difference with ref. DEM: - 1.4 m; S.D. 
of height differences w.r.t. ref. DEM: 3.8 m as computed at 4.82 
million point locations. For the Feb. stereo pair, these mean and 
SD are respectively -1.1 m and 3.53 m as computed at 6.14 
million point locations. The reduction in number of points 
matched for the Jan stereo pair is possibly attributed to the large 
roll angle used in acquiring the same (-13.6 degrees) to achieve 
overlap between the two stereo pairs. These results are without 
any classification of landcover or terrain slope constraint. They 
also report of achieving a 3.2 m SD by considering both stereo 
pairs together in a combined multiple stereo processing mode. 
Baltsavias et al 2007 report achieving a mean difference of 
0.01 and 0.02 m respectively for the 10 m DSMs generated with 
Jan and Feb stereo pairs with S.D. values 2.73 and 2.94 m 
respectively after computing and reporting a 3-D bias values 
between the respective DSMs and the reference DEM, which 
are approximately 3 m, -2.5 m and 0.3 m in x, y and z directions 
for both cases. Titarov 2008 reports an RMS error of 7.2 m with 
a mean error of 0.8 m as computed at 6, 358, 422 points of the 
10 m DSM derived over Mausanne test site while comparing 
with the reference DEM. Gianinetto 2008 reports generating 
DSM using the commercial off-the-shelf software ENVI V4.3 
with different grid postings from 2.5 m to 90 m and concludes 
that the results are meeting the Reference-3 D specifications and 
better as compared to the DSM from SRTM source. 
For the Warsaw stereo pair, Zych et al 2006 report an RMS 
error of 1.26 m as measured at 25 GCP locations and evaluates 
the DSM accuracy by comparing the results along three linear 
profiles. They conclude that Cartosat-1 stereo data is good for 
automated DTM generation (15-20 m) at least in flat areas with 
vertical accuracy comparable, or even better than IKONOS. 
Dowman & Mitchalis 2006 report achieving an RMS error of 
6.65 m using 6 GCPs. Titarov 2007 & 2008 report achieving an 
RMS error of 2.3 m with a mean error of 1.0 m as measured at 1, 
985, 266 point locations of the 20 m grid DSM derived over 
Warsaw test site. 
Lehner et al 2008 report of realising a 5 m posting DSM over 
Catalonia test site with a mean difference of -1.0 m and a SD of 
3.05 m as measured at 7.08 million points while comparing with 
the reference DEM. See Figures 1 and 2. 
4.5 Orthoimage Quality: 
Kay & Zielinski 2007 report: quote: Our tests show that it was 
comparatively straightforward to produce reliable products, well 
inside the expected performance of a modem satellite 
instmment, from 2 to 3m RMSE1-D (i.e. in either Northing or 
Easting directions) mainly using RPC bias method in LPS with 
just 6 GCPs. Unquote. Lehner et al 2008 have generated 
orthoimages using both Fore and Aft images using the DSM 
generated and compared them to assess the residual sub-pixel 
shifts between them as a measure of the DSM usability to 
generate orthoimages. They conclude that CARTOSAT-1 stereo 
imagery is well suited for the derivation of DSM and 
orthoimages with about half pixel lateral and 1-2 pixel vertical 
accuracy (la) in terrain with good pattern matching 
characteristics and moderate slope angles using a few well- 
defined ground control points. Armenakis & Beaulieu 2008 
report achieving a planimetric accuracy of the Cartosat-1 
orthoimage of 2 m with about -1 m bias in both x and y 
directions. The road network DLG1985 was superimposed and 
demonstrated a good matching between the image road features 
and the vector road data. 
4.6 Scale for Topographic Mapping: 
J. Zych et al 2006 report that data from Cartosat-1 seems to be 
very good and it can be used for topographic maps updating in 
the scales 1: 10,000 (only on agricultural terrain) and 
1:25,000. According to them, the Warsaw scene snow coverage 
lowers its usefulness for acquiring information concerning land 
use and cover. Nevertheless, the results suggest that the 
Cartosat-1 satellite images may be useful for updating 
topographic map contents and as a layer in miscellaneous GIS 
systems because they provide high planimetric accuracy and 
slightly worse interpretation capabilities due to recording only 
in the visible range of the electromagnetic spectrum by means 
of panchromatic sensors. Accordingly, the Cartosat orthoimage 
might be used to updating 1:10,000 scale topographic maps. As 
per B. Sadasiva Rao et al 2006, the geometric accuracy and 
information potential of orthoimages and DEM provided by the 
Cartosat-1 mission can be exploited for (i) updating 1:25,000 
and 1:50,000 scale maps; (ii) making fresh topographic maps at 
1:25,000 scale; (iii) making thematic maps at 1:10,000 scale; 
and (iv) contouring at 10 m interval. Armenakis & Beaulieu 
2008 report that concerning the topographic data acquisition, it 
is expected that there would be no problems using Cartosat-1 
data for planimetric data acquisition. The dynamic range is good, 
making terrain features clearly visible and terrain morphologies 
differentiable. The spatial resolution, at 2.5 m, enables 
acquisition of planimetric data at CTI’s 1:50,000 scale within 
the technical specifications (minimal dimension, various 
features required, etc.). Titarov 2008 reports that the map 
accuracy requirements differ depending on the regional 
regulation, but in general the orthoimage accuracy achieved 
corresponds to 1: 10,000 map scale. Nevertheless one should 
keep in mind that it may be difficult to recognize on the images 
all the objects that must be shown on the 1: 10,000 map. 
5. COMPARISON WITH OTHER OPTICAL STEREO 
SENSORS 
Jacobsen, Crespi et al 2008 report: quote: In relation to other 
satellites, the matching with Cartosat-1 models is extremely 
successful. Unquote. Here for their conclusions they have used 
two more Cartosat-1 stereo pairs over and above those provided 
under C-SAP, viz. Warsaw and Mausanne. Also see Table-5 
above adopted from Jacobsen 2007 and the remarks following 
the same comparing with SPOT-HRS. A. Gruen 2008 concludes 
that regarding the image quality, Cartosat-1 is better than 
ALOS/PRISM but inferior to Spot-5 HRS or HRG. Their 
remark w.r.t. SPOT-5 comparison is based on identifying 
certain types of noise in the Rome data set after converting it 
from 10-bits to 8-bits due to a constraint in their software. Also 
to quote Jacobsen, Crespi et al 2008, from the very high 
resolution optical space sensors, apart from being expensive, 
only a limited number of stereo pairs, taken from the same orbit, 
are available. The automatic matching of images taken with 
significant time interval is very difficult and not leading to 
satisfying results. J. Zych et al 2006 also report of the DSM 
derived from Cartosat-1 being superior to those obtained from 
IKONOS.