IX-B4, 2012 
ing coordinates of 
V and orthoimage 
| was presented in 
oimage. Most of 
between roads or 
  
int 
hoimage and on 
in distance which 
were analyzed 
90% of the points 
naller than values 
vo) Checkpoints, 
zure 1. Altimetry 
> 32 Checkpoints 
lus the difference 
gain results were 
h limits for error 
ed in table 2. 
ood and they are 
n of equivalent 
llts are presented 
oints used in the 
observed (2.651 
iracy compatible 
1:10,000, whose 
ation limit is 5 
for 90% of the 
| 3 presents the 
till the limits 
cale. 
Percentage 
(%) 
  
   
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B4, 2012 
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia 
  
  
  
A 5,0 24 80.0 
B 8,0 28 93.3 
C 10,0 29 96.7 
  
  
  
  
  
  
Table 3: Classification of the results according to the PEC for 
the scale 1:10,000 
According to the offset values observed at checkpoints, we 
calculated the average and standard deviation obtaining 3.49 
meters and 2.65 meters, respectively, for the 30 checkpoints 
used in this evaluation. There appears to be no significant trends 
in the displacement, since the mean differences in x and y (E 
and N) are 0.11 m and 0.66 m respectively. These values are 
quite low when considering the pixel size (2.5 meters). 
Figure 3 shows the distribution of errors (displacement) at each 
checkpoint. It shows a distribution without major trends, 
although the largest displacement occurred at a point with high 
elevation. In the remainder of the area, including other points 
with higher elevations, results are homogeneous, indicating that 
the orthorectification was able to correct the relief effect. 
got 
Figure 3: Planimetric errors distribution 
3.2. Altimetric Evaluation 
Considering the tolerances established in the PEC, 94.12% of 
the checkpoints presented errors till the limit (5 m tolerance) for 
class A of the 1:25,000 scale. The standard deviation calculated 
is also under the limit (3.3 m) for class A of the same scale. 
LE90 (Linear Error for 90% of the points) was calculated, 
obtaining 3.75 meters. Table 6 below shows how the accuracy 
of the DEM altimetry can be classified according to the PEC, 
taking as reference the scale 1:25,000. 
  
  
  
  
  
Class Tolerance Checkpoint Percentage 
(meters) Number (%) 
A 5.0 32 94.1 
B 6.0 32 94.1 
€ 7.5 33 97.1 
  
  
  
  
  
Table 4: Classification of the results according to the PEC for 
the scale 1:25,000 
Just asin the planimetric evaluation, it was observed no 
significant trend in the altimetric errors, since the 
average was calculated in -0.427 meters. The highest 
error was 10.073 meters. 
Figure 4 shows the distribution of the checkpoints errors. In this 
figure its possible to observe that, despite the highest error is 
located in a high altitude area, errors are well distributed, in 
general. 
  
Figure 4: Spatial distribution of the altimetric errors of the 
CARTOSAT DEM 
Like any DEM generated by automatic correlation from 
stereoscopic pairs, there is failure in areas which the correlation 
is not good. In general these gaps occur in areas with clouds and 
their shadows, in places where there is a blockage in one (or 
both) of the scenes of the pair; in very homogeneous area. After 
verifying that these failure areas occurred where it was 
foreseeable, the DEM was generated again, using the option to 
fill the voids and filter results. Figure 5 shows the areas where 
faults were located in. Most of those failures occured in the 
southeastern part of the area, probably, because few GCPs were 
used there. 
  
Figure 5: Areas of failure (in yellow) on the CARTOSAT DEM 
4. CONCLUSIONS 
According to the results, CARTOSAT DEM presented 
planimetric accuracy compatible with the specified to the class 
B of the scale 1:10,000 and altimetric accuracy compatible with 
the specifications for class A of the scale 1:25,000. 
The results for the DEM CARTOSAT were according to what is 
expected for a sensor with its characteristics. Cartography 
Coordination of IBGE (Brazilian Institute for Geography and 
Statistics) presented the evaluation of a DEM generated from 
Triplet data of ALOS/PRISM, which has spatial resolution 
equal to the CARTOSAT (IBGE, 2009). Results were very 
similar. 
Although in the present work Orthoimage and DEM derived 
from Cartosat-1 data showed planimetric accuracy compatible 
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