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reo View 
  
The former plays the role of internal orientation computation of 
the aerial photos, creating an accessory file containing its 
internal orientation parameters. 
The latter provides the external orientation of photogrammetric 
block by using bundle block adjustment. 
No satisfactory results have been obtained by using this method: 
the principal reasons for which may be: 
» the use of paper copy of aerial photos, with the 
consequent high value distortion; 
the lack of calibration certificates for the aerial photo 
cameras which were used to take the photos, partly 
due to the fact that they were purchased back in the 
1970s and in part because of the specificity of original 
photogrammetric material. 
» the problems arising during the collimation of the 
control points, of which the coordinates acquired with 
GPS techniques in the field period were available. 
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Figure 2 — Example of dialogue windows of Stereo View 
software, modules Image Builder 
  
  
Figure 3 — Example of dialogue windows of Stereo View 
software, modules Triangulation 
  
53 
2.1 Acquisition of GCPs with GPS receiver 
The Ground Control Points used in the phase previously 
described, and in the next, were chosen principally due to the 
availability of points acquired in the field with a GPS receiver , 
trying to guarantee a consistent accuracy, by the error theory, 
bearing in mind the low number of points to locate. The GPS 
receiver used was the e-map model, produced by Garmin, hand 
type, low weight and of a suitable size to be transported on long 
journeys, and finally, relatively inexpensive. The accuracy of 
this kind of acquisition is of the same order of accuracy as this 
cartographic scale. This, principally, because of the proximity to 
the Equator, and so the wider GPS satellite cover. 
  
Figure 4. Acquisition session with GPS receiver 
3. REMOTE SENSING TECHNIQUES FOR METRIC 
SUPPORT PRODUCTION. 
Regarding the use of remote sensing techniques, we considered 
the kind of data elaboration that allows use as metric support 
complemented by that obtained with photogrammetric 
techniques. 
The image chosen was a Landsat 7 platform image, having 15 
meters panchromatic resolution, and 30 meters in visible range 
resolution. This image was chosen for a number of reasons: first 
because it satisfies the resolution characteristics for this medium 
scale support, and secondly for the high availability of archive 
images, in a zone where satellite cover is not so high. And 
lastly, for the lower price, compared to on-demand images. 
An orthorectification operation was applied on the image, using 
ground control points acquired with GPS techniques as 
described, during the field period, considering the altitude 
constant. This approximation was necessary because of the lack 
of a digital terrain model of the area involved, but is justified by 
the nearly absolute altimetric homogeneity of the area.