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4.2 PROCESSING OF ANTARCTIC IMAGES BY THE OrthoMAX SOFTWARE 
OrthoMAX is a high performance commercial software module which provides the following capabilities: 
• Triangulation (registration of the imagery to ground control) or Block Tool, 
• Stereoscopic viewing and mensuration (precise measurement of the geographic coordinates (X, Y, Z) from 
stereo digital images) or Stereo Tool, 
• DEM extraction and mensuration (production of a DEM in an exact ground space grid) or DEM Tool, 
• Ortho-rectification and mensuration (generation of ortho-images) or Ortho Tool, 
• Monoscopic mensuration (precise measurement of “blocked” and ortho-images) or Mensuration Tool. 
Ortho-images are produced according to the flow diagram in Fig. 7. The Block Tool permits to triangulate an 
imagery block (imagery and data associated with a single triangulation solution). Before triangulation (inside the 
Block Tool) some processing need to be done: 
1. entry and edit of GCP’s and tp’s with conversion of coordinates and evaluation of “sigmas” (standard 
deviations of pixel measurements along the three axes), 
2. measurement of tp’s or GCP’s on the images simultaneously. 
Figure 7. OrthoMAX Flow Diagram 
Table 7 is a subset of the coordinates of GCP’s in terms of their map projection and image sigmas; the Z 
coordinate is adjusted with an offset of +65m to take into account the difference from the ellipsoid. Here, as in the 
preceding case, the Lamberts Conformal Conic projection has been used. In OrthoMAX. the triangulation 
algorithm is based on an iterative (1 to 10) least square bundle adjustment of the data. A convergence value is set 
and used to determine when the iterations will stop. If the results are considered not very good the procedure of the 
Block Tool can be re-invoked and GCP’s and tp's (here indicated also with pass points) can be added or deleted if 
their residuals are very high. At the end of the triangulation process a full error report is produced for each 
iteration. Residuals for each GCP can be inspected; included in the report is also the standard deviation of unit 
weight, a measure of the conformance of the adjustment to its estimated parameters and parameter precision (value 
between 0.5 and 2; optimum 1). In our case, with a convergence value of 0.1 m, six iterations were required. 
Table 7. GCP’s Coordinates and Sigmas 
Point 
X-map (m) 
Y-map (m) 
Z (MHWM) 
X-sigma (m) 
Y-sigma (m) 
Z-sigma (m) 
Del5 
1000801.240 
2034206.970 
17 
20 
20 
10 
St 14 
1002745.660 
2033897.360 
83.01 
20 
20 
5 
Stl6 
1000713.310 
2032448.560 
253.95 
30 
30 
20