primary 
Complete maps Lire mapped 
Revised 
| maps 
Upgraded 
— key-items 
Semantic Zt eributes 
Thematic 
  
OUTPUT 2 
I content —— :ey-items 
Metris ——lattributes 
Digital 
—— Presentation Graphic j specifications 
Textual 
: Semantic eps : 
otre ; specifications 
Metric 
Fig. 4: Description scheme for the output. 
The link between the description of input and output is established by 
the specifications for the process and intermediate product. 
5. AMP procedure 
A suitable way of modelling the process is by a matrix, representing the 
domains versus the process stages (figure 5). The operation begins in the 
preparation stage by verifying terrain relief. Then it sequences along 
the path through both domains, as indicated in figure 5 by arrows. The 
nucleus of  AMP represents the geometric transformations, especially the 
"image-to-DTM surface” transformation. On-line systems perform these 
transformations in real-time. 
In the following section, 
tranformtion. 
attention is focused on the image-to-model 
6. Image-to-model transformation 
To this end, any image with known geometry can be used, provided that the 
corresponding DTM data are available. Corrections for determistic errors 
can be included. 
The computation comprises two stages: 
— External orientation (or determining the rotation matrix), which re- 
stores the image rays in space; 
- Ray intersection with the DTM surface. 
The second stage is usually iterative, by applying a feedforeward (RADC) 
or a feedback (ITC) process. 
— The  "Photo-Carto Interface System" 
Development Center (RADC) begins the 
developed by the Rome Air 
process with a Z-plane, which is 
above the highest terrain point in the 
Then Z is incremented by dZ in the "top 
tersects the DTM surface. For each 
intersection point are caluclated. Then 
image (figure 6). 
down" sequence until the ray in- 
Zi-plane, the Xi, Yi of the 
the corresponding terrain height 
  
Hi is determined by interpolation from the DTM data. The sign of the dis- 
crepancy  /Zi-Zi-Hi indicates whether the point i on the ray is above or 
below the DTM surface. Thus, when 4Z; becomes negative, the iteration can 
be terminated. For computation of the adjacent points, the Z-level of the 
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