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and: 
- X, Yo and Z, are image center coordinates 
- c is camera constant (mm) 
- X, Y, Z are known coordinates for a number of 
objects well distributed in the image. 
- X, Y' are measured image coordinates for the 
same ground control points. 
which gives: D X' 7 -c(X-XoY(Z-Z4) (1) 
D Y' 7 -c(Y-YoY(Z-Z4) e 
D-c7-c 
The rotation matrix D is then solved from (1) and (2) by use 
of a number of ground control points (GCP's as X, Y and Z) 
measured in TOPIODK and in the image at their image- 
location (X', Y"), and the previous solved IO. When the 
rotation matrix for the image is determined, any map vector 
point (objects) with. known X, Y, and Z, can then be 
transformed backwards through (1) and (2) to their position 
in the raw image. 
3.3 VT, rectification workflow. 
The VT technique implementation in Mapcheck is presented 
as part of the production/control workflow for updating 
TOPIODK. 
3.3.1 First step - measuring ground control points — to 
determine rotation matrix by 1) and 2). KMS receives 
update-data from contractors in blocks each covering a 
photogrammetric model. A update-data model must be 
controlled geometrically with images rectified by already 
verified TOP10DK data - any of the two model-photos can be 
used. TOPIODK data from the database arc therefore used for 
the GCP measurements (automatically extracted according to 
the chosen photo's GPS photo-center). 
This is shown in fig. 1. There is no exact fit between the 
already verified vector data and the new images, though it is 
possible to recognize corresponding objects. Enough well 
distributed ground control points (GCP's) must be measured 
(selected with point snap) as TOPIODK database data (fig.1, 
Yellow crosses) and then connected to its corresponding 
pixel in the image (fig.1, Yellow vectors). 
To support the operator in this GCP-process, the vector data 
are shifted and turned immediately, when the user generates 
the first and the second ground control points, this makes it a 
lot easier to locate the following points. Qualified 
suggestions for ground control points, can be demanded to be 
automatically presented to the operator, in a reasonable 
zoom, for manual connection to its corresponding pixel. 
To evaluate coherence and accuracy of the measured points, 
the root mean square is calculated and reported to allow the 
user to accept the calculation errors and the final point 
distribution by visual judgment, or to measure more points. 
  
Figure 1. [nitial rectification measurement for Vector Transformation. Red crosses are measured fiducials. Yellow crosses are the ground- 
control-points as vector-object and the yellow connection vectors are pointed to corresponding G.C.P. image pixel. Height differences (Z) 
between GCP's are about 100 meters 
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