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2. Module for Orienting the photograms 
The points of the non-metric image are coincided and the result 
are co-ordinates of the support points from scanning. The 
scanning is visualised in polar projection by using either value I 
intensity or RGB. 
A table (x,y) or sheet (x,y,z) is created of the land, used to 
proceed with making the estimate of the DLT parameters. 
It is superfluous here to reiterate the specifications in 
distribution of the points for a sound estimate of DLT 
parameters. Please review the articles by the authors, given in 
the bibliography, for further information. 
It is important to remember that the sheer number of points in 
the clouds allows us to have a number of control points much 
higher than the number strictly necessary and with a spatial 
distribution that can be optimally defined by the operator. 
  
   
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Figure 8: Module for Orienting photograms. Collecting points 
  
  
Figure 9: Module for Orienting photograms: corrisponding point in oriented photo 
After orientation, it is possible to experimentally verify the 
accuracy of the estimate of the parameters by activating links 
and visualising the correspondence between the LASER 
window and the non-metric image. 
In fact, this involves application of the DLT equations that 
present the passage from land co-ordinates to image: 
XYZ —xy. 
For every point on the “LASER” representation, there is a 
corresponding trio of co-ordinates. 
3. Module DEM 
This enables DEM to be generated starting with the points 
cloud. It is possible to select points based on an interval of the y 
co-ordinate, or based on a distance from the X,Z plane of 
projection. 
This option reveals the purpose for which the software was 
originally written: the generation of orthophotos of 
architectonic brickwork that can be reasonably assimilated to 
portions of vertical plane. 
Generating DEM is done as follows: 
- definition of the dimensions of the pixel of the orthophoto 
(according to the scale of representation); 
- creation of an empty digital image as large as the final 
orthophoto; 
- assigning each pixel the y value (elevation) by means of 
interpolation based on the Nearest Neighbor method from 
the laser points. This gridding method assigns the value of 
the nearest point to each grid node. This method is useful 
when data are already evenly spaced, but need to be 
converted to a grid file. Alternatively, in cases where the 
data are nearly on a grid with only a few missing values, 
this method is effective for filling in the holes in the data. 
  
Figure 10: Module DEM 
Interpolation can also be read from a file generated by special 
gridding programmes in order to use different interpolation 
algorithms (eg. Inverse Distance to a Power, Kriging, Naturale 
Neighbor, Triangulation with Linear Interpolation). 
—305—