based on subtracting heights of the same point measured 
on the various models with the use of stereoplotter. 
Point identification is done through placingmeasuring 
mark on the model with the use of coordinate table, which 
is equipped with the plate, comprising points marked 
during first object measurement. Above mentioned methods 
are labour- and time-consuming. 
In described below method height deformations are obtai- 
ned subtracting heights of corresponding points, belong- 
ing to digital models from different dates. Digital 
model is acquired through readout of any point coordina- 
teg on the stereoplotter and through interpolation of 
heights of corners for uniform square grid. This allows 
to introduce automation of measurement and computation 
processes. Digital model was also used for volume deter- 
mination and for preparation of slope map. 
The system of programs Was elaborated for ODRA 1204 
and ODRA 1305 computers and implemented in some surveying 
enterprises in Poland. 
2. DIGITAL MODEL ACQUISITION 
2.1. Measurement of model coordinates 
Coordinates measured on relatively and absolutely 
oriented models are raw data for forming uniform digital 
terrain model /DTM/. At least 4 points with known terrain 
coordinates must be within each stereogram. These coor- 
dinates c8n be determined using one of aerotriangulation 
methods or can be measured directly on the ground. 
x,y,2 model coordinates are measured in locel coordi- 
nate system, its axes are parallel to stereoplotter axes. 
For each stereogram the system is oriented differently 
in relation to terrain coordinate system. Therefore 
for each stereogram adjustment points are measured. 
DTM points are the network of scattered points charac- 
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