3.2 Depth contours 
The nature of data points in generation of deptn contours 
is often quite different from those in usual contouring. 
Measuring of the data points is not selective and some 
characteristic information may be lost. Still in many 
technical needs usual contouring methods can be used. If, 
however, depth contours are used for navigation purposes 
the generation of depth contours should be handled as a 
special application. Besides interpolation extrapolation 
of depth contours may be needed in order to reveal the 
critical shallow places (local valleys). In Finnmap Oy 
depth contours have been drawn in connection with mapping 
of a harbour area and building of underwater pipelines. 
The measurements are usually done in a profile form and 
the location of the data points is often not given in.x- 
and y-coordinates but rather in measures of direction and 
distance or cross section of two directions or angles from 
known points ashore. ESKO has also a geodetic routine for 
calculating of coordinates from these measurements. 
A function that has often been used in connection with 
depth contouring is editing of the triangle net. Triangles 
need to be deleted in order to leave e.g. platforms and 
islands outside the model area. 
4. STREET PLANNING 
For the time being we are working with one of the most 
interesting applications of ESKO. A consulting committee 
that acts as an intermediary in supplying computer prog- 
rams for the use of municipalities (KATKO) has ordered 
programs for municipal street planning from Finnmap Oy 
and two co-operating companies. An essential part of the 
system is a digital terrain model. However, some new and 
interesting demands have been made for the function and 
composition of the DIM 12/. 
The digital terrain model includes following data: 
- elevation data (DEM) 
- subsoil exploration points 
- storm water levels 
- loeation of the streets 
The data structure is shown in Figure 3. 
The soil type model is a result of information about the 
borring points, triangulation and manual interpretation 
of the soil type surfaces. 
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