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Basic Information

Name of Program



January 1999


April 2008


contour line
volume method

Short Description of Functionality

The program ZWISCHENPUNKTE generates topographical information by spline-interpolation. It can be used for a better interpretation of topographical data which is based on depth contours. Also its possible to generate depth information on a polygon to be used as a system boundary.


  1. input-file (filetype zwischenpunkte.dat)
  2. file with depth contours (filetype insel.dat)
  3. (optional) file with profiles (filetype digi.gkk)
  4. (optional) file with a talweg-polygon (filetype digi.gkk)
  5. (optional) file with a system boundary polygon without depth information (filetype digi.gkk)


  1. file with generated depth information (filetype geom.dat)
  2. (optional) file with points of intersection of depth contours and profiles (filetype geom.dat)
  3. (optional) file with depth points which define depth contours (filetype geom.dat)
  4. (optional) file with generated profiles (filetype digi.gkk)
  5. (optional) file with a system boundary polygon containing depth information (filetype insel.dat)


The points of intersection between depth contours and profiles are found out. On each profile the points of intersection are used as fixed points for a spline interpolation. Depth information is generated by evaluating the spline-functions between the depth contours. The evaluation is carried out at points which are located at constant distances on the profile and/or at a constant number of points which are centered equidistant between two depth contours. Profiles can be defined in an input file, or they will be generated by the program. The generation of profiles can be carried out either by generating profiles right-angled to a talweg-polygon (which is defined in an input file) or by generating profiles right-angled to the bank. The bank is defined as the contour line at MThw level (mean tidal high-water). Profiles which cross more than one channel are divided into new profiles (which don’t cross more than one channel). To avoid generation of not plausible depth data a smoothing routine is carried out after evaluating the spline-functions. The smoothing is carried out, if the depth value of a generated point is not within the depth intervall of the closest depth contours that surround the neighbouring depth contours to the point. The smoothing is carried out by replacing the spline-points by points of a second degree parable. The extrem value of the parable is defined by a smoothing parameter in the input-file. Also its possible to suppress output of spline-points which are out of a depth intervall surroundig the depth values of the neighbouring contour lines. Also its possible to suppress generation of spline-points at profiles where the distance between at least two contour lines is greater than an maximum distance. The maximum depth intervall and the maximum distance must be defined in the input file. An extra function allows to evaluate depth information on an polygon which defines the system boundary. The depth information is found out by evaluating the intersection points of the polygon and the contour lines. It is also possible to generate depth information between the intersection points as described above. It it also possible to generate depth information by linear interpolation of the depth information at the intersection points. The depth information at the angles of the polygon is calculated by the mean value of the neighbouring intersection points.

Program(s) to run before this Program


Program(s) to run after this Program


Additional Information



Additional software


Original Version

J. Fräßdorf


working group PRE


see also Erzeugen von synthetischen Tiefenpunkten aus Isoliniendaten, published in Supercomputing News No. 4/1998 (available in German only).

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