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Find intersections of contour lines

Overview

This document explains the function of the Lua preset "Find errors in DTM". If problems occur when opening the 3D view or performing a calculation, the DTM is often the source of error. These problems can result in long times for initialization or the abortion of the calculation. When executing this Lua script, possible errors in the DTM are marked and can then be modified by the user.

Note

This Lua preset supports the user to find possible errors in the digital terrain model. No changes are made to contour lines / points or other objects in the calculation model. Error locations (e.g. an intersection of two contour lines) are marked with an auxiliary polygon.

Possible error types

Following error types are marked in the CadnaA model with a red auxiliary polygon:

  1. Contour lines with length < 0.1 m
  2. Two neighbouring polygon points of a contour line with the same x/y coordinate
  3. Two contour lines with same x/y coordinates of all polygon points, i.e. the same polygon in x/y‐plane
  4. Self‐intersection of a contour line
  5. Intersection of two contour lines
  6. Two contour lines with start or end point at the same x/y position (joint) but unequal height (z‐coordinate)

Notes:

‐ The error type is stored in the memo field of each marker (auxiliary polygon). ‐ Error type 4 is only calculated for contour lines with less than 2000 polygon points. ‐ Error types 5 and 6 are only calculated for contour lines with (NumberOfPolygonPoints1 * NumberOfPolygonPoints2) < 5 million.

Option „Round polygon points to 0.01 m“

If this option is activated, the polygon points of all objects of type “contour line” and “line of fault” as well as the coordinates of all elevation points are rounded to 0.01 m first. Afterwards the check for possible errors in the DTM is executed. Many of the errors that occur during initialization can be avoided in this way.

Attention: This modification of the DTM cannot be undone!