Simplify Geometry

With this command from the context menu, or as part of the import options or via the Modify Objects dialog, polygon objects can be simplified by deleting intermediate polygon points.

This saves memory space and increases calculation speed since calculation occurs for each segment delimited by two points. In particular with imported files, the geometry of terrain contours and traffic lines (roads, railways) are often with much detail. By applying the command Simplify Geometry, a considerable data reduction which does not impair the accuracy can be achieved.

In 2D, the method corresponds exactly to the Douglas-Peucker algorithm. When using the Vertical option, the approach does not exactly match the 3D version of Douglas-Peucker, as CadnaA checks horizontal and vertical distances separately.

Dialog options

• Horizontal: The entered condition is checked just for deviations in the xy plane and applied if necessary.
• Vertical: If this option is activated, a vertical deviation in the z direction can be specified. This condition is then additionally checked and applied if necessary. In this case both conditions - horizontal and vertical - must be met in order to trigger the stitch.

Example

The example makes use of a road having many polygon points.

Initial situation: road with many polygon points

On the dialog Simplify Geometry, 1 m is entered as a horizontal criterion. This causes the deletion of all points which meet the this criterion.

After closing the dialog with OK, the road section is straightened.

Final situation: remaining road with three polygon points

Just three polygon points remain, since all other points deviate to their respective neighboring points by less than 1 m.