Contour and Copy Terrain Grid

Use this dialog to contour the terrain grid (create elevation curves, contours) or copy the terrain grid to a point cloud.

Where can I find the dialog?

Right-click in the vertical list field and select Contour/Copy Terrain Grid...

Selection Limitations

If a polygon is selected in advance, only contours and grid points within that polygon are included.

Example of boundary line

If no polygon is selected, the entire terrain model area is used.

Difference Layer

This option is used to create isolines for differences between two layers. An isoline on a map is a line drawn through points with the same value.

Example

If you want to find the line where two layers intersect:

• With only the selected layer and the difference layer set to 00: None, you get results corresponding to the selected layer.
• With the difference layer set to one of the other layers in the drawing, you get results corresponding to the difference between the selected layer and the difference layer.
• At the intersection of the selected layer and the difference layer, elevation 0 corresponds to the intersection between the two layers.

Result Options

There are two result options in this function:

1. Contours Generated from Terrain Grid

Generates elevation curves from the selected layer. The user sets settings for contour interval and property code.

Example of contours generated from terrain grid

2. Terrain Grid Copied to Point Cloud

Copies grid points to a point cloud object.

Example of terrain grid copied to point cloud

For this option, you can also check to ignore grid points in flat areas and extract coincident line segments from an application layer. The methods for this are described below.

Result Application Layer

You can choose which application layer the result will be placed on.

Tip

If you select blank for the result application layer, the data will be placed on the clipboard. You can then paste it into any application layer you want.

Method for Removing Points in Flat Areas

This option provides a grid that is better suited for triangulation, as redundant points are removed, resulting in a smaller triangle net.

Procedure

Illustration of method for removing grid points

For a grid point P:

1. Calculate elevations for P and all neighbors (9 cells)
2. Check that all 9 cells are within the boundary contour
3. Calculate the 3D plane equation using grid points P1, P2, P3
4. If all 9 points have a Z deviation from the calculated plane that is less than the minimum parameter, grid point P is removed

Info

The method ensures that grid points near sharp edges and boundary contours are retained.

Method for Extracting Line Segments

To achieve the best possible triangle model, you can supplement the point cloud with break lines.

Process for Extracting Line Segments

You must have an application layer with the break lines that helped define the intervention in the terrain grid, for example:

Original break lines that define the intervention in the terrain

You can then extract the line segments that still coincide with the sharp bends in the point cloud:

1. All lines are split into small line segments according to the grid size
2. Line pieces that coincide with sharp edges are then joined together
3. Redundant points are removed

Extracted line segments that coincide with sharp bends

These lines help preserve sharp bends in the subsequent triangulation:

Resulting triangulation with well-defined sharp bends