Drape string range over DTM

You can use this function to drape a range of strings over a DTM. This sets the elevation of each point of the strings to the elevation of the DTM, at the same X, Y coordinates. You can also create new points wherever a string intersects a triangle edge. This allows you to create a range of strings that follow the relief in the DTM.

To run this function: Choose Surfaces > Drape string range over DTM, or...

In the Function Chooser, type STRING RANGE OVER DTM, and press ENTER.

Fields on the Strings over DTM form

Field	Description
DTM layer name	The name of the DTM you want to drape the strings over. Note: To select a DTM, it must be open in Graphics.
Object ID	The object number of the DTM you want to drape the strings over.
Trisolation ID	The trisolation number of the DTM you want to drape the strings over.
String range	The range of strings to drape over the DTM. Note: The string file in the active layer is used.
Interpolate new points	Selected: New points are created, by linear interpolation, where the strings intersect the edge of a triangle. Cleared: No new points are created.

Output

The Z value of each point on the strings is modified so that it is equal to the Z value of the DTM at the same X,Y location. If you selected Interpolate new points, new points are created in the strings where the strings cross the edge of a triangle.

When draping strings over a DTM created on a non-horizontal plane, the process is:

The DTM and selected string are transformed so that the plane is horizontal.
The overlaying process proceeds as for a horizontal plane surface.
The results are back-transformed to sit on the original DTM location.

Troubleshooting

Message	Description
`There are no valid DTMs loaded in Graphics`	This function cannot be performed as there are no valid dtms that can be used to drape the string range over.