Points above / below DTM file

You can use this function to select or tag the points of a string file that are above or below a DTM. The points outside the DTM boundary are never selected or tagged.

To run this function: Choose Surfaces > DTM file functions > Points above/below a surface, or...

In the Function Chooser, type POINTS ABOVE / BELOW DTM FILE, and press ENTER.

Fields on the Select/tag points above/below a surface form

Field	Description
The DTM file
File name	The name and location of the DTM file that you want to use to tag points in the string file as being above or below.
Object ID	The object number of the DTM.
Trisolation ID	The trisolation number of the DTM.
The string files to be processed
File name	The file name and location of the string file that contains the points you want to select or tag as above or below the DTM.
String range	The range of strings in the string file that contain the points that you want to select or tag as above or below the DTM. If you leave this field blank, all of the strings in the string file are processed.
Define the output file to be created
File name	The name for, and location in which to save, the string file that contains the selected or tagged points.
Select data	Above: The points that are above the DTM are selected or tagged. Below: The points that are below the DTM are selected or tagged. If the DTM was created on the XY plane, the points that are considered 'above' a surface are the points that are physically above the surface and the points that are considered 'below' a surface are the points that are physically below the surface. If the DTM was created on a non-horizontal plane, the points considered 'above' the surface are the points lying in the 'towards' direction of the plane (along the section's Z-axis towards your viewpoint). For example, if a surface was created using The current view plane and the active view plane was: a vertical plane resulting from VERTICAL SECTION LOOKING EAST, then the 'towards' direction is to the West. Points to the West of the surface are considered 'above' the DTM a vertical plane resulting from VERTICAL SECTION LOOKING WEST, then the 'towards' direction is to the East. Points to the East of the surface are considered 'above' the DTM a vertical plane resulting from VERTICAL SECTION LOOKING NORTH, then the 'towards' direction is to the South. Points to the South of the surface are considered 'above' the DTM a vertical plane resulting from VERTICAL SECTION LOOKING SOUTH, then the 'towards' direction is to the North. Points to the North of the surface are considered 'above' the DTM
Operation	Select: The result file contains only the points that are above or below the DTM. Tag: The result file contains all of the points in the original string file. The points above or below the DTM are tagged with the value entered in the Value to assign field.
Description field	The description field that the Value to assign field is assigned to. This option is available only if the Operation is set to Tag.
Value to assign	The value to assign to the selected Description field. This option is available only if the Operation is set to Tag.
Flush the D-field	Selected: The description field that the value is assigned to is cleared of all existing values before the points are tagged. Cleared: The description field is not cleared before the points are tagged. The description field value is overwritten for the points that are above or below the DTM. All other points keep the same value in the description field. This option is available only if the Operation is set to Tag.

Output

A string file that contains the tagged or selected points is created and saved.