Create centroids from DTM triangles

This function allows you to create a string file which contains points at the centroids of the triangles in a DTM. The Z value of the points produced will depend upon the processing function specified. This gives you the ability to smooth a DTM to remove extremely high and low points from the data.

To run this function: Choose Surfaces > DTM file functions > Create centriods from DTM triangles, or...

In the Function Chooser, type DTM CENTROIDS, and press ENTER.

The output of this module can be used to create a DTM from which contours can be extracted. The module has the effect of increasing the density of the points in the model and provides the ability to smooth a surface because of this.

Extract centroid data from a DTM form

Define the DTM

The DTM to be processed must be defined by entering the Location, Object ID and Trisolation ID, of the DTM.

Use descriptions

You must specify if the point description for processing should be recalled.

Object ID

Select the object from the DTM to be processed.

Trisolation ID

Select the trisolation from the selected object for processing.

Field required

If you wish to use descriptions then you may enter Z or D1 or D2 etc. to define which field is to be used for the function specified. If you specified not to use descriptions then the only valid response is Z.

The values from the specified field are used to determine the value for the triangle centroid.

Calculation required

The DTM Centroid function required must be entered. There are three valid entries. The function name and result are shown below.

@MEAN	The selected triangle values are meaned to create the value for the triangle centroid. Z ₁=(Z₁+Z₂+Z₃)/3
@LOGMEAN	The selected triangle values are logmeaned to create the value for the triangle centroid. Z₁=10 ^{(LOG(Z1)+LOG(Z2)+LOG(Z3))/3}
@SLOPE	The value of the triangle gradient in the direction of the maximum gradient is used as the value for the triangle centroid.

Define file to create

The Location and ID number of the file which is to be created must be entered.

Result

A new string file is created with a point at the centroid of each triangle in the DTM.