DTM Options

When the Options is selected a window in appears allowing the user browse to the DTM file and load it as shown in Figure 1. When a file has been selected, click the Load button to load the information.

Figure 1 File controls window.

Blanking Elevation Value
This option selects what value to fill in missing elevation data points. -999 is the standard input for missing values.

Display DTM Map
This option displays the data file in the workspace when checked.

Min and Max Valid Elevation
These two input boxes let the user adjust the range of elevation values allowed by DTM Tool. By default, this range is usually set to -1,000 m minimum and 10,000 m maximum. The user can use this range to isolate unwanted elevations or to encompass all the elevation points in a very wide range.

Load Options
This frame allows the user to attach data to the data already loaded by clicking the Append Data box. The user can also adjust the size of the data points in the workspace by changing the value in the Diameter of DTM Points input box.

DTM Utilities
This frame offers two options to the user. The Scale It button allows the user to input a conversion factor that will convert the units from meters to another unit such as feet. The input window is shown in Figure 2.

Figure 2 Unit conversion input window.

The second button in this frame is Sub Set. Selecting this button displays the window shown in Figure 3. The various options available here are described in detail below.

Figure 3 DTM clipping window.

Clipping Region
The user is able to enter Min and Max values for X and Y of two defined points for clipping rectangle. If the Set to Data button is selected, the fields for X/YMin and X/Y Max values will fill in automatically based on DTM data file loaded. If the Set to Current View button is selected, the clipping region will be generated base on the screen view set by the user.

The user can also define the clipping region by browsing to the desired file then loading. The region outside of the clipping line will be cropped. In case the Invert Selection check box is selected, the region outside of the clipping line will be retained.

The user can save the region after clipping by browsing to the desired directory and naming the output file. Then click the Apply Clipping button for the changes to take effect.
  Figure 5 and Figure 6 show visualizations of DTM data before and after clipping by a polyline.

Figure 5 DTM data with clipping line before clipping.

Figure 6 Retained region after clipping.