June 2011 | Q & A

Visualizing terrain with the slope map tool

SOCET GXP v3.2 offers multiple ways to visualize terrain data

What is the slope map tool used for in SOCET GXP?

SOCET GXP contains terrain analysis tools for in-depth geospatial awareness and analysis, such as Terrain Shaded Relief (TSR) displays. Now capabilities have been expanded to include more complex functionality for elevation slope and aspect analysis, terrain comparison, volume calculations, line of sight and registration. A slope map is a graphical depiction of the steepness of terrain or elevation data and is defined as an angle of rise over horizontal run. The slope can be calculated using many different algorithms, but SOCET GXP uses either average slope or steepest slope algorithms to determine the slope value for each terrain post. This is performed by imagining a center post with eight surrounding cells. The slope is calculated at each point in a grid by comparing the point’s elevation to that of its neighbors.

SOCET GXP v3.2 offers multiple ways to visualize terrain data

Figure 1. SOCET GXP v3.2 offers multiple ways to visualize terrain data using the Analyze group and Surface tab. In this example, LIDAR terrain data is being displayed as (clockwise from top left) continuous contours, TSR map, slope map and aspect map.

SOCET GXP v3.2 terrain shaded relief, or TSR map of LIDAR terrain data

Figure 2. A terrain shaded relief, or TSR map of LIDAR terrain data, is one option for visualizing terrain in SOCET GXP using the Analyze group and Surface tab.

To display a slope map:

  1. Import terrain data into the Workspace Manager and open it into a Multiport.
  2. From the Surface tab, in the Analyze group, click the Slope Map button.
  3. From the Display Properties window, select the Slope Map tab.
    • To display color range as a % grade, select the Display Ranges as % Grade checkbox.
    • Select the Average Slope or the Steepest Slope algorithm.
    • Click Apply to view changes.
slope map generated using the Average Slope algorithm from the LIDAR data

Figure 3. A slope map generated using the Average Slope algorithm from the LIDAR data with default color ramp displayed.

To change the slope color range:

  1. From the Display Properties window, select the Slope Map tab.
  2. Click the Slope Color Range… button.
  3. To change the color of a range, click the color block and a standard color selection palette displays.
The Color Range Selector post configuration

Figure 4b. The Color Range Selector post configuration.

Default Color Range Selector configuration

Figure 4a. The default Color Range Selector.


To control how the range is distributed over the number of ranges, follow these steps:

  1. With the Color Range Selector window open, place your cursor in the < Max column of the last (bottom) row, and enter 3 (or the lowest elevation you want for your terrain). When you click out of the cell, notice that the Min>= column updates automatically in the next row up (the number updates to 3).
  2. Edit the < Max cell, of the row associated with the automatically updated Min>= number. Enter 7. When you click out of the cell, notice that the Min>= column updates automatically in the next row up (the number updates to 7).
  3. When you are finished editing, click OK and the terrain color range will take effect, or click Cancel to exit the window and no changes occur.
slope map

Figure 5: Slope map. Green represents slope degree from 0 – 3%, yellow represents 3 – 7% and red represents 7% or greater.

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