Terrain Data

Terrain features have the dominant effect on most long distance radio signal propagation. It is therefore very useful to draw maps showing terrain elevations. In order to use this selection, you must first configure the path of the terrain database in Databases>Terrain (this is discussed in more detail in the Databases chapter). To extract and display terrain data within the defined study grid, select Map>Terrain data. This brings up the Terrain Data dialog box shown below in which you can choose to plot a terrain map, select the display type, i.e. shaded relief or user defined color gradient, etc., and set the colors and levels that represent the terrain elevation. This dialog box can also be accessed through Map>Setup Map Layers by highlighting the terrain layer on the map list and clicking the Style button, as well as through the Map Layers list in the Project Pane.

Show Terrain Data

This checkbox toggles the activity of the terrain data layer. Check the box to generate and show terrain data.

Type of Terrain Plot

The type of terrain plots that are available are:

Flat grid – elevations between two levels are all the same color; i.e. 60-70m are red, 70-80m are green, etc.
Contours – similar to elevation contours on a topographic map
3D – set your colors and level breakpoints, and extract and display the data in 3d (not recommended)
Color Gradient – similar to flat grid, but 60m is red, 70m is green; elevations between 60 and 70m will change color from red to green.
Shaded relief – a light source is applied to the terrain data showing the changes in elevation by the shadows cast (recommended method of display).

Terrain contour line

Only applies to the contour plot type. Sets the width of the contour line displayed on the map.

Set Color Levels

You can set the levels, colors, and symbols for your terrain map by clicking on the Set color levels button. For all plot types except Shaded Relief, the following Terrain Color Levels dialog box will appear.

Number of Levels

Set the number of levels to make up your plot. The maximum number of levels is 40

Max/Spacing/Min/Set levels

These parameters read the current terrain database and populate the minimum and maximum heights found, and display the Spacing for the data based on the number of levels selected. The units displayed are controlled through the Map Menu>Units dialog box. To the right of each parameter is a button. The non-grayed out buttons control the range at the moment. In the above dialog box, the Max and Min are active, and the Spacing is grayed out, meaning the Max and Min are controlling, and the Spacing is derived from the settings in the two active fields. If you wanted, you could click the button to the right of Max, deactivating it. Spacing then becomes active, so the levels will be controlled by the minimum values set and the spacing set. To set the elevation levels for each of the levels selected in Number of Levels box, click the Set Levels button

Color

If you’ve taken the time to set the levels, you will usually want to set the colors that represent the levels. This feature works with the color selected in the color column of the dialog box. If you don’t specify the color for each level specifically, you can use the color options to set a range of colors. Begin and End work with the Number of Levels field: changes in one are reflected in the other. The color selections on the left control how colors are chosen when you click the Generate button. Generate uses the color in the first (Begin) and last (End) color box to decide how to apply color.

The choices are:

HSL Interpolation – uses Hue, Saturation and Luminance to change colors
RGB Interpolation – uses Red, Green, Blue values to change colors
Hue Spread – uses random Hue color values to change colors
Alternate – creates a color blend
Random Color – picks a random color for each level
Reverse order – reverses the Hue direction from Level 1 (for HSL Interpolation only)

When you have all your terrain map settings the way you want them, select OK. If this is the first time you’re extracting and displaying terrain data, you’ll see a progress bar appear showing the extraction of the terrain data. Once this completes, the extracted data will show up in your study grid. Once displayed, further changes to the color or level settings are applied immediately on exit of the dialog box. The data does not need to be extracted again.

For the 3D plot type, once you’ve set you colors and levels, you’ll want to change the view elevation and azimuth to see the data from an angle other than straight down.

Show distinct grid lines

Returning to the Terrain Data dialog box, when displaying data within the study grid, the bins that make up the study grid are not outlined. This prevents the screen from becoming unreadable. When you extract and display data, sometimes it can be useful to see the edges of the bins. A good example is viewing terrain in 3D. When you show the terrain and change the viewing angle, the only sense of change comes for the change of color itself. But because terrain has more level changes than we can represent, seeing these changes in the display can be difficult. If we show the outlines of the study grid bin, we can see the changes in angle of each bin relative to the others, which can make it easier to see the changes in the data. To activate, just drag the Show distinct grid lines slider to the left. The farther you drag, the darker the lines. Start by dragging a quarter of the way to the left, and check the results on the screen, then adjust from there. Checking the Display with lighting effects radio button uses the lighting controls from the Current View Setup dialog box.