Elevation Layer in HDMapper™
Q: How can I show elevation information in HDMapper?
A: With TAP6.0.2153 or later and a Maintenance Subscription date of February 28, 2007, or later, you can create a layer showing elevation values.
The elevation layer is created from an area elevation grid (.GRD) file created by HDMapper. This is the same elevation grid file format used by SoftWright’s 3DDisplay software.
For example, suppose you have a map of an area you are interested in:
On the toolbar above the map, click the Elevation Grid button:
You will be prompted for the shapefile to write and the Grid Step value to use:
The Grid Step value is the distance between points in the rectangular grid created by the program. The label near the top of the form shows the dimensions of the area in the East-West and in the North-South directions. The label in the center of the form shows the approximate number of grid points to be created. Naturally, a higher number of points will take longer to create. Fewer points will improve the time to create the shapefile, but reduce the detail.
The “Add layer to map” checkbox enables you to automatically add the layer to the current map when the layer has been created.
By default, the elevation shapefile for the area is written to the same folder where the map has been saved. The default name for the file is Area Elev.SHP. You can change the location and file name if desired.
(Note that if you have not saved the map, a warning message will be displayed:
When a map is created by opening shapefiles to add layers, the map information is saved in the MAPPING\MAP FILES folder under the folder where TAP is installed, with a file name of SWHDMAP1, SWHDMAP2, etc. Typically if you want to save the map information, you can create a new folder under the MAP FILES folder and save the file with a name that will be helpful to you in the future.
Adding an elevation shapefile layer to the temporary map is not recommended if you want to save the map later. This is because the elevation shapefile will be overwritten in temporary location the next time you create a map. This is not a problem if you recognized that you are working with a temporary map. The warning message is displayed as a reminder. If you want to keep the map for future use, it is strongly recommended that you first save the map to a new folder and name as described above before adding the elevation layer. (Maps created by other TAP functions, such as coverage maps, are automatically saved in their own folders, so this warning will not be displayed if you add an elevation layer to one of those maps.)
Select the values you want for the elevation layer and click the Continue button:
Grid files that exceed 100,000 points cause a warning to be displayed so you can confirm this is what you want to do. Click the OK button to accept the settings.
A progress form will be displayed while the topo data grid file is being created:
The a progress form will be displayed while the elevation shapefile is being created:
When the files have been created, you will be prompted with the opportunity to set the layer levels you want to use on the map:
When the layer is first added to the map, it is the “top” layer, and there are no “break points” to distinguish between different elevations, so the entire map is a single color:
Click Yes on the “Set Layer Levels?” form so you can set the layer colors:
The Layer form is displayed, with the “Area Elev” layer selected:
(This is the same form you use to set other layer information, such as field strength levels in a coverage study.)
The default database field in the shapefile is the “GRIDELEV_M”, or “grid elevation in meters” value. The elevation shapefiles created in HDMapper include the elevation in meters or in feet. You can select the units you want to use with the pull-down list:
As with other types of shapefiles you can use the Add button to add individual levels you want to display. However, TAP6.0.2153 and later includes a function to help set a number of levels at once. Click the Tools menu and select “Add Range Steps”
If the Add Range Steps menu is disabled, be sure you have selected the “Value Ranges” option in the upper left of the “Layer Theme Settings” section. The functions to “Add Range Steps” and “Set Range Colors” (discussed below) are only available for the Value Ranges setting and not for the “Single Symbol” setting.
The starting, stopping, and step values are displayed.
The initial values are the minimum and maximum from the selected database field for the layer, with a step, or increment, for a total of five break points:
You can change the settings as desired:
Click the Continue button to set the levels for the map legend.
If the settings result in more than ten levels, a warning is displayed:
Click OK to add the new levels:
The new levels are displayed on the Layer form:
(Note that the Add Range Levels function can be used with other shapefiles such as coverage studies to automatically assign a range of field strength levels to plot.)
The initial color settings are assigned with an algorithm to ensure unique colors for each level. For some uses, such as the elevations, it would be helpful to have a gradient of colors to show the gradual changes from layer to layer. TAP 6.0.2153 includes a function for this. In the Tools menu, click the Set Range Colors option:
The Range Colors form is displayed, showing the number of steps and the range of values, as well as the color gradient currently available.
You can change the end colors by clicking the Low or High label at each end of the gradient. For example, if you click the Low label, you can select a new color for that end of the gradient:
When you click the OK button to select the new color, the resulting gradient is displayed:
Click the Continue button to apply the color gradient to the Layer settings:
Click the Continue button to apply the settings to the map:
The legend entry containing the large number of elevation ranges can be hidden by right-clicking on the layer. A popup menu is displayed:
Click the Show Legend Details item to un-check it:
The Area Elevation layer is still displayed in the legend, but without all of the detail.
Since the “Area Elev” shapefile is the top layer, you can move it down (drag it with the mouse) to position it where you see the other layers you want:
You may find it helpful to set the fill property of some layers (such as county boundaries, etc.) to transparent in order to see through them. To change the settings for a layer, double-click the layer in the legend.
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Copyright 2007 by SoftWright LLC