TAP™ Area Elevation Grid
Q: How can I create a file of topographic elevation values in TAP6?
A: You can use the Topo Elevation Grid function in the TAP Map menu to create area elevation grid files.
With TAP6.0.2152 or later and a Maintenance Subscription date of February 28, 2007, or later, you can also create a shapefile of the elevation information for use in HDMapper™ and, if your TAP system includes the 3DDisplay™ module, you can create elevation file templates to view in 3DDisplay.
Open the Topo Elevation Grid function in the Map menu:
(The same function is also available in the 3DDisplay menu.)
The HDAreaGrid form is displayed:
Click the New button to create a new Task for creating Topo Area Grid files:
A new Task ID is assigned. Enter a description that will help you identify the Task later:
Enter the coordinates of the area boundary you want. You can also use the Template button to open the Area Templates database. The Area Templates database enables you to create and save the boundaries of areas you may want to use again in the future. You can also set the “step” value, the distance between points in the grid to create. The resulting estimate of the number of grid points is displayed in the Area section of the form:
You can adjust the coordinates and the step values to increase or decrease the number of points in the grid.
Select the topo data interpolation method to use and the types of topographic data to use for the elevation grid file:
Select the elevation units to use and the output format you want:
The SURFER™ grid file (.GRD) format is used by the Golden Software SURFER program as well as by the TAP 3DDisplay module. The other option (ASCII X-Y-Z) creates a comma-delimited file with one line of longitude, latitude, and elevation for each point. The ASCII format may be useful if you need the elevation data for use with other software.
Enter the name for the output file you want to create.
If you double-click the “Output File” section header on the form, and the Task Description has been entered, file names will be automatically generated using that description:
If your TAP license includes a Maintenance Subscription date of February 28, 2007, or later, you can also create a shapefile of the elevation information for use in HDMapper™ and, if your TAP system includes the 3DDisplay™ module, you can create elevation file templates to view in 3DDisplay. Use the “Write 3DDisplay Template” and the “Write Shapefile” check-boxes to enable those options.
Note with TAP 6.0.2173 or later, and a Maintenance Subscription date of May 31, 2007, or later, you also have the option to automatically launch the 3DDisplay program to display the 3D view, and HDMapper to display the shapefile. Using the HDMapper option to display the shapefile also will give you the opportunity to use the Google Earth function in HDMapper to display the information.
Checking those boxes will cause the program to launch the display program automatically with the created grid file elevation information.
Click the Save button to save the Task settings:
Click the Run button to execute the Task and create the grid file:
The Task(s) to Run form is displayed. The form enables you to select several Tasks to run in a “batch” mode. Any Tasks you have edited and saved during the current session are marked by default. Click the Continue button to start the Task execution.
A progress form will be displayed during the topo elevation retrieval:
If you selected the option to write the elevations to a shapefile, that progress is also displayed.
Using the Area Grid File with 3DDisplay
If you selected the option to create the 3DDisplay template file, you can use that file as any other grid file in 3DDisplay. Open the 3DDisplay function:
When the 3DDisplay form is loaded, use the Load Template button in the File section to load the template:
Select the template you want to use:
If you are prompted to clear previous settings, click Yes:
Click the yellow ReDraw tab to refresh the display:
The surface representing the grid file is displayed:
You can use the 3DDisplay functions to change the coloring, lighting, scaling, etc. of the surface drawing. You can also use HDMapper to export topographic and coverage study maps to 3DDisplay templates.
Using the Area Grid File with HDMapper
If you selected the option to create the shapefile, you can use that file as any other shapefile in HDMapper. Open the HDMapper program:
Click the Add Layer button:
Select the layer you created:
The default location for the files is in the SHAPEFILES\AREA ELEV folder under the folder where TAP is installed.
The shapefile is displayed as a single-color layer:
To set the elevation levels you want to see, double-click the Legend entry for the layer:
The Layer form will be opened:
Since we want to show different ranges of values with different colors (rather than the shapefile default of a single color), click the Value Ranges option:
Select the database “field” or data value you want to use. The program uses this data column in the shapefile database to determine the color to draw the point based on your settings. The Area Elevation Grid shapefiles created by TAP include the elevation in meters or in feet. Select the units you prefer:
When you select a data field, the label to the right shows the number of data points and the range of values for that field in the file.
Now you can use the Add button to add individual elevation values as “breakpoints” just as you can with other shapefiles color settings. However, with a Maintenance Subscription date of February 28, 2007, or later, you can add a sequence of breakpoints at once. In the Tools menu of the Layer form, click the Add Range Steps item:
You will be prompted for the values to add:
The default settings are the minimum and maximum values in the file, with a step computed to create five ranges.
You can change the values to your preferences:
When you click the Continue button, a warning is displayed if the values result in more than ten legend steps. You can have more steps, but the warning is to alert you in case the result is more legend information than you want.
The new settings are added to the Layer form:
You can change the automatically assigned color settings if you double-click on the color block to the left of an entry.
Click the Continue button to see the settings applied to the shapefile on the map,
You can add other layers to the map and adjust the layer order as desired:
You can select the Area Grid layer for the MouseTips function to view the elevation at the mouse location as you move around the map:
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Copyright 2007 by SoftWright LLC