TAP™ File Types
Q: What are types of files TAP uses? If I have shapefiles do I need “Land Use” or “Topo” or "Surface Feature" files?
A: TAP uses a number of file types for the various functions, as described below. For information on specific files of each type in your geographical area, contact SoftWright sales:
Note that all values in this example are for demonstration purposes only. You should determine appropriate settings for your application.
Topographic Elevation data (sometimes mentioned in some of our FAQs as "topo data") provides the terrain elevation information, such as the data in the National Elevation Dataset (NED). These data files (from SoftWright or other sources, in one of our supported formats) are essential to use TAP to draw profiles or compute area coverage studies. The elevations of the ground between the transmitter site and the receiver location (fixed or mobile) obviously play a big part in the calculations. The common data formats we support include .BIL and DTED formats, sometimes available from other government agencies.
Mapping data (roads, rivers, county boundaries, etc.) information is used by TAP in the ESRI "Shapefile" format for drawing maps. We provide some basic features in shapefiles (usually separated into separate files for the types of features - roads in one file, rivers in another, interstate highways, etc.) and each shapefile can be used as a separate layer on a map. The widespread use of the shapefile format means you can use a lot of other files with TAP. You may have access in a large company or government agency to more customized and detailed shapefiles, such as boundaries for police precincts, etc. (The shapefiles must use latitude-longitude for the coordinate system. If your organization uses shapefiles in some other map projection, they will need to be converted to the WGS-84 coordinates in order to use them in TAP.) Plus, if you or someone in your organization uses other mapping software that can read the shapefile format, you can bring the TAP coverage results into that other mapping software, since our output is also written in the shapefile format.
Land Use data files provide information about what kind of development is found at each location. For example, using only the topographic elevation data you can compute the field strength at a particular location. But the success of using, say, a handheld mobile unit at the location might be different if the location is in the middle of an open field in the country, versus in the middle of a heavy industrial area with lots of electrical noise and other sources of interference. Using the Land Use data (or Global Land Cover data outside the US) enables you to model the differences in locations within your target coverage area. The FAQs describe how Land Use Loss Templates can be used to associate a particular land use classification at your operating frequency with a loss value to be added at each location. So, in the hypothetical example above, the field strength in the open field might be unaffected, but a value computed in an industrial area might be reduced another 8dB to account for the increased noise at that location.
Surface Feature files provide height information for obstructions on the surface of the terrain. Since the topographic elevation data values just provide the elevation of the surface of the ground, Surface Feature files provide additional height to represent buildings, vegetation, etc. The Surface Feature files are created by the TAP user based on knowledge of the area, or by importing from other databases.
To summarize,
(1) You must have Topo Elevation data in order to draw path profiles or compute area coverage studies. You can obtain the data files from SoftWright or you can use compatible format files from other sources.
(2) You can draw a coverage map using only the shapefiles provided with TAP (actually, you could draw a coverage map without any other shapefiles, as users have done in some countries before we had the shapefiles for those countries). You can also purchase additional shapefiles from SoftWright, such as detailed streets or population information for the US on a state-by-state basis. Or you can obtain shapefiles from other sources to use with TAP.
(3) You can use TAP without any Land Use data, but if you have the data and the Land Use module you can add the effects of different local environments as a part of the rf modeling for your coverage.
(4) You can create Surface Feature files to include the effects of manmade clutter or obstructions, or vegetation in the signal strength calculations. You can create Surface Feature files manually in TAP or import other databases. (One TAP user obtained a database of buildings from a city government and imported over 300,000 objects into Surface Feature files to use with the software.)
For information on any of these files for your geographical area, contact SoftWright sales.
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