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Mapping Radio Coverage, And Viewing It In Google Earth

JS writes, “I am doing a very small wireless operation in Catalonia, and it would be very interesting to have the coverage map of the antennas. Do you know any free (or cheap) tools to do that and place it on Google Earth?” I know of two free Windows tools useful in analyzing radio coverage. The first one is a general purpose terrain analysis program that will give “quick and dirty” plots of line-of-sight coverage and required antenna heights fairly easily. The second, more sophisticated program is specifically designed for determining broadcast coverage and signal strengths, but is also more difficult to use. Getting the data products into Google Earth can take some work, but can be done.

The first program is MicroDEM, the “Swiss army knife” of terrain tools. MicroDEM can easily produce line-of-sight plots from DEM data, showing where the antenna is visible from in a straight-line direction:



Where green marks visible areas from the starting point, while red marks areas blocked by terrain. You can also easily create a viewshed, showing the entire area that has line-of-sight visibility to the antenna:


Using the process described in this post, you can convert the viewshed into the standard shapefile format. Using free GIS software like MapWindow, you can plot the shapefile results over a topo map:

Line of sight viewshed for radio coverage

But you can also convert the shapefile into KML format for display in Google Earth:

Line of sight LOS viewshed displayed in Google Earth

Tip: Zoom into the area first before loading in the KML file; depending on its size, and the speed of your computer, having it loaded in and turned on can slow things down ….. a lot.

MicroDEM also has a couple of additional radio-related functions. If do a Line-Of-Sight profile, right-click on the graph, select LOS Parameters, and check the box marked “Fresnel Zones”, MicroDEM will draw the first Fresnel zone, and outline in maroon the inner 20% which shouldn’t be blocked by any obstacles:

Line of sight graph with Fresnel zones plotted

You can also create a map of required antenna heights from a DEM using MicroDEM. From the “Raster GIS” menu, choose “Required Antenna Height”, then double-click on the antenna site. Enter the height of the receiver antenna above the ground, the receiving range, and the minimum vertical standoff:

antenna height options

And get this map, with required antenna height in meters plotted in color:

Required antenna height plot as function of geographic position

You can get a similar map for the required height of a flying transmitter.

If you save this map as an image, you can load it into Google Earth as a simple graphic overlay, and move and stretch it into the correct position. But it’s also possible to save it as a georeferenced GeoTiff image, and then use a program like SuperOverlay to convert it to a tiled image that will automatically be placed in the right position in Google Earth (I’ll be covering tiling in greater detail sometime in the future).

For more sophisticated radio coverage analysis, there’s Radio Mobile (images taken from the Radio Mobile website):

Terrain effects on radio coverage intensity in Radio Mobile

Terrain effects on radio coverage intensity in Radio Mobile

I’m not even going to try to cover the capabilities of this program, since there are a lot of them, it’s not necessarily the easiest program to use, and I’m not an expert in radio engineering. I will refer you to several sites with additional useful info and resources on Radio Mobile:

– A PDF of a presentation on Radio Mobile

– A tutorial/walk-through

– A quick start / installation guide, with downloadable PDF files of the entire website: also has a link to a program installer file (the Radio Mobile site has a piece-by-piece installation process)

– An active Radio Mobile Yahoo discussion group

Getting Radio Mobile results into Google Earth is left as an exercise for the reader :).

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