Terrain Coverage Map

To view the coverage map, first download ucsc v1.0 Terrain Study (zip file). The zip contains the following files:

 

UCSC tile v1.0 (200f).kml

UCSC tile v1.png

coverage key ver1.0.jpg

 

The first two are needed for Google Earth. The third is a jpg image showing the color code used to map dBm on the coverage map.

 

Open Google Earth, then drag-and-drop the *.kml file directly onto it. After Google Earth automatically loads it (and the *.png file it depends on), you should be able to zoom, move about and control the opacity of the resulting terrain overlay file. We could have saved the whole thing as a single *.kmz file, but it would have lacked opacity control, and this feature is especially needed to draw any really useful conclusions from the study.

 

The UCSC study uses the Bullington propagation model rather than the more traditional and classic Longley-Rice model.  Bullington  assumes a smooth spherical earth without accounting for terrain factors, like vegetation, but is superior for accounting for shadow losses due to terrain obstructions - which is the chief form of propagation distortion we face here in the the Santa Cruz Mountains; Longley-rice does not account for these kinds of terrain anomalies but yields a more accurate estimation of distant field strengths due to ground and terrain features.  Hence, Bullington accurately models single and multiple knife-edge refractions.  The value of this model is primarily to see how fast signals comparatively drop off as they pass over topographic terrain obstructions. 

 

Terrain Analysis Program (TAP), a professional propagation prediction program owned by AC6P, was used to create this study.