I was interested in easily seeing the line sight horizon area form my home QTH without climbing on the roof of the house and having a look. From my attic skylight window I can see 5mile south to the Westbury White Horse and 20km North East to Kings Hill and in-between lays Olivers Fort above Devizes at 17km.
Using Memory-Map OS software I started drawing tracks radiating from my co-ordinates and then obtaining the elevation plot for each track. This gave good indication of where the horizon paths for each individual bearing but is difficult to visualise the combined results for a 360 deg blanket coverage.
www.ukrepeater.net have predicated coverage maps for each amateur radio repeater in the UK, it was something like that I was after. Bit of research turned up RADIO MOBILE...

Radio Mobile is a free and powerful tool for plotting RF patterns and predicting the performance of radio systems.

With the aid of the websites listed below I was able (after a bit of fumbling and re-reading) to install and set up Radio Mobile under WINE on a Ubuntu 11.04 Linux system and obtained pretty elevation data maps and RF coverage plots for my station.
I found not all the information found in the tutorials to be relevant and had some read more complicated than need be, but I managed to make progress and some sort of sense between them.

Running Radio Mobile on Linux with Wine: (Install hints)

The official download and installation instructions: (general install procedure to follow)

Using Radio Mobile for Windows: (clear and easy tutorial and most helpful in early stages after install especially good are the screen shots of settings - but only good so far for me as it's WIFI specific set up)

Radio mobile Quick Start : (I found this one hard on the eyes in its Web 1.0 style, confusing layout and made almost unusable by the horrendously slow loading of unoptimised screen grab images which is a shame as someone as put a lot of time into the information it contains. But should provide a comprehensive reference point after getting first plots from the other tutorials.)

My maps...
(place holder - to be added)

Reading slowed up with time taken up with other activities with the improved seasonal weather. Doesn't help getting stuck in a 1000 page Stephen King with no escape.

Oh... I haven't read a Stephen King novel since I was in my mid-teens and after being stuck Under the Dome I plan on reading the next one in about 20 years time... never had such claustrophobic read.

It more Nick Stone doing his do, I likes. Didn't like the price tag for the kindle download though.

Am stuck in another 1000 plus page novel randomly picked from my kindle library, hard going as mainly reading at night and fall asleep after only a few pages.