First, I don't know of any papers or open source for you.

An approach I took (using geological survey data, USA, lat/long/altitude), was to create an array[rows][cols] of height vs. XZ position. I chose a "corner" lat/long for the "lower right-hand corner," array[0][0]. Pick a delta-longitude and delta-latitude (I used something like 2 arc-seconds, I think, about 200 feet/~51 meters). Normalize your gps positions (assuming you can derive lat/long/altitude) to that "corner" lat/long, and divide by the delta-lat and delta-long to get indices into the array. Set the altitude.

Work your way left and up in the array, setting altitudes, for as many rows and columns as might be appropriate for limited memory.

Is that the sort of info you're seeking?

Also, you don't have to worry about curvature for a limited field-of-view ( a couple of kilometers to the horizon ).

EDIT: You may have to pay close attention to longitudes along the prime meridian (since that's in the territory) as you'll either switch from east-to-west or 360-to-0 on that line.

Because it was the precision of the survey data, I used 1800 elev points per degree. Of course, a degree of longitude changes length from north to south, but, if you don't need to be too rigorous, draw a box around Britain and use the size of a degree at the center.

From my helicopter app (I think NED is our National Elevation Database):

// refining the display of NED data// for compatibility with the NED database, use cells 71 quads on a side, a quad being ~202 feet or 1/30th of a nautical mile, or// 1/30th of an arc-minute or 1/1800 of a degree. Each database record (1 degree on a side) has 1800x1800 data points.

(We Yanks still use the British foot)

EDIT: a "quad" was what I used to draw 2 triangles for the terrain. It's a little "blocky," with changes of elevation only every 200 feet (~62m).

That's about 1.3Mb (using (4 byte) floats) per 1-degree-square-array, maybe too big for iPhone. Either use smaller arrays, or larger deltas.

If you want to muck about with conversions, store the altitude in 2 bytes (0-65535) and cut the array size in quarter. The UK doesn't have a lot of high altitudes (Scotland, maybe) so that precision may suffice.

This calculator can help you decide.

EDIT: By the way, the bookkeeping for which rectangle(s) need to be displayed when you're near an array boundary will drive you nuts. But you asked.

EDIT2: FYI, using 1-degree records, my database for about 1/2 of Pennsylvania plus most of Arizona (the Grand Canyon is spectacular!) runs about 355Mb. Don't know how that compares in size to portions of the UK you want to cover.

[Edited by - Buckeye on February 23, 2010 11:32:45 AM]