
== CONFIG/elev ==

This directory contains ground elevation maps, used for more accurate rendering
of taxiing and landing AI traffic in the viewers. There may be one file per
location (ICAO.elev), which is loaded on session start.

An elevation map file must contain a header line with the coordinates of the NW
and SE corners of the covered zone. The lines immediately following the header
are elevation plots in feet AMSL, distributed as equally spaced in both
dimensions over the zone. So the more values provided, the finer the precision.
These lines must all have the same number of values. Elevation in one point is
then retrieved via a bilinear interpolation between the four closest values.

For example:
37.6311,-122.3965  37.6096,-122.3564
	1.1  2.2  .22
	.98  3.1  2.5

Line comments, starting with '#', are allowed anywhere in the file.

NB: If you have "fgelev" (a tool that comes with any FlightGear installation),
you can use the provided "mkElevMap.py" script. It will generate a map in the
"OUTPUT" directory, given corner coordinates and a precision value.

When no elevation map is found for an airfield, the elevation value is used
everywhere on the ground. This should be OK for a rough approximation on flat
terrain, but ground traffic will not follow any slopes, thus may appear to be
floating above the ground, or dipping into it.

