fgelev - Compute FlightGear scenery elevation for a given list of points
fgelev [--expire num] [--print-solidness]
[--fg-root rootdir] [--fg-scenery scenerydir]
fgelev is a standalone utility that, given a list of points on standard
input, prints the corresponding elevation for each of them on standard output.
It can also (optionally) print whether the material covering that point is
solid or not.
The list of points must be in the following form:
id lon lat
where id is an arbitrary identifier for the point,
lon is the longitude of the point and lat is the latitude of
the point. Positive longitudes (latitudes) correspond to points located in
the Eastern (Northern) hemisphere; negative ones correspond to points
located in the Western (Southern) hemisphere.
The list of elevations returned by fgelev is in the
id: elev solid
where id is the identifier of the point passed as input,
elev is the elevation of the point in meters (or -1000 if the
elevation of the given point was not found) and solid is:
- the string solid if the parameter --print-solidness was
passed to fgelev and the material covering the point is solid;
- the string - if the parameter --print-solidness was passed
to fgelev and the material covering the point is not solid;
- absent if the parameter --print-solidness was not passed to
fgelev exits with EXIT_SUCCESS on success, with
EXIT_FAILURE if it is unable to read data from standard input or to
load the scenery.
- --expire num
- To speed up elevation data retrieval, fgelev uses an internal
cache. This option lets the user specify the number of requests after
which, if a point was not queried in them, it should be marked as expired.
By default, fgelev expires points not queried in the last 10
- Require fgelev to print the solidness of the material covering the
queried point. See the DESCRIPTION section for more details.
- --fg-root rootdir
- Set the FlightGear data root directory ($FG_ROOT) to
rootdir. If this option is not set, fgelev uses the path
specified in the FG_ROOT environment variable or, absent that, the
FlightGear data directory chosen at the time the program was
- --fg-scenery scenerydir
- Set the FlightGear scenery directory ($FG_SCENERY) to
scenerydir. If this option is not set, fgelev uses the path
specified in the FG_SCENERY environment variable or, absent that,
the Scenery subdirectory inside $FG_ROOT.
- If FG_ROOT is set and --fg-root is not set, it specifies the
root data directory to use.
- If FG_SCENERY is set and --fg-scenery is not set, it
specifies the scenery directory to use.