88 lines
2.6 KiB
Perl
Executable file
88 lines
2.6 KiB
Perl
Executable file
#!/usr/bin/perl
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#
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# Written by Curtis L. Olson, started January 2003
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#
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# This file is in the Public Domain and comes with no warranty.
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#
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# $Id$
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# ----------------------------------------------------------------------------
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# This script will calculate the flightgear ground elevation for a
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# serious of lon/lat pairs, given one per line via stdin. Result it
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# written to stdout. Lon/lat must be specified in decimal degrees,
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# i.e. "-110.2324 39.872"
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#
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# This requires a copy of flightgear running with "--fdm=null" on the
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# specified "$server" host name, at the specified "$port".
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#
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# I highly recommend that you if you plan to feed a large number of
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# coordinates through this script that you presort your list by tile id #
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# That will minimize the load on the FG tile pager since you will process
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# all coordinates for a particular tile before moving on to the next.
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# Also, there is a chance the next tile will already be loaded if it is near
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# the previous (which it will tend to be if you sort by tile id.)
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use strict;
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use Time::HiRes qw( usleep );
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require "telnet.pl";
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my( $server ) = "localhost";
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my( $port ) = 5401;
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my( $timeout ) = 10;
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# open the connection to the running copy of flightgear
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my( $fgfs );
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if ( !( $fgfs = &connect($server, $port, $timeout) ) ) {
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die "Error: can't open socket\n";
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}
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&send( $fgfs, "data" ); # switch to raw data mode
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# elevate ourselves only to make the view more interesting, this
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# doesn't affect the results
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set_prop( $fgfs, "/position/altitude-ft", "5000" );
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my( $last_lon ) = -1000.0;
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my( $last_lat ) = -1000.0;
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my( $last_elev ) = -1000.0;
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# iterate through the requested coordinates
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while ( <> ) {
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my( $lon, $lat ) = split;
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set_prop( $fgfs, "/position/longitude-deg", $lon );
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set_prop( $fgfs, "/position/latitude-deg", $lat );
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# wait 1 second for scenery to load
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usleep(500000);
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# then fetch ground elevation
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my( $elev ) = get_prop( $fgfs, "/position/ground-elev-m" );
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if ( $lon != $last_lon || $lat != $last_lat ) {
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my($waitcount) = 0;
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while ( $elev == $last_elev && $waitcount < 5 ) {
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print "(WARNING: waiting an addition 1 second and requerying.)\n";
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# same answer as last time, scenery is probably still loading,
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# let's wait 1 more seconds and hope we get it right the next
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# time, we bail after 5 seconds.
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usleep(1000000);
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$elev = get_prop( $fgfs, "/position/ground-elev-m" );
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$waitcount++;
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}
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}
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print "$lon $lat $elev\n";
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$last_elev = $elev;
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$last_lon = $lon;
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$last_lat = $lat;
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}
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# shutdown our connection (this leaves FG running)
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&send( $fgfs, "quit");
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close $fgfs;
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