fly/flightgear
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Simple perl script for calculating a tile path based on lon/lat. Does

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not depend on SimGear, but doesn't handle objects right on the poles
either.
This commit is contained in:
david 2002-09-22 15:52:46 +00:00
parent 743b4848cf
commit 3b3102d7c8
1 changed files with 159 additions and 0 deletions
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scripts/perl/scenery/calc-tile.pl Normal file
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#!/usr/bin/perl -w
########################################################################
# calc-tile.pl
#
# Synopsis: Calculate a FlightGear tile base on longitude and latitude.
# Usage: perl calc-tile.pl <lon> <lat>
########################################################################
use strict;
use POSIX;
########################################################################
# Constants.
########################################################################
my $EPSILON = 0.0000001;
my $DIRSEP = '/';
########################################################################
# Functions.
########################################################################
#
# Calculate the number of columns of tiles in a degree of longitude.
#
sub bucket_span {
my ($lat) = (@_);
if ($lat>= 89.0 ) {
return 360.0;
} elsif ($lat>= 88.0 ) {
return 8.0;
} elsif ($lat>= 86.0 ) {
return 4.0;
} elsif ($lat>= 83.0 ) {
return 2.0;
} elsif ($lat>= 76.0 ) {
return 1.0;
} elsif ($lat>= 62.0 ) {
return 0.5;
} elsif ($lat>= 22.0 ) {
return 0.25;
} elsif ($lat>= -22.0 ) {
return 0.125;
} elsif ($lat>= -62.0 ) {
return 0.25;
} elsif ($lat>= -76.0 ) {
return 0.5;
} elsif ($lat>= -83.0 ) {
return 1.0;
} elsif ($lat>= -86.0 ) {
return 2.0;
} elsif ($lat>= -88.0 ) {
return 4.0;
} elsif ($lat>= -89.0 ) {
return 8.0;
} else {
return 360.0;
}
}
#
# Format longitude as e/w.
#
sub format_lon {
my ($lon) = (@_);
if ($lon < 0) {
return sprintf("w%03d", int(0-$lon));
} else {
return sprintf("e%03d", int($lon));
}
}
#
# Format latitude as n/s.
#
sub format_lat {
my ($lat) = (@_);
if ($lat < 0) {
return sprintf("s%02d", int(0-$lat));
} else {
return sprintf("n%02d", int($lat));
}
}
#
# Generate the directory name for a location.
#
sub directory_name {
my ($lon, $lat) = (@_);
my $lon_floor = POSIX::floor($lon);
my $lat_floor = POSIX::floor($lat);
my $lon_chunk = POSIX::floor($lon/10.0) * 10;
my $lat_chunk = POSIX::floor($lat/10.0) * 10;
return format_lon($lon_chunk) . format_lat($lat_chunk) . $DIRSEP
. format_lon($lon_floor) . format_lat($lat_floor);
}
#
# Generate the tile index for a location.
#
sub tile_index {
my ($lon, $lat) = (@_);
my $lon_floor = POSIX::floor($lon);
my $lat_floor = POSIX::floor($lat);
my $span = bucket_span($lat);
my $x;
if ($span < $EPSILON) {
$lon = 0;
$x = 0;
} elsif ($span <= 1.0) {
$x = int(($lon - $lon_floor) / $span);
} else {
if ($lon >= 0) {
$lon = int(int($lon/$span) * $span);
} else {
$lon = int(int(($lon+1)/$span) * $span - $span);
if ($lon < -180) {
$lon = -180;
}
}
$x = 0;
}
my $y;
$y = int(($lat - $lat_floor) * 8);
my $index = 0;
$index += ($lon_floor + 180) << 14;
$index += ($lat_floor + 90) << 6;
$index += $y << 3;
$index += $x;
return $index;
}
########################################################################
# Main program.
########################################################################
my ($lon, $lat) = (@ARGV);
my $dir = directory_name($lon, $lat);
my $index = tile_index($lon, $lat);
my $path = "$dir$DIRSEP$index.stg";
print "Longitude: $lon\n";
print "Latitude: $lat\n";
print "Tile: $index\n";
print "Path: \"$path\"\n";
1;