| 1 |
<?php
|
| 2 |
// $Id: earth.inc,v 1.9 2008/01/24 09:29:47 bdragon Exp $
|
| 3 |
|
| 4 |
/**
|
| 5 |
* License clarification:
|
| 6 |
*
|
| 7 |
* On Feb 13, 2005, in message <Pine.LNX.4.58.0502131827510.5072@server1.LFW.org>,
|
| 8 |
* the creator of these routines, Ka-Ping Yee, authorized these routines to be
|
| 9 |
* distributed under the GPL.
|
| 10 |
*/
|
| 11 |
|
| 12 |
/**
|
| 13 |
* @file
|
| 14 |
* Trigonometry for calculating geographical distances.
|
| 15 |
* All function arguments and return values measure distances in metres
|
| 16 |
* and angles in degrees. The ellipsoid model is from the WGS-84 datum.
|
| 17 |
* Ka-Ping Yee, 2003-08-11
|
| 18 |
*/
|
| 19 |
|
| 20 |
//$earth_radius_semimajor = 6378137.0;
|
| 21 |
//$earth_flattening = 1/298.257223563;
|
| 22 |
//$earth_radius_semiminor = $earth_radius_semimajor * (1 - $earth_flattening);
|
| 23 |
//$earth_eccentricity_sq = 2*$earth_flattening - pow($earth_flattening, 2);
|
| 24 |
|
| 25 |
// I don't know what's up: PHP is hating on my global variables (commented out above),
|
| 26 |
// so I have to write functions that return them! (-Ankur)
|
| 27 |
// Commenting out the global variables above and replacing them with functions that
|
| 28 |
// return the same values is the only thing I changed since, for some reason, my
|
| 29 |
// PHP wasn't acknowledging these global variables.
|
| 30 |
// This library is an original implementation of UCB CS graduate student, Ka-Ping Yee (http://www.zesty.ca).
|
| 31 |
|
| 32 |
function earth_radius_semimajor() {
|
| 33 |
return 6378137.0;
|
| 34 |
}
|
| 35 |
|
| 36 |
function earth_flattening() {
|
| 37 |
return (1/298.257223563);
|
| 38 |
}
|
| 39 |
|
| 40 |
function earth_radius_semiminor() {
|
| 41 |
return (earth_radius_semimajor() * (1 - earth_flattening()));
|
| 42 |
}
|
| 43 |
|
| 44 |
function earth_eccentricity_sq() {
|
| 45 |
return (2*earth_flattening() - pow(earth_flattening(), 2));
|
| 46 |
}
|
| 47 |
|
| 48 |
// Latitudes in all of U. S.: from -7.2 (American Samoa) to 70.5 (Alaska).
|
| 49 |
// Latitudes in continental U. S.: from 24.6 (Florida) to 49.0 (Washington).
|
| 50 |
// Average latitude of all U. S. zipcodes: 37.9.
|
| 51 |
|
| 52 |
function earth_radius($latitude=37.9) {
|
| 53 |
//global $earth_radius_semimajor, $earth_radius_semiminor;
|
| 54 |
// Estimate the Earth's radius at a given latitude.
|
| 55 |
// Default to an approximate average radius for the United States.
|
| 56 |
|
| 57 |
$lat = deg2rad($latitude);
|
| 58 |
|
| 59 |
$x = cos($lat)/earth_radius_semimajor();
|
| 60 |
$y = sin($lat)/earth_radius_semiminor();
|
| 61 |
return 1 / (sqrt($x*$x + $y*$y));
|
| 62 |
}
|
| 63 |
|
| 64 |
function earth_xyz($longitude, $latitude, $height = 0) {
|
| 65 |
// Convert longitude and latitude to earth-centered earth-fixed coordinates.
|
| 66 |
// X axis is 0 long, 0 lat; Y axis is 90 deg E; Z axis is north pole.
|
| 67 |
//global $earth_radius_semimajor, $earth_eccentricity_sq;
|
| 68 |
$long = deg2rad($longitude);
|
| 69 |
$lat = deg2rad($latitude);
|
| 70 |
|
| 71 |
$coslong = cos($long);
|
| 72 |
$coslat = cos($lat);
|
| 73 |
$sinlong = sin($long);
|
| 74 |
$sinlat = sin($lat);
|
| 75 |
$radius = earth_radius_semimajor() /
|
| 76 |
sqrt(1 - earth_eccentricity_sq() * $sinlat * $sinlat);
|
| 77 |
$x = ($radius + $height) * $coslat * $coslong;
|
| 78 |
$y = ($radius + $height) * $coslat * $sinlong;
|
| 79 |
$z = ($radius * (1 - earth_eccentricity_sq()) + $height) * $sinlat;
|
| 80 |
return array($x, $y, $z);
|
| 81 |
}
|
| 82 |
|
| 83 |
function earth_arclength($angle, $latitude=37.9) {
|
| 84 |
// Convert a given angle to earth-surface distance.
|
| 85 |
return deg2rad($angle) * earth_radius($latitude);
|
| 86 |
}
|
| 87 |
|
| 88 |
function earth_distance($longitude1, $latitude1, $longitude2, $latitude2) {
|
| 89 |
// Estimate the earth-surface distance between two locations.
|
| 90 |
$long1 = deg2rad($longitude1);
|
| 91 |
$lat1 = deg2rad($latitude1);
|
| 92 |
$long2 = deg2rad($longitude2);
|
| 93 |
$lat2 = deg2rad($latitude2);
|
| 94 |
$radius = earth_radius(($latitude1 + $latitude2) / 2);
|
| 95 |
|
| 96 |
$cosangle = cos($lat1)*cos($lat2) *
|
| 97 |
(cos($long1)*cos($long2) + sin($long1)*sin($long2)) +
|
| 98 |
sin($lat1)*sin($lat2);
|
| 99 |
return acos($cosangle) * $radius;
|
| 100 |
}
|
| 101 |
|
| 102 |
/*
|
| 103 |
* Returns the SQL fragment needed to add a column called 'distance'
|
| 104 |
* to a query that includes the location table
|
| 105 |
*
|
| 106 |
* @param $longitude The measurement point
|
| 107 |
* @param $latibude The measurement point
|
| 108 |
* @param $tbl_alias If necessary, the alias name of the location table to work from. Only required when working with named {location} tables
|
| 109 |
*/
|
| 110 |
function earth_distance_sql($longitude, $latitude, $tbl_alias = '') {
|
| 111 |
// Make a SQL expression that estimates the distance to the given location.
|
| 112 |
$long = deg2rad($longitude);
|
| 113 |
$lat = deg2rad($latitude);
|
| 114 |
$radius = earth_radius($latitude);
|
| 115 |
|
| 116 |
// If the table alias is specified, add on the separator.
|
| 117 |
$tbl_alias = empty($tbl_alias) ? $tbl_alias : ($tbl_alias .'.');
|
| 118 |
|
| 119 |
$coslong = cos($long);
|
| 120 |
$coslat = cos($lat);
|
| 121 |
$sinlong = sin($long);
|
| 122 |
$sinlat = sin($lat);
|
| 123 |
return "(IFNULL(ACOS($coslat*COS(RADIANS({$tbl_alias}latitude))*($coslong*COS(RADIANS({$tbl_alias}longitude)) + $sinlong*SIN(RADIANS({$tbl_alias}longitude))) + $sinlat*SIN(RADIANS({$tbl_alias}latitude))), 0.00000)*$radius)";
|
| 124 |
}
|
| 125 |
|
| 126 |
function earth_longitude_range($longitude, $latitude, $distance) {
|
| 127 |
// Estimate the min and max longitudes within $distance of a given location.
|
| 128 |
$long = deg2rad($longitude);
|
| 129 |
$lat = deg2rad($latitude);
|
| 130 |
$radius = earth_radius($latitude);
|
| 131 |
|
| 132 |
$angle = $distance / $radius;
|
| 133 |
$diff = asin(sin($angle)/cos($lat));
|
| 134 |
$minlong = $long - $diff;
|
| 135 |
$maxlong = $long + $diff;
|
| 136 |
if ($minlong < -pi()) { $minlong = $minlong + pi()*2; }
|
| 137 |
if ($maxlong > pi()) { $maxlong = $maxlong - pi()*2; }
|
| 138 |
return array(rad2deg($minlong), rad2deg($maxlong));
|
| 139 |
}
|
| 140 |
|
| 141 |
function earth_latitude_range($longitude, $latitude, $distance) {
|
| 142 |
// Estimate the min and max latitudes within $distance of a given location.
|
| 143 |
$long = deg2rad($longitude);
|
| 144 |
$lat = deg2rad($latitude);
|
| 145 |
$radius = earth_radius($latitude);
|
| 146 |
|
| 147 |
$angle = $distance / $radius;
|
| 148 |
$minlat = $lat - $angle;
|
| 149 |
$maxlat = $lat + $angle;
|
| 150 |
$rightangle = pi()/2;
|
| 151 |
if ($minlat < -$rightangle) { // wrapped around the south pole
|
| 152 |
$overshoot = -$minlat - $rightangle;
|
| 153 |
$minlat = -$rightangle + $overshoot;
|
| 154 |
if ($minlat > $maxlat) { $maxlat = $minlat; }
|
| 155 |
$minlat = -$rightangle;
|
| 156 |
}
|
| 157 |
if ($maxlat > $rightangle) { // wrapped around the north pole
|
| 158 |
$overshoot = $maxlat - $rightangle;
|
| 159 |
$maxlat = $rightangle - $overshoot;
|
| 160 |
if ($maxlat < $minlat) { $minlat = $maxlat; }
|
| 161 |
$maxlat = $rightangle;
|
| 162 |
}
|
| 163 |
return array(rad2deg($minlat), rad2deg($maxlat));
|
| 164 |
}
|
Parent Directory
| 
Revision Log
| 
Revision Graph