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GEOCALC-PHP
Geographic Distance and Azimuth Calculations in PHP
Version 1.2
ABOUT THIS LIBRARY
This code was "ported" to PHP from Visual C++ by Steven Brendtro
of www.imaginerc.com. The original article and source code, written
by andyf4i can be found on CodeGuru.com at the following address:
http://www.codeguru.com/Cpp/Cpp/algorithms/article.php/c5115/
VERSION HISTORY
Version 1.0 - Initial release
Version 1.1 - Bug in getKMPerLonAtLat() fixed.
Thanks to Eric Iverson for finding it.
Version 1.2 - Bug in getLonPerKMAtLat() fixed.
FILES INCLUDED IN THIS RELEASE
GeoCalc.class.php - The actual PHP class
README - This file
ADDITIONAL PACKAGES
Also available on SourceForge.net under the GEOCALC-PHP project,
you can find a ZIP Code database (for FREE!) that you can use
for distance calculations between ZIP Codes.
For increased speed when performing distance calculations using
MySQL, be sure to check out GEOCALC-UDF at SourceForge.net.
This UDF (User Defined Function) is designed for MySQL and has
been known to reduce query time up to 1000%!
METHODS
# Basic Methods:
GeoCalc(); # Default Constructor
GCDistance($lat1, $lon1, $lat2, $lon2);
# Using the Great Circle formula, calculate
# the distance in kilometers between
# Latitude/Longitude 1 and Latitude/Longitude 2
GCAzimuth($lat1, $lon1, $lat2, $lon2);
# Using the Great Circle formula, calculate the
# azimuth between Latitude/Longitude 1 and
# Latitude/Longitude 2
ApproxDistance($lat1, $lon1, $lat2, $lon2);
# Using the Ellipsoidal Approximation formula,
# calculate the distance in kilometers between
# Latitude/Longitude 1 and Latitude/Longitude 2
EllipsoidDistance($lat1, $lon1, $lat2, $lon2);
# Using the Ellipsoidal Distance formula, calculate
# the distance in kilometers between Latitude/Longitude 1
# and Latitude/Longitude 2. This formula is the most
# accurate of the formulas.
# Helper Methods
getKmPerLonAtLat($dLatitude);
# Get the number of Kilometers per degree longitude
# at the given latitude.
getLonPerKmAtLat($dLatitude);
# Get the number of degrees longitude per kilometer at the
# given latitude.
getKmPerLat();
# Get the number of kilometers per degree latitude (average
# of 111.0 kilometers per degree)
getLatPerKm();
# Get the number of degrees latitude per kilometer (average
# of 1/111 degrees per kilometer)
# Helper Function (not a method in the class, but a function)
ConvKilometersToMiles($dValue);
# Convert a distance from kilometers to miles
# (km / 1.609344 = miles).
EXAMPLES
Here are some example uses for this class:
include_once("GeoCalc.class.php");
$oGC = new GeoCalc();
// Great Circle Distance
$dDist = $oGC->GCDistance(38.9333,-94.3253,38.9314,-94.4876);
// Great Circle Azimuth
$dDist = $oGC->GCAzimuth(38.9333,-94.3253,38.9314,-94.4876);
// Approximate Ellipsoid Distance
$dDist = $oGC->ApproxDistance(38.9333,-94.3253,38.9314,-94.4876);
// Accurate Ellipsoid Distance
$dDist = $oGC->EllipsoidDistance(38.9333,-94.3253,38.9314,-94.4876);
// Convert distance from kilometers to miles
$dDistMiles = ConvKilometersToMiles($dDist);
// Advanced Calculation:
// The following will search for ZIP codes
// within a radius (roughly calculated)
// Define the center of the search bounds...
$dLongitude = -94.44590241;
$dLatitude = 38.7996;
// Define the maximum search distance
$dRadius = 100.00; // in kilometers
// Calculate the boundary distance in degrees longitude / latitude
$dAddLat = $oGC->getLatPerKm() * $dRadius;
$dAddLon = $oGC->getLonPerKmAtLat($dLatitude) * $dRadius;
// Calculate the boundaries
$dNorthBounds = $dLatitude + $dAddLat;
$dSouthBounds = $dLatitude - $dAddLat;
$dWestBounds = $dLongitude - $dAddLon;
$dEastBounds = $dLongitude + $dAddLon;
print "Center Longitude: $dLongitude\n";
print "Center Latitude: $dLatitude\n";
print "Radius: $dRadius kilometers\n";
print "North Bounds: $dNorthBounds\n";
print "South Bounds: $dSouthBounds\n";
print "East Bounds: $dEastBounds\n";
print "West Bounds: $dWestBounds\n";
// Sample SQL query stament based on above boundaries:
$strQuery = "SELECT * FROM PostalCodes " .
"WHERE Latitude > $dSouthBounds " .
"AND Latitude < $dNorthBounds " .
"AND Longitude > $dWestBounds " .
"AND Longitude < $dEastBounds";
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