Code Examples -> greatcircle.php Convert latitude/longitude coordinates between degree and decimal format. Also has ability to determine distance between them.

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PHP Code Examples

Title :	greatcircle.php Convert latitude/longitude coordinates between degree and decimal format. Also has ability to determine distance between them.
Categories :	Algorithms, PHP	Doug Pillow
Date :	Feb 27th 2003
Grade :	3 of 5 (graded 8 times)
Viewed :	24827
File :	greatcircle.php
Images :	No Images for this code example.

Search :	More code by Doug Pillow
Action :	Grade This Code Example
Tools :	My Examples List

Code

<?php
//degree format 121�8'6" degrees� minutes' seconds"
//decimal format 121.135
//accepts a coordinate in degree format and returns the equivalent decimal
//N & S are latitudes
//E & W are longitudes
//South latitudes and West longitudes are negative decimals
//calling examples
//degree2decimal('121�8�6"N'); returns 121.135
//degree2decimal('121�8�6"S'); returns -121.135
//degree2decimal('121�8�6"E'); returns 121.135
//degree2decimal('121�8�6"W'); returns -121.135
function degree2decimal($deg_coord="")
{
$dpos=strpos($deg_coord,'�');
$mpos=strpos($deg_coord,'�');
$spos=strpos($deg_coord,'"');
$mlen=(($mpos-$dpos)-1);
$slen=(($spos-$mpos)-1);
$direction=substr(strrev($deg_coord),0,1);
$degrees=substr($deg_coord,0,$dpos);
$minutes=substr($deg_coord,$dpos+1,$mlen);
$seconds=substr($deg_coord,$mpos+1,$slen);
$seconds=($seconds/60);
$minutes=($minutes+$seconds);
$minutes=($minutes/60);
$decimal=($degrees+$minutes);
//South latitudes and West longitudes need to return a negative result
if (($direction=="S") or ($direction=="W"))
        { $decimal=$decimal*(-1);}
return $decimal;
}

//accepts a coordinate in decimal format and returns the equivalent degree
//as a string
//calling examples
//decimal2degree('121.135,'LAT'); will return 121�8�6"N
//decimal2degree('-121.135,'LAT'); will return 121�8�6"S
//decimal2degree('121.135,'LON'); will return 121�8�6"E
//decimal2degree('-121.135,'LON'); will return 121�8�6"W
function decimal2degree($decimal_coord="",$latorlon="")
{
//121.135
//degrees=121
//minutes=.135*60=(8).1
//seconds=.1*60=(6)
//121�8�6"
$decpos=strpos($decimal_coord,'.');
$whole_part=substr($decimal_coord,0,$decpos);
$decimal_part=abs($decimal_coord-$whole_part);
$minutes=intval($decimal_part*60);
$seconds=intval((($decimal_part*60)-$minutes)*60);
if ($latorlon=='LAT')
        {if ($whole_part<0)
                {
                $whole_part=($whole_part*(-1));
                $L='S';
                }
        else
                {
                $L='N';
                }
        }//end if
else
        {if($latorlon=='LON')
                {if ($whole_part<0)
                        {
                        $whole_part=($whole_part*(-1));
                        $L='W';
                        }
                else
                        {
                        $L='E';
                        }
                }//end if
        }//end if
$degree=$whole_part.'�'.$minutes.'�'.$seconds.'"';
$degree.=$L;
return $degree;
}

//accepts two decimal latitude, longitude coordinates and returns the distance
//between the two
function decimal_distance($lat1="",$lon1="",$lat2="",$lon2="")
{
//$radius is determined using the following formula
//(360 degrees)*(60 minutes per degree)*(1.852) km per minute
//give a circumference of 40003.2 km
//radius is circumference/(2*pi) which gives us 6637km or 3956miles
$radius=3956;
$lat1 = deg2rad ($lat1);
$lat2 = deg2rad ($lat2);
$lon1 = deg2rad ($lon1);
$lon2 = deg2rad ($lon2);
//Haversine Formula (from R.W. Sinnott, "Virtues of the Haversine",
//Sky and Telescope, vol. 68, no. 2, 1984, p. 159):
$dlon=$lon2-$lon1;
$dlat=$lat2-$lat1;
$sinlat=sin($dlat/2);
$sinlon=sin($dlon/2);
$a=($sinlat*$sinlat)+cos($lat1)*cos($lat2)*($sinlon*$sinlon);
$c=2*asin(min(1,sqrt($a)));
$d=$radius*$c;
//
return round($d,2);
}

//accepts two degree latitude, longitude coordinates and returns the distance
//between the two
function degree_distance($lat1="",$lon1="",$lat2="",$lon2="")
{
$lat1=degree2decimal($lat1);
$lat2=degree2decimal($lat2);
$lon1=degree2decimal($lon1);
$lon2=degree2decimal($lon2);
$distance=decimal_distance($lat1,$lon1,$lat2,$lon2);
return $distance;
}

?>

See it in action at http://www.geoarmy.com/distance_calculation/

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User Comments

Daniel Boos wrote :1249
//radius is circumference/(2*pi) which gives us 6637km or 3956miles 6637km is wrong it`s ~6367km