Kami - 1 year ago 206

PHP Question

I would like to extract the GPS EXIF tag from pictures using php.

I'm using the

`exif_read_data()`

`GPS.GPSLatitudeRef: N`

GPS.GPSLatitude:Array ( [0] => 46/1 [1] => 5403/100 [2] => 0/1 )

GPS.GPSLongitudeRef: E

GPS.GPSLongitude:Array ( [0] => 7/1 [1] => 880/100 [2] => 0/1 )

GPS.GPSAltitudeRef:

GPS.GPSAltitude: 634/1

I don't know how to interpret 46/1 5403/100 and 0/1 ? 46 might be 46° but what about the rest especially 0/1 ?

`angle/1 5403/100 0/1`

What is this structure about ?

How to convert them to "standard" ones (like 46°56′48″N 7°26′39″E from wikipedia) ? I would like to pass thoses coordinates to the google maps api to display the pictures positions on a map !

Answer Source

According to http://en.wikipedia.org/wiki/Geotagging, `( [0] => 46/1 [1] => 5403/100 [2] => 0/1 )`

should mean 46/1 degrees, 5403/100 minutes, 0/1 seconds, i.e. 46°54.03′0″N. Normalizing the seconds gives 46°54′1.8″N.

This code below should work, as long as you don't get negative coordinates (given that you get N/S and E/W as a separate coordinate, you shouldn't ever have negative coordinates). Let me know if there is a bug (I don't have a PHP environment handy at the moment).

```
//Pass in GPS.GPSLatitude or GPS.GPSLongitude or something in that format
function getGps($exifCoord)
{
$degrees = count($exifCoord) > 0 ? gps2Num($exifCoord[0]) : 0;
$minutes = count($exifCoord) > 1 ? gps2Num($exifCoord[1]) : 0;
$seconds = count($exifCoord) > 2 ? gps2Num($exifCoord[2]) : 0;
//normalize
$minutes += 60 * ($degrees - floor($degrees));
$degrees = floor($degrees);
$seconds += 60 * ($minutes - floor($minutes));
$minutes = floor($minutes);
//extra normalization, probably not necessary unless you get weird data
if($seconds >= 60)
{
$minutes += floor($seconds/60.0);
$seconds -= 60*floor($seconds/60.0);
}
if($minutes >= 60)
{
$degrees += floor($minutes/60.0);
$minutes -= 60*floor($minutes/60.0);
}
return array('degrees' => $degrees, 'minutes' => $minutes, 'seconds' => $seconds);
}
function gps2Num($coordPart)
{
$parts = explode('/', $coordPart);
if(count($parts) <= 0)// jic
return 0;
if(count($parts) == 1)
return $parts[0];
return floatval($parts[0]) / floatval($parts[1]);
}
```