Google Maps Polyline Encoding Tool

A simple PHP class for translating polyline into an encoded strings for Google Maps.

Install

Use composer.

$ curl -sS https://getcomposer.org/installer | php
$ cat > composer.json <<EOF
{
   "require": {
      "emcconville/google-map-polyline-encoding-tool" : ">=1.2.1"
   }
}
EOF
$ php composer.phar install

Old fashion way.

$ git clone git://github.com/emcconville/google-map-polyline-encoding-tool.git
$ cp src/Polyline.php /path/to/your/application/includes/Polyline.php

Usage

Encoding

// Points to encode
$points = array(
        array(41.89084,-87.62386),
        array(41.89086,-87.62279),
        array(41.89028,-87.62277),
        array(41.89028,-87.62385),
        array(41.89084,-87.62386)
    );

$encoded = Polyline::encode($points);
//=> wxt~Fd`yuOCuErBC?vEoB@

Decoding

// String to decode
$encoded = "kiw~FpoavObBA?fAzEC";

$points = Polyline::decode($encoded);
//=> array(
//     41.90374,-87.66729,41.90324,-87.66728,
//     41.90324,-87.66764,41.90214,-87.66762
//   );

// Or list of tuples
$points = Polyline::pair($points);
//=> array(
//     array(41.90374,-87.66729),
//     array(41.90324,-87.66728),
//     array(41.90324,-87.66764),
//     array(41.90214,-87.66762)
//   );

Examples

See examples directory for creative ideas, and please contribute new use-cases / hacks.

• Well-Known Binary converter.
• Preview encoded strings with a SVG transcoder.

Specify precision

Precision defaults to 1e-5 (0.00001) which is expected by Google Map API. Other API's like OSRM expect a precision of 1e-6. You can adjust the precision you want by sub-classing Polyline, and overwrite the $precision static property.

class PolylineOSRM extends Polyline
{
    protected static $precision = 6;
}
$points = PolylineOSRM::decode($line);
$line = PolylineOSRM::encode($points);

Caution

• Adjusting the precision level will not guarantee improved accuracy. Existing issues with PHP's internal float point arithmetic can contribute accuracy issues.
• Third party libraries will not automatically know what level of precision was used during encoding.

Family

This library exists as a PHP reference point for Google's Encoded Polyline Algorithm Format. There is also a C implementation, and a namespace/trait library under active development.