README

GPX Utils

A set of utilities to operate on GPX files and sets of GPX files.

Reading GPX Files

The GPX reader class DerickR/GPX/Reader can be used to read a GPX file.

It can read GPX routes (rte/rtept) and if none are present, it will read a GPX track (trk/trkseg/trkpt) instead.

You can read a GPX file with:

<?php
require __DIR__ . '/vendor/autoload.php';

use DerickR\GPX\Reader;

$gpxInformation = new Reader( $file );
?>

To access the tracks, you can use the getTrack() method which returns a DerickR/GPX/Track object, which encapsulates a ordered set of coordinate pairs. If the GPX file had multiple tracks, these are merged into one:

$track = $gpxInformation->getTrack();

To get individual tracks out of a GPX file, you can use the getTracks() method to obtain an array of Track objects:

$tracks = $gpxInformation->getTracks();
foreach ( $tracks as $track )
{
        /* Do something with $track */
}

For GPX files that contain routes (rte/rtept) this will still return a merged track.

For GPX files that contain tracks (trk/trkseg) this return an array of tracks, with each Track object representing a track as stored in the GPX file.

To merge tracks stored in multiple GPX files, see Merging GPX Files.

Writing GPX Files

The GPX writer class DerickR/GPX/Writer can be used to write a Track object as a GPX track using trk/trkseg/trkpt elements. It only supports the lat and lon XML elements.

You can write a track to GPX file with:

<?php
require __DIR__ . '/vendor/autoload.php';

use DerickR\GPX\Writer;

$writer = new Writer( $track );
$writer->writeGpx( 'route-test.gpx' );
?>

Instead of writing GPX XML directly to a file, it is also possible to retrieve a string with this information, by using the getGpxString() method:

<?php
require __DIR__ . '/vendor/autoload.php';

use DerickR\GPX\Writer;

$writer = new Writer( $track );
$xmlString = $writer->getGpxString();
?>

Operating on Tracks

The Track class has several methods to operate on GPX tracks. The following methods are supported:

getTrackData: Returns an array with lat/lon coordinate pairs.
getFirstPointAsGeoJson: Returns the first element in the track as a GeoJson formatted array.
getLastPointAsGeoJson: Returns the last element in the track as a GeoJson formatted array.
appendTrack( Track $newTrack ): Adds all the coordinate pairs from $newTrack in sequence to the track.
reverse(): Reverses the array of coordinate pairs that make up the track.
truncatePrecision( int $decimals ): Loops over all the coordinate pairs in the track, and truncates the number of decimals in the coordinate pair to $decimals. In a second loop, it merges two consecutive coordinate pairs if they are the same after truncation.

Merging GPX Files

The Utils::createMergedTrack static method can be used to combine a set of GPX files. The method automatically reverses and selects the order in which the tracks are merged, based on the first and last points in the track.

The second argument to createMergedTrack determines how far (in metres) the different points of different tracks might lay away from each other to be considered as consecutive. By default, this is 25.0 metres.

If the GPX files are not consecutive then an Exception in thrown.

For example to merge all GPX files in a directory, you would use:

<?php
require __DIR__ . '/vendor/autoload.php';

use DerickR\GPX\Reader;
use DerickR\GPX\Utils;
use DerickR\GPX\Writer;

// Find all .gpx files
$files = glob( '*.gpx' );

// Read all tracks into an array
$tracks = [];
foreach ( $files as $file )
{
        $tracks[] = (new Reader( $file ))->getTrack();
}

// Merge all tracks into a single one.
$track = Utils::createMergedTrack( $tracks );

// Write created track to a file
$writer = new Writer( $track );
$writer->writeGpx( 'route-test.gpx' );
?>

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