GPX Gem

Copyright (C) 2006 Doug Fales doug@falesafeconsulting.com

What It Does

This library reads GPX files and provides an API for reading and manipulating the data as objects. For more info on the GPX format, see http://www.topografix.com/gpx.asp.

In addition to parsing GPX files, this library is capable of converting Magellan NMEA files to GPX, and writing new GPX files. It can crop and delete rectangular areas within a file, and it also calculates some meta-data about the tracks and points in a file (such as distance, duration, average speed, etc).

Examples

Reading a GPX file, and cropping its contents to a given area:

gpx =  GPX::GPXFile.new(:gpx_file => filename)   # Read GPX file
bounds = GPX::Bounds.new(params)                 # Create a rectangular area to crop
gpx.crop(bounds)                                 # Crop it
gpx.write(filename)                              # Save it

Converting a Magellan track log to GPX:

if GPX::MagellanTrackLog::is_magellan_file?(filename)
 GPX::MagellanTrackLog::convert_to_gpx(filename, "#{filename}.gpx")
end

Exporting an ActiveRecord to GPXFile (as Waypoints)

#
# Our active record in this example is called stop
#
 
# models/stop.rb 
class Stop < ActiveRecord::Base
   # This model has the following attributes:
   # name
   # lat
   # lon
   # updated_at
   
   def self.to_gpx
     require 'GPX'
     gpx = GPX::GPXFile.new
     all.each do |stop|
       gpx.waypoints << GPX::Waypoint.new({name: stop.name, lat: stop.lat, lon: stop.lon, time: stop.updated_at})
     end 
     gpx.to_s
   end
 end # class


# controllers/stops.rb
def index 
   @stops = Stop.all
   respond_to do |format|
    format.html {render :index}
    format.gpx { send_data @stops.to_gpx, filename: controller_name + '.gpx' }
   end
end


# Add this line to config/initializers/mime_types.rb
Mime::Type.register "application/gpx+xml", :gpx
  
 
# To get the xml file:
#   http://localhost:3000/stops.gpx

You have a complete example on how to create a gpx file from scratch on tests/output_text.rb.

Notes

This library was written to bridge the gap between my Garmin Geko and my website, WalkingBoss.org (RIP). For that reason, it has always been more of a work-in-progress than an attempt at full GPX compliance. The track side of the library has seen much more use than the route/waypoint side, so if you're doing something with routes or waypoints, you may need to tweak some things.

Since this code uses XML to read an entire GPX file into memory, it is not the fastest possible solution for working with GPX data, especially if you are working with tracks from several days or weeks.

Finally, it should be noted that none of the distance/speed calculation or crop/delete code has been tested under International Date Line-crossing conditions. That particular part of the code will likely be unreliable if you're zig-zagging across 180 degrees longitude routinely.