TechComm Labs

Topographic seems to be source for this common file format used by many geographic information system devices and applications. The current version has been around since 9 August 2004.

The GPX file format is a lightweight XML data format. This means it is a text file with special tags to identify a known set of fields common to GIS systems like latitude, longitude, elevation, description, and name. An example can be seen at Garmin Mass Storage Mode Devices which describes how Garmin uses the format for its GPS devices. GPSBabel describes some of the other extensions for the format.

This is the most capable and expressive of all the file formats supplied. It is described at topografix.com and is supported by EasyGPS, ExpertGPS, and many other programs described at topografix.com

GPSBabel’s reader of this module attempts to preserve tags it doesn’t really understand.

Garmin has a page that describes several of the GIS oriented file formats they support at Garmin Formats. These include AXM, Device XML, GPX, GPXX, KML, and TCX with links to the various schema definitions.

A nice history of the file format is at Travel By GPS The History of eXchanging GPs Data.

The backup is to use CSV files. These are also text but do not have explicit fields and are flat files whose data needs some interpretation. Each line is an individual record. A GPX file has defined fields made explicit and each field is of a know type. A GPX data record may be more complex than CSV formats would support.

The key issues at present is how to fill a GPX record from CSV sources and then see how the fields in the source data end up on the target device. Once that is figured out, it would be possible to figure out how to parse and clean the data source for desired results in the GPS device.

Engadget things the PND manufacturers has some competition in the new generation of cell phone devices.

As everyone knows, Garmin and TomTom have their backs against the ropes in a fight to remain relevant in an age of free GPS turn-by-turn navigation on smartphones

I don’t think it is the devices nor even the software that is providing the competition, it is the maps.

If you have a dedicated PND (personal navigation device) and want to keep its maps up to date, you are talking about spending more than $50. You can buy a current atlas at WalMart for under $10. You can use one of the many I’net mapping services for free.

Maps for the PND are like Gillette’s razor blade idea. Give away the razor and make your money on blades. The printer folks have got this idea, too, as they’ll sell printers sometimes for less than the cost of replacement toner or ink cartridges. The problem is that the cost of maps (and printer supplies) is pushing people’s idea of what is reasonable. Competition is coming from novel directions to meet the demand.

That is one area where Garmin seems to have an edge on its competition as it appears to have a more mature developer community. Worldwide routable Garmin maps from OpenStreetMap  provides a method that has the potential for providing what TomTom is doing with its user map sharing idea. Creating Custom Topo Maps for a Garmin GPS provides a means to enhance your PND maps based on government data. Then there’s  GMapToGPX which helps integrate Google Maps to Garmin PND routes.

Another consider is that this field of GPS devices and geographic information systems has a long ways to go. GPSBabel: convert, upload, download data from GPS and Map programs  has a very long list of file types used in the field that it will translate. A promising sign is that there is a trend towards XML structures with a fairly well defined set of fields.

The competition isn’t the cramming of PND capabilities into a cell phone on top of general I’net utility, it is in the maps.