Self-Hosted GPS Tracker

With my T-Beam GPS Tracker operating fine during car trips, I finally have a secure replacement for this very old GPS Tracker App on my nine years old HTC Desire HD*.

The TTGO T-Beam came in this box. I only had to drill a small hole for the antenna

 

The concept of the old Android app (meanwhile removed from both the App Store and github by its creator**) is very simple. It periodically sends your phone’s GPS readings as http GET parameters to a self-hosted endpoint of your choice. Since TheThingsNetwork‘s HTTP Integration works more or less the same, I could simply reuse the php backend that I once wrote for the app, now for showing my LoRaWan tracker’s location on a map.

(zoomed out for privacy reasons)

 

Data flow is as follows:

  • Tracker periodically sends GPS readings to TheThingsNetwork. The sketch makes the interval between consecutive send commands depend on the last GPS speed reading
  • HTTP Integration service sends LoRaWan payload+metadata in an http POST variable to a php script (dump.php) on my server (see below)
  • dump.php appends the entire POST value to a log file (log.txt) and writes a formatted selection of relevant data to a text file (last_reading.txt, always overwritten)

The map is an embedded OpenStreetMap ‘Leaflet’ inside an html file, with some simple javacript periodically reading the formatted data from last_reading.txt. After extracting the individual GPS readings and a timestamp in the background, these values are used to update the tracker’s location on the map and to refresh textual info.

Data in the logfile can, if necessary after conversion, be used for analyzing and drawing the trackers’s route. There are several standard solutions for this, even online.

 

*Running non-stop on its original battery and without any problems since March 2011. I ❤ HTC!

**Hervé Renault, who suggests a modern alternative on his personal website (in French)


My dump.php file (presumes fields latitude, longitude, speed and sats in TTN payload):