A bad day for measurements

Here are the results of another try at comparing GPS track logs – in particular the elevation profiles – between different devices and applications.

elevation profiles
elevation profiles

The weather was fine, if a bit cold with gusty winds. The hike was mostly in open terrain or on wide forest tracks. Less than an estimated 20 % of the track was under forest cover. The devices and apps are :

  • Garmin GPSMap 64s
  • Android Smartphone with Ultra GPS Logger
  • Android smartphone with Orux Maps

For comparison, the chart includes the theoretical distance/elevation graph as obtained by creating the gpx using a PC based tracing tool.

What to conclude ?
Garmin stays closest to the theoretical track. In fact, it is almost dead on. Towards the 5 km mark we deviated from the theoretical track to walk about 50 m out and back to view an aven (cavern opening in flat limestone terrain). This put a distance lag into the Garmin profile. Meanwhile the 2 smartphone apps were busily overestimating distances (Ultra-gps-logger by about 1.5 km and Orux by over 3 km ! Allowing for the overestimated distance, if you mentally squeeze the Orux profile proportionally back to 9.5 km, you can see that the elevation profile seems to move in sync with the theoretical values and might be close to the mark. Ultra-GPS-Logger on the other hand continuously overshoots altitudes by 50 to 60 m. In conclusion, a bad day for smartphone apps.

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