labroides
 Captain
Flight distance : 9991457 ft
Australia
Offline
|
GPS is really bad for alittude accuracy.
It's not just bad, it swings all over the place +/- 200 feet is common.
DJI putting the GPS altitude in the normal place in Exif and moving the more accurate barometric altitude somewhere else a few firmware versions ago was a mistake.
DJI know how bad GPS is for altitude ... they don't use it for flying.
Here's what Garmin say to explain the problem with GPS altitude accuracy.
How accurate is the GPS elevation reading?
GPS heights are based on an ellipsoid (a mathematical representation of the earth's shape), while USGS map elevations are based on a vertical datum tied to the geoid (or what is commonly called mean sea level). Basically, these are two different systems, although they have a relationship that has been modeled.
The main source of error has to do with the arrangement of the satellite configurations during fix determinations. The earth blocks out satellites needed to get a good quality vertical measurement. Once the vertical datum is taken into account, the accuracy permitted by geometry considerations remains less than that of horizontal positions. It is not uncommon for satellite heights to be off from map elevations by +/- 400 ft. Use these values with caution when navigating. |
|