Exporting High Accuracy GPS
Note: this feature is only available when processing data from a DL2 and is only required for specialist applications, for most applications it is advised to use the normal export system which is explained here.
Internally the analysis software uses standard IEEE single precision arithmetic, this is the equivalent of about 8 digits of precision. Whilst gives enough accuracy for all “standard” variables such as speed, acceleration, temperature, relative postion etc, it is not enough to give enough resolution on GPS time of week, GPS latitude and GPS longitude. In practice it means that if GPS latitude and GPS longitude are exported using the normal export tools you only get about 1-2m of precision which is not enough for some applications.
To get around this problem, every time a run is processed, the software generates a file called "GpsData.csv" that contains high precision:
- Data logger sample time
- GPS week
- GPS TOW
- Velocity Accuracy
- Positional Accuracy
A few additional notes:
- It is generated when you process a run, the old file is deleted and a new one generated.
- It only works for the DL2, it is disabled for the DL1 at this time.
- It works in all “raw” GPS modes, at the time of writing this includes standard 5Hz, post processed 20Hz, and PPP post processed 20Hz.
- There are no options or flags to control the output of this file.
- The Data logger sample numbers can be used to match the data back into a full export of the data if required.