GrazianoCapelli
commented
5 years ago Yes, the feature you reported is present in GPS Logger starting from v2.1.7.
You can load the EGM grid by copying the WW15MGH.DAC EGM file in the /GPSLogger/AppData/ folder of your internal device memory.
Please note that, on android 6+, the Storage Permission must be granted to GPS Logger in order to load it.
This feature may be useful in the following cases:
- You already downloaded the EGM file and you simply want to use it with the app
- You installed GPS Logger on a phone that, for any reason, cannot reach the NGA website
- You want to use the automatic correction with a different data set
When you activate the EGM grid, the app reasons as follows:
1) The app looks into its private FilesDir folder.
If the WW15MGH.DAC EGM file is found, the app loads it (after a size check)
2) If the file is not present in its private folder, the app looks into the shared /GPSLogger/AppData/ folder (if the folder is present, and compatibly with the permission to access to the storage).
If the WW15MGH.DAC EGM file is found, the app loads it and copy it into its private FilesDir folder.
In this case, the next time the EGM grid is loaded, the app will delete the EGM file from the shared folder, because it can find that on its private folder.
3) If the app cannot find the EGM file in both locations, the file is downloaded from the NGA website.
@DazzyWalkman Thank you for talking about this hidden feature!
We'll take this opportunity to document it on the GPSLogger's section of the BasicAirData website. I leave the issue open, we'll close it as soon as the feature will be documented.
DazzyWalkman
This issue does NOT require any action from the developer. I open this issue only to share my little "findings".
The app will download EGM grid from: http://earth-info.nga.mil/GandG/wgs84/gravitymod/egm96/binary/WW15MGH.DAC. This is essentially a US military website, that means it's inaccessible from certain parts of the world, thus users of this app in these regions will not be able to download EGM grid from the above website.
I am one of them. I just query the WW15MGH.DAC via search engine, and find suitable mirror links to download the file, then place it into the phone internel storage /GPSLogger/AppData/ folder or whatever user-config FileDir.
It seems to work well, though I cannot share links for I can't back the authenticity of such file from unknown sources.
Hope it helps.