AlpineQuest & OfflineMaps

There is a brief message about being unable to handle the ellipsoid for e.g., TWD67, and the program continues to function.

1. The user might not even notice, and think the ellipsoid has been applied, causing him to communicate incorrect coordinates to his co-workers.
2. Also this message is seen in exactly the same fashion even if the current grid is not the grid affected.

Hi and thanks for your feedback.

I'm sorry if you had issues using this system in the app. I have updated the warning message and added a dialog, forcing the user better acknowledge what's going on.
In some systems, the ellipsoid transformation is needed (the resulting error is smaller than the GPS accuracy), so that's why the app still accepts the format and process the map projection.

Now concerning TWD67, I've found conversion parameters and added them, but I haven't found any coordinates in this system so I'm unable to check them. If you want, you can test them by importing (or re-importing) the location format codes "EPSG:3827" or "EPSG:3828" (and restart the app).
Or if you have locations in both coordinates, I'd be glad to validate the parameters.

Best regards

Well in this case they would be off by a kilometer!
OK I'll try it, thanks.
See also
http://wiki.osgeo.org/wiki/Taiwan_datums/Test_points
http://wiki.osgeo.org/wiki/Category:Taiwan

Thanks for the data.
I think I have successfully validated the conversion parameters...
It wasn't easy tough: I wanted to check the points using QGIS, but it doesn't handle the ellipsoid conversion too, but horror, not a single message about this! That's even more bad than our simple warning message.
Then, using your first line point ("N355"), I couldn't found any match, until I realized your WGS84 location doesn't match the TWD97 coordinates... However, the conversion from TWD97 to TWD67 is OK, and I now find the same result in the app. Are you sure of your WGS84 coordinates?

Be sure to report the QGIS bug.

All I know is that there also is perl
Geography::NationalGrid::TW
and http://www.sunriver.com.tw/grid_tm2.htm
Any you can try
http://www.sunriver.com.tw/taiwanmap/gr ... onvert.php
or even http://www.sunriver.com.tw/taiwanmap/gr ... onvert.php which has my photo from 1999.
And in my mind TWD97 and WGS84 are only centemeters apart, whilst TWD67 is a whole kilometer away.

Thanks, so the new conversion is OK.
Be sure to re-import these coordinate systems to get the correct ones:
- "EPSG:3826" for TWD97 (zone 121);
- "EPSG:3828" for TWD67 (zone 121).

Will there be an updated Offline Maps in Google Play that I upload first?

No no you don't need a new app version, just to update the coordinate systems. The app will update them from our servers (with the corrected version).