@ggalmazor. Thanks for your work so far.
Unfortunately I got the problem, that when I export my test-data with Briefcase as GeoJSON, the geometry-field is null. CSV works fine though.
I think you can check it by yourself, here is my data:
It would be great to use it in my fieldwork! I simply love to use open source.. 
Hi, @bastoGrande!
The sandbox server resets every Saturday and I was on leave for the last two weeks. Could you push the form again, please? This week I can check this and try to debug it.
Right now I'm not home and can't test if it's reproducible (don't know how to use briefcase on my manjaro-linux), but on uploaded again a form (BriefcaseDemo) to the sandbox server. Hope this helps..
Hi, @bastoGrande!
I've just tried to pull & export with Briefcase v1.14 your form from the sandbox server and I got a valid GeoJSON. Can you tell us what you've tried so far, and how it fails?
This is the GeoJSON I got:
{"type":"FeatureCollection","features":[{"type":"Feature","properties":{"valid":"yes","field":"Gewaesser","key":"uuid:ad8cfaf7-68c8-4a2a-8b6f-37f5042eabe7","empty":"no"},"geometry":{"type":"Polygon","coordinates":[[[10.639759410511349,53.33146942963275,0.0],[10.247247869318175,53.061024759862775,0.0],[10.1953125,53.34697411465316,0.0],[10.477960759943175,53.415484940742154,0.0],[10.639759410511349,53.33146942963275,0.0]]]}}]}
You can verify at geojson.io that it's a valid GeoJSON document.
sorry for the extremly late reply!
Well I don't know why it didn't work the first time, but now it seems alright.. might be a strange set of circumstances... 
anyway, thanks for your effort!
