Obfuscate location data

[YaguraStation]

At Codebridge Newlands (Thu Jan 24 '19) we heard of the challenge to obfuscate location data, but still having it fairly accurate to make reasonable assessments and decisions.

Speaking to @ricki-z from @opendata-stuttgart who also obfuscate sensor location data on https://maps.luftdaten.info/ to protect the privacy of project participants, they round off the coordinates to 1/500 of a degree (distance approx. 100m).

In some cases, by chance, this might just as well be the exact location ;-). If security is still an issue with rounding, they suggest to maybe do the following: random value (0-50m) + constant (e.g. 50m), with direction random.

[Marwe]

https://github.com/Marwe/particlemap/blob/master/static/grid001.json visualises cutoff at third digit. This is the grid used for luftdaten. Should be around 100m (east-west distance changes with longitude - largest at equator, 0 at poles).

[ricki-z]

This is the same as the first option (rounding to 1/1000 degree). And as mentioned a station may have a position exactly on this raster. So in this case this may not be an option.