Replace usage of Nominatim with pg-nearest-city

[spwoodcock]

Is your feature request related to a problem? Please describe.

• Nominatim is a great web reverse geocoder, hosted for free by OSM.
• We don't need detailed reverse geocoding to an address. Instead projects can be reverse geocoded to the nearest city of 1000 people.

Describe the solution you'd like

• We made a package for FieldTM to do exactly that: github.com/hotosm/pg-nearest-city/
• Using the underlying PostGIS database, we can reverse geocode during project creation, entirely offline.
• Usage of Nominatim can be removed, also reducing the load on the OSM-hosted server during testing / project creation.

[allisonsibrian]

I've been trying to find the codebase for Nominatim, but can't find it. Where can I find the file with the Nominatim implementation? Thanks!

[spwoodcock]

Hey @allisonsibrian, so it looks like it's here in the backend code:

drone-tm/src/backend/app/utils.py

Lines 236 to 242 in c2b13fb

	def get_address_from_lat_lon(latitude, longitude):
	"""Get address using Nominatim, using lat,lon."""
	base_url = "https://nominatim.openstreetmap.org/reverse"
	params = {
	"format": "json",
	"lat": latitude,

But that said, unfortunately it seems the dev team decided to migrate this logic to the frontend: https://github.com/hotosm/drone-tm/blob/c2b13fb4c6475631bf295949443aa2aa9862df76/src/frontend/src/services/common.ts
(the backend code is no longer used...)

On top of that, the code at pg-nearest-city is still awaiting a bit of finalisation after we discovered a bug: hotosm/pg-nearest-city#34

So this issue is blocked until:

• The PR linked above is merged
• The frontend nominatim code is refactored out, in favour of using pg-nearest-city via an API call during project creation

Sorry about this! I might be best you look into a different issue 😅