[DerWOK]

For Geo-Location, maybe consider this workflow: User searches City in the iPhone Maps App (by Apple), then clicks "Share" button, then "Copy to Clipboard" - thenpaste this location into your app, you grab Longitude & Latitude from that and let users specify a radius. Bam! Complicated.... But no network needed.

[netsharc]

Someone else has commented with a list of cities which could be included offline: https://news.ycombinator.com/item?id=34690693

But your workflow is such a hassle that I doubt many people would do it. A more realistic flow (without the list of places above) would be to show an image of the world map, allow the user to zoom in, and let them drop a pin on the map. They can drop a pin near some pixels labeled Paris, but the app doesn't need to know that it's Paris, it just needs to translate the pixel coordinates of the pin (relative to the image) to geographical coordinates, and look for images close to these coordinates.

[4lun]

Potentially the app could link out to a hosted webpage that allows selecting a location using a decent map and search UI, with network capability (but without requiring it in app)

Then on selecting a location you present a button that then jumps you back into the app via a universal link (passing in lon/lat)