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> I don't know of any freely available database where you can provide an arbitrary polygon of geographical coordinates and it will return the points within that

> I don't know of any freely available database where you can provide an arbitrary polygon of geographical coordinates and it will return the points within that polygon. MySQL geo extensions do this, explicitly. See: http://dev.mysql.com/doc/refman/4.1/en/relations-on-geometry-mbr.html http://dev.mysql.com/doc/refman/4.1/en/relations-on-geometry... I'll give you that you can only really do MBR queries, but it's easy enough to approximate this to arbitrary polygons (and functions to do so are google-able). I've always felt that all the worry about Geo being hard was mostly FUD. You can easily build a highly location aware application on a grid system without even using any true geospatial index and indeed one of the largest local sites does (see my profile)! Shapefiles aren't really all that horrible either since Tiger (i.e. US Census data) has gotten a lot better in the past couple years. You can relatively easily hack together a geocoding service in a fews days provided you have enough caffeine.

nosignal 15y ago
I guess, to nitpick, he means "any currently existing, freely accessible POI databases which support arbitrary polygon selection". Eg. most services which support "geospatial queries" (Flickr, Yelp, etc) only support MBR or simple geometry queries rather than true polygon intersects. Which I also misinterpreted but is also true (to my knowledge anyway). He's not saying it's impossible to set one up for yourself using PostGIS etc — if anything, that's his point. I agree with you that it's simple enough to set one up for yourself that the value offered by a service is minimal.
- newhouseb 15y ago
  Well he lists MongoDB and PostGIS as DBs that don't allow polygon selection, but your alternate interpretation is more truthful. Yelp does do arbitrary polygon intersections on the backend for neighborhood queries, but I guess this isn't exposed in any API.

nosignal 15y ago

I guess, to nitpick, he means "any currently existing, freely accessible POI databases which support arbitrary polygon selection". Eg. most services which support "geospatial queries" (Flickr, Yelp, etc) only support MBR or simple geometry queries rather than true polygon intersects. Which I also misinterpreted but is also true (to my knowledge anyway). He's not saying it's impossible to set one up for yourself using PostGIS etc — if anything, that's his point. I agree with you that it's simple enough to set one up for yourself that the value offered by a service is minimal.

newhouseb 15y ago
Well he lists MongoDB and PostGIS as DBs that don't allow polygon selection, but your alternate interpretation is more truthful. Yelp does do arbitrary polygon intersections on the backend for neighborhood queries, but I guess this isn't exposed in any API.