从地址查找给定英里半径内的城市

Question

I'm using CakePHP/mysql to build my app and I'm trying to get a list of cities within a given mile radius around an address both supplied by the user. So far I have a list of all US cities in a database with the long/lat. I also am using a CakePHP plugin to get the long/lat of all addresses inserted into the database.

Now how do I do the last part? I'm new to the google maps api but it looks like there is a limit on how many queries I make a day. The only way I can think to do it is to check the distance from the address and compare it to every city in the database and if it is within the given radius then they are selected. It seems like this would be way too database intensive and I would pass my query quotas in one go.

Any ideas?

Answer 1

It sounds like you're trying to determine if a given point (city) is within a circle centered on a specific lat/lon. Here's a similar question .

Run a loop over each city and see if it satisfies the following condition:

if ( (x-center_x) ² + (y-center_y) ² <= radius ² )

If this is too slow, you could turn it into a lookup based on rounding the lat/lon. The more values you precompute, the closer to exact you can get.