n closest points in a set of lat/long coordinates

Here's my problem:

I have a website where people can search based on their location (which is converted to lat/long coordinates). I have many products stored in a database with their lat/long coordinates. I also have a function to calculate the distance between two points based on their coordinates.

Now I'm looking for a way to find one of these things:

• The n nearest products to the user's location.

• All the products within a radius of x kilometers from the user's location.

Both solutions would be fine for my application.

Currently I just iterate over all the database entries, find their distance, and sort them. This obviously gets way too slow with a lot of entries.

Are there any algorithms/data structures I can apply here to make it faster?

Thanks in advance!

Your problem (at least the second variant) is known as 2D range searching. Commonly used data structures are range trees and k-d trees. Searching for range searching on the web will open you a window into the area. These lecture notes come up, for example.

StackExchange Computer Science Q#41418, answer score: 2