Sort relative distance on the fly

rubyonrails-talk
1

Hi I am quite a newbie in Ruby. I want to sort a list of locations by relative distance (shortest to farthest relative to my location) on the fly. For example, let say I am at x and y coordinate, I have other points in the map around me. I want to be able to list the other points in terms of the shortest distance from me to the farthest. I store longitude and latitude information on the database. However, I cannot store the relative distance permanently, as (i) number of points change in real time; and (ii) I don't have relationship with the other points, which means the many-to-many tables are still empty.

Any ideas?

2

Google for "earth distance sql"... or trust that the below is right :slight_smile:

This assumes that some_table has columns for latitude and longitude and that you've set variables for latitude, longitude and radius (in miles) to search on.

SELECT * FROM some_table WHERE (3960 * 2 * ASIN( SQRT( (1 - COS(RADIANS(latitude - #{latitude}))) / 2 + COS(RADIANS(#{latitude})) * COS(RADIANS(latitude)) * (1 - COS(RADIANS(longitude - #{longitude}))) / 2))) <= #{radius}

3

Philip Hallstrom wrote: