Optimum search with geospatial coordinates

Tod Hansmann plug.org at todandlorna.com
Tue Mar 18 20:51:45 MDT 2014


On 3/18/2014 8:32 PM, S. Dale Morrey wrote:
> I have a resource constrained system that contains a map and a list of
> points on the map given as longitude and latitude.
> Each point is it's own seperate object.
> I also have a point on the map that corresponds to the user's current
> location.
>
> What I want to do is search all of the points in the map and return the one
> closest to the user.
> The long and lat are both signed doubles (language is Java but the
> principles should basically be the same).
>
> What would be the optimal search given that the list of points is contained
> in a Vector (array).
> I'm thinking something like a loop that goes through each item and compares
> the long and lat differences for the smallest differences.  But that seems
> to me like a suboptimal solution.
> I have access to background threads and I do wonder about maybe 2 threads
> doing this, but one counting from the front of the array and another
> counting from the back.  At present there are only a couple of hundred
> points, but it's possible in the future that the list might balloon to
> thousands.
>
> Anyways just hoping someone knows of a better search method.
>
Fix your data formats?  At least if you're going to do this search a lot 
or need it to be quicker.

-Tod Hansmann


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