Re: earthdistance

On Sat, Aug 10, 2013 at 12:18:48 +0200,
Olivier Chaussavoine <olivier(dot)chaussavoine(at)gmail(dot)com> wrote:
>I did not found any geographic indexing with earthdistance, and need it.

Some of the earthdistance stuff is based on cube which does have indexing.
I don't know how well that indexing works and it might be pretty bad in
practice.

>The need I have is simple:
>"is the distance between two (lat,long) positions less than X km?"
>the model used for the shape of the earth should be related to the
>precision of lat,lon, and most sources are imprecise. The spherical model
>should be enough.

You might just be looking at this wrong. You don't have an index on the
distance. What you want is to find points within a cube that is big enough
to include all of the points of interest and then double check the returned
points to make sure they are really within the expected range. You can
calculate the size of the cube needed based on the distance and the
radius of the earth. I don't remember if there was a built in function
for that, since it's been such a long time since I looked at it.