[hibernate-dev] Coordinates storage in Lucene index for spatial functionality

[Nicolas Helleringer]

Hi all,

Sanne and I have been wondering about the way the spatial
branch/module/functionality for Hibernate Search shall store its
coordinates in the Lucene index.

Today it is implemented with decimal degree for :
- easy debugging/readability
- ease of conversion on storage as we want to accept mainly decimal degree
from users data

Sanne pointed out that when the search is done there is quite a few
conversion to radians for distance calculation and suggested that we may
store directly coordinates under their radians form.

I have tried a patch to implement this and as I was coding it I feel that
the code was less readable, in the coordinates normalisation mainly and
that there was as many conversion as before.
Conversions had moved from search to import / export of coordinates in and
out the spatial module scope to user scope.

What the docs does not tell (yet), is that we are waiting for WGS 84 (this
is a coordinate system) decimal degree coordinates input, as these are
quite a de facto standard (GPS output this way).

Today this is not the purpose of Hibernate Search spatial initiative to
handle projections. There are opensource libs to handle that on user side
very well (Proj4j)

So. The question is : shall we store as radians or decimal degree ?

Niko

P.S : Hope it is clear. If not ask for more.