Re: SDO_NN with Oracle Spatial 10g

When SDO_SRID is null, the system does no interpretation or conversion of the coordinates. For things like sdo_nn, it appears that 'x', 'y' and 'z' axis are assumed othorgonal and assumed to use the same units.

In general I find that sdo_nn attempts to do surface-based nn calculations, so ideally on your unit circle we would be using a pure greater circle arc - but accomplished through projections. However, since you have srid set null, the system has no way of projecting that to a flat surface, and indeed assumes flat surface topology. On initial review, I suspect this is at least part of the issue you are seeing.

I wonder whether Oracle put in a 'unit circle' coordinate system. They have an SRID for Mars (2000001), so why not? Something to check ...

Do you have a support contract? This would be a perfect question to raaise as a support TAR.

-- 
Hans Forbrich                           
Canada-wide Oracle training and consulting
mailto: Fuzzy.GreyBeard_at_gmail.com   
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