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On Apr 23, 2007, at 2:04 PM, Henning Schulzrinne wrote:
Holes in that boundary don't affect the centroid-based search. What
will happen depends a bit on the way the information is stored. In
simple cases, where the PSAPs serving the hole are stored in the
same authoritative server (or represented as summaries in those
servers), a point that hits that hole will generate two matches:
the surrounding-area PSAP and the more specific one. The server
can then inspect the holes registered for the surrounding-area PSAP
and discover easily that the special-case PSAP for the hole is the
right answer. There are optimizations you can do to make this
efficient, in particular since the area of the hole is by
definition smaller than the surrounding area (without taking the
whole into account).
So, how does a server know that the input polygon should match an
exact polygon in the db (as is needed for the VSP test) vs a need to
find the centroid before looking for a match (as would be needed for
regular uses of LoST)? In the first case, the VSP test will fail
because it will match the more specific polygon, according to your
description above.
-andy
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