On Wed, 2009-07-01 19:13:26 +0100, Jon Burgess <[email protected]> wrote: > On Wed, 2009-07-01 at 13:51 +0200, Etienne Chové wrote: > > Etienne Chové a écrit : > > > The difference is not really significant but postgis says > > > polygons are olvelapping each other while they have just a > > > common boundary. > > > > The errors doesn't appear when I delete lines "#define > > FIXED_POINT" in middle_ram.c and middle_pgsql.c > > > > Is it danerous to delete them ? > > I have come across this issue before, the 'slim' mode can fetch the node > positions from the DB or from a RAM cache. The DB stores the positions > in doubles (giving 53 bits of precision), the RAM cache uses fixed point > arithmetic giving around 32 bits of precision. 32 bits is perfectly > sufficient for OSM and halves the storage size.
Are you 100% sure about that comment?
ISTR that at some time, I calculated the accuracy of 32bit (float) at
the aequator, which resulted in +/- 15cm or the like. This may or may
not be enough...
MfG, JBG
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