I had an application which had 5 cm meter accuracy and needed to get points with 1 meter for example. I ended up writing my own search method. I'm sure others are trying to do similar. The patch I submitted doesn't change the original code at all unless you enable the RTREE_DOUBLE. So it should be perfectly safe to apply. Could probably be done better but it's isolated right now. Michael D. Black Senior Scientist Advanced Analytics Directorate Northrop Grumman Information Systems
________________________________ From: sqlite-users-boun...@sqlite.org on behalf of Richard Hipp Sent: Thu 11/4/2010 10:49 AM To: General Discussion of SQLite Database Subject: EXTERNAL:Re: [sqlite] R*Tree module and double precision? On Thu, Nov 4, 2010 at 11:27 AM, Ben Harper <b...@imqs.co.za> wrote: > Are you sure that double precision in the RTree is necessary for your > purposes? > To put this another way, single-precision RTree is sufficient to locate any point on the surface of the earth to within less than 2.5 meters. I'm curious to know what real-world application needs more precision than that? Remember that R-Tree is intended as a approximation filter to limit the search space for a query. It does not normally yield the definitive answer. Instead, R-Tree returns a superset of the answer which is further refined by lower-level constraints. Within 2.5 meters over the entire surface of the earth is not a close enough approximation? > > Here is a table of floating point precision at various values: > > The 'flip' values are the 'org' values with the lowest bit flipped. > > org flip ( delta) > 0.01 0.01 ( 0.000000) (lowest bit is 10 ^ -9.030900) > 0.10 0.10 ( 0.000000) (lowest bit is 10 ^ -8.127810) > 1.00 1.00 ( 0.000000) (lowest bit is 10 ^ -7.224720) > 10.00 10.00 ( 0.000001) (lowest bit is 10 ^ -6.020600) > 100.00 100.00 ( 0.000008) (lowest bit is 10 ^ -5.117510) > 1000.00 1000.00 ( 0.000061) (lowest bit is 10 ^ -4.214420) > 10000.00 10000.00 ( 0.000977) (lowest bit is 10 ^ -3.010300) > 99999.99 99999.98 ( 0.007813) (lowest bit is 10 ^ -2.107210) > 999999.94 999999.88 ( 0.062500) (lowest bit is 10 ^ -1.204120) > 9999999.00 9999998.00 ( 1.000000) (lowest bit is 10 ^ 0.000000) > 99999992.00 99999984.00 ( 8.000000) (lowest bit is 10 ^ 0.903090) > 999999936.00 999999872.00 (64.000000) (lowest bit is 10 ^ 1.806180) > > > -----Original Message----- > From: sqlite-users-boun...@sqlite.org [mailto: > sqlite-users-boun...@sqlite.org] On Behalf Of Black, Michael (IS) > Sent: 04 November 2010 02:51 PM > To: General Discussion of SQLite Database > Subject: Re: [sqlite] R*Tree module and double precision? > > I'll send the patched C file to your email address. I think the 1M patched > version is a bit much for the email list. > > Normally you would just use the "patch" utility to apply the patch to your > file. > > Michael D. Black > Senior Scientist > Advanced Analytics Directorate > Northrop Grumman Information Systems > > > ________________________________ > > From: sqlite-users-boun...@sqlite.org on behalf of > jsarc...@nanotronicsimaging.com > Sent: Wed 11/3/2010 10:22 AM > To: sqlite-users@sqlite.org > Subject: EXTERNAL:Re: [sqlite] R*Tree module and double precision? > > > > >From: "Black, Michael (IS)" <michael.bla...@ngc.com> I made a patch > >which seems to do this for you... > >Use this switch to enable double precision on RTREE /DRTREE_DOUBLE > > I am interested in this as well. Will this patch be included in a future > version of SQLite? Or, if not, how best to make use of this patch if I > normally use the amalgamation from C++. > Jeff Archer > Nanotronics Imaging > jsarc...@nanotronicsimaging.com > <330>819.4615 > _______________________________________________ > sqlite-users mailing list > sqlite-users@sqlite.org > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > > > _______________________________________________ > sqlite-users mailing list > sqlite-users@sqlite.org > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > -- D. Richard Hipp d...@sqlite.org _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
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