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Sphere or Spheroid
by Paul Ramsey-4
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I am just now hooking up some spheroid calculations into SQL and the
choice is here: what is the default return for ST_Distance(geog, geog) ? I have an extra signature ST_Distance(geog, geog, bool) which allows you to choose, *but* something has to be the default. So, slow and accurate or fast and not-quite-right? For reference, here's some test numbers: spheroid | sphere | diff | diff_pct ------------------+------------------+----------------------+----------------------- 14.1244075108035 | 14.1394160043876 | -0.0150084935841761 | -0.00106146488507862 14.6266188748041 | 14.5910056309084 | 0.0356132438956287 | 0.00244076692151968 20.7346086743544 | 20.7259709082645 | 0.00863776608995082 | 0.000416760504402065 21.9682444424626 | 21.9811452394388 | -0.0129007969762469 | -0.000586902858596291 23.7383733187578 | 23.7519404190066 | -0.0135671002487641 | -0.000571199658193295 24.71417232105 | 24.6751858115921 | 0.0389865094578177 | 0.00157998848541607 26.060846145618 | 25.9957171978245 | 0.0651289477934469 | 0.00250537222334829 29.1593418185795 | 29.0828389449609 | 0.0765028736186224 | 0.00263051601542076 30.4726043383638 | 30.407477679772 | 0.0651266585918009 | 0.00214179746434954 33.3089494734479 | 33.2231927324098 | 0.085756741038054 | 0.00258123118174602 54.5278744382593 | 54.5740236709768 | -0.0461492327175321 | -0.000845626355054244 56.6270596077484 | 56.4794616931023 | 0.147597914646141 | 0.00261330243280571 58.0564235524421 | 57.9072919817022 | 0.149131570739875 | 0.00257535045477517 61.5962238336604 | 61.6609971505153 | -0.0647733168549323 | -0.00105047468980788 61.7015675105702 | 61.5433341315128 | 0.158233379057449 | 0.00257108883180295 67.6094786823676 | 67.4707740811243 | 0.138704601243305 | 0.00205577308297266 68.2569872101138 | 68.0830690889332 | 0.173918121180577 | 0.00255449884248604 68.4943435865133 | 68.5554249222873 | -0.0610813357739914 | -0.000890977422184046 68.5746705524887 | 68.4885568487924 | 0.0861137036962845 | 0.00125734440406453 68.6758026445452 | 68.7123761613873 | -0.0365735168421395 | -0.000532269714501474 73.4229241308488 | 73.4212994751178 | 0.00162465573099269 | 2.21278531244639e-05 79.4484754792361 | 79.4536134385929 | -0.00513795935687256 | -6.46661509088383e-05 85.4392924899187 | 85.3402382287158 | 0.0990542612029799 | 0.00116069820355446 85.4539811995932 | 85.3919394786419 | 0.0620417209512425 | 0.00072655242789936 93.5788665631846 | 93.4985937971677 | 0.0802727660169325 | 0.000858545169043645 96.3199573238008 | 96.1797387047942 | 0.14021861900666 | 0.00145788105577033 101.328501281213 | 101.062654489096 | 0.265846792116648 | 0.00263051463926598 101.649559586565 | 101.502533562595 | 0.14702602397027 | 0.00144849609965254 108.809850830453 | 108.894277925073 | -0.0844270946195422 | -0.000775312497848917 109.397307465226 | 109.316521134613 | 0.0807863306121561 | 0.000739013003466101 110.654864554623 | 110.763015546595 | -0.108150991971058 | -0.000976417908426867 113.60376179349 | 113.561772904965 | 0.0419888885251396 | 0.000369744919007898 114.121155128581 | 113.828085749691 | 0.293069378889427 | 0.00257466667351227 114.310532244975 | 114.431988777869 | -0.121456532893603 | -0.00106138619271374 115.797340494535 | 115.877511025684 | -0.0801705311490082 | -0.000691855826375479 116.509315790761 | 116.204507950436 | 0.304807840325097 | 0.00262302939620126 116.944936442573 | 116.776885086999 | 0.168051355574235 | 0.00143908064895751 118.802848975488 | 118.599760910854 | 0.203088064634358 | 0.00171238173732078 124.752683002401 | 124.793829377275 | -0.0411463748743159 | -0.000329714819071083 _______________________________________________ postgis-devel mailing list postgis-devel@... http://postgis.refractions.net/mailman/listinfo/postgis-devel |
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Re: Sphere or Spheroid
by Paul Ramsey-4
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I should add that in general, the differences seem to be about 0.1% to
0.2% for my Oregon test area. P. On Fri, Oct 30, 2009 at 1:39 PM, Paul Ramsey <pramsey@...> wrote: > I am just now hooking up some spheroid calculations into SQL and the > choice is here: what is the default return for ST_Distance(geog, geog) > ? I have an extra signature ST_Distance(geog, geog, bool) which allows > you to choose, *but* something has to be the default. So, slow and > accurate or fast and not-quite-right? For reference, here's some test > numbers: > > spheroid | sphere | diff | > diff_pct > ------------------+------------------+----------------------+----------------------- > 14.1244075108035 | 14.1394160043876 | -0.0150084935841761 | > -0.00106146488507862 > 14.6266188748041 | 14.5910056309084 | 0.0356132438956287 | > 0.00244076692151968 > 20.7346086743544 | 20.7259709082645 | 0.00863776608995082 | > 0.000416760504402065 > 21.9682444424626 | 21.9811452394388 | -0.0129007969762469 | > -0.000586902858596291 > 23.7383733187578 | 23.7519404190066 | -0.0135671002487641 | > -0.000571199658193295 > 24.71417232105 | 24.6751858115921 | 0.0389865094578177 | > 0.00157998848541607 > 26.060846145618 | 25.9957171978245 | 0.0651289477934469 | > 0.00250537222334829 > 29.1593418185795 | 29.0828389449609 | 0.0765028736186224 | > 0.00263051601542076 > 30.4726043383638 | 30.407477679772 | 0.0651266585918009 | > 0.00214179746434954 > 33.3089494734479 | 33.2231927324098 | 0.085756741038054 | > 0.00258123118174602 > 54.5278744382593 | 54.5740236709768 | -0.0461492327175321 | > -0.000845626355054244 > 56.6270596077484 | 56.4794616931023 | 0.147597914646141 | > 0.00261330243280571 > 58.0564235524421 | 57.9072919817022 | 0.149131570739875 | > 0.00257535045477517 > 61.5962238336604 | 61.6609971505153 | -0.0647733168549323 | > -0.00105047468980788 > 61.7015675105702 | 61.5433341315128 | 0.158233379057449 | > 0.00257108883180295 > 67.6094786823676 | 67.4707740811243 | 0.138704601243305 | > 0.00205577308297266 > 68.2569872101138 | 68.0830690889332 | 0.173918121180577 | > 0.00255449884248604 > 68.4943435865133 | 68.5554249222873 | -0.0610813357739914 | > -0.000890977422184046 > 68.5746705524887 | 68.4885568487924 | 0.0861137036962845 | > 0.00125734440406453 > 68.6758026445452 | 68.7123761613873 | -0.0365735168421395 | > -0.000532269714501474 > 73.4229241308488 | 73.4212994751178 | 0.00162465573099269 | > 2.21278531244639e-05 > 79.4484754792361 | 79.4536134385929 | -0.00513795935687256 | > -6.46661509088383e-05 > 85.4392924899187 | 85.3402382287158 | 0.0990542612029799 | > 0.00116069820355446 > 85.4539811995932 | 85.3919394786419 | 0.0620417209512425 | > 0.00072655242789936 > 93.5788665631846 | 93.4985937971677 | 0.0802727660169325 | > 0.000858545169043645 > 96.3199573238008 | 96.1797387047942 | 0.14021861900666 | > 0.00145788105577033 > 101.328501281213 | 101.062654489096 | 0.265846792116648 | > 0.00263051463926598 > 101.649559586565 | 101.502533562595 | 0.14702602397027 | > 0.00144849609965254 > 108.809850830453 | 108.894277925073 | -0.0844270946195422 | > -0.000775312497848917 > 109.397307465226 | 109.316521134613 | 0.0807863306121561 | > 0.000739013003466101 > 110.654864554623 | 110.763015546595 | -0.108150991971058 | > -0.000976417908426867 > 113.60376179349 | 113.561772904965 | 0.0419888885251396 | > 0.000369744919007898 > 114.121155128581 | 113.828085749691 | 0.293069378889427 | > 0.00257466667351227 > 114.310532244975 | 114.431988777869 | -0.121456532893603 | > -0.00106138619271374 > 115.797340494535 | 115.877511025684 | -0.0801705311490082 | > -0.000691855826375479 > 116.509315790761 | 116.204507950436 | 0.304807840325097 | > 0.00262302939620126 > 116.944936442573 | 116.776885086999 | 0.168051355574235 | > 0.00143908064895751 > 118.802848975488 | 118.599760910854 | 0.203088064634358 | > 0.00171238173732078 > 124.752683002401 | 124.793829377275 | -0.0411463748743159 | > -0.000329714819071083 > postgis-devel mailing list postgis-devel@... http://postgis.refractions.net/mailman/listinfo/postgis-devel |
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Re: Sphere or Spheroid
by Paragon Corporation-2
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Paul,
My vote would be fast and not quite right. Though would be helpful if you could better quantify your "slow" vs. "fast" definition since I think that would be more of a deciding decision. I assume it would depend on the number of points, size of geometry and holes in a geometry but pick a reference geometry size and tell us the differences in speed. Probably 2 or 3 sets of the same geometry positioned across the globe (worst case geom, average geom, point) (and for each give some relative timings). I'm still dreaming of the GUC by the way. http://trac.osgeo.org/postgis/ticket/267 to make this decision less relevant. What is bool (will that mean True if you want measured in sphere?). Regardless of what default you decide, that boolean has to mean the same thing I think. (but I guess that's not too important) Thanks, Regina -----Original Message----- From: postgis-devel-bounces@... [mailto:postgis-devel-bounces@...] On Behalf Of Paul Ramsey Sent: Friday, October 30, 2009 4:41 PM To: PostGIS Development Discussion Subject: Re: [postgis-devel] Sphere or Spheroid I should add that in general, the differences seem to be about 0.1% to 0.2% for my Oregon test area. P. On Fri, Oct 30, 2009 at 1:39 PM, Paul Ramsey <pramsey@...> wrote: > I am just now hooking up some spheroid calculations into SQL and the > choice is here: what is the default return for ST_Distance(geog, geog) > ? I have an extra signature ST_Distance(geog, geog, bool) which allows > you to choose, *but* something has to be the default. So, slow and > accurate or fast and not-quite-right? For reference, here's some test > numbers: > > spheroid | sphere | diff | diff_pct > ------------------+------------------+----------------------+--------- > ------------------+------------------+----------------------+--------- > ------------------+------------------+----------------------+----- > 14.1244075108035 | 14.1394160043876 | -0.0150084935841761 | > -0.00106146488507862 > 14.6266188748041 | 14.5910056309084 | 0.0356132438956287 | > 0.00244076692151968 > 20.7346086743544 | 20.7259709082645 | 0.00863776608995082 | > 0.000416760504402065 > 21.9682444424626 | 21.9811452394388 | -0.0129007969762469 | > -0.000586902858596291 > 23.7383733187578 | 23.7519404190066 | -0.0135671002487641 | > -0.000571199658193295 > 24.71417232105 | 24.6751858115921 | 0.0389865094578177 | > 0.00157998848541607 > 26.060846145618 | 25.9957171978245 | 0.0651289477934469 | > 0.00250537222334829 > 29.1593418185795 | 29.0828389449609 | 0.0765028736186224 | > 0.00263051601542076 > 30.4726043383638 | 30.407477679772 | 0.0651266585918009 | > 0.00214179746434954 > 33.3089494734479 | 33.2231927324098 | 0.085756741038054 | > 0.00258123118174602 > 54.5278744382593 | 54.5740236709768 | -0.0461492327175321 | > -0.000845626355054244 > 56.6270596077484 | 56.4794616931023 | 0.147597914646141 | > 0.00261330243280571 > 58.0564235524421 | 57.9072919817022 | 0.149131570739875 | > 0.00257535045477517 > 61.5962238336604 | 61.6609971505153 | -0.0647733168549323 | > -0.00105047468980788 > 61.7015675105702 | 61.5433341315128 | 0.158233379057449 | > 0.00257108883180295 > 67.6094786823676 | 67.4707740811243 | 0.138704601243305 | > 0.00205577308297266 > 68.2569872101138 | 68.0830690889332 | 0.173918121180577 | > 0.00255449884248604 > 68.4943435865133 | 68.5554249222873 | -0.0610813357739914 | > -0.000890977422184046 > 68.5746705524887 | 68.4885568487924 | 0.0861137036962845 | > 0.00125734440406453 > 68.6758026445452 | 68.7123761613873 | -0.0365735168421395 | > -0.000532269714501474 > 73.4229241308488 | 73.4212994751178 | 0.00162465573099269 | > 2.21278531244639e-05 > 79.4484754792361 | 79.4536134385929 | -0.00513795935687256 | > -6.46661509088383e-05 > 85.4392924899187 | 85.3402382287158 | 0.0990542612029799 | > 0.00116069820355446 > 85.4539811995932 | 85.3919394786419 | 0.0620417209512425 | > 0.00072655242789936 > 93.5788665631846 | 93.4985937971677 | 0.0802727660169325 | > 0.000858545169043645 > 96.3199573238008 | 96.1797387047942 | 0.14021861900666 | > 0.00145788105577033 > 101.328501281213 | 101.062654489096 | 0.265846792116648 | > 0.00263051463926598 > 101.649559586565 | 101.502533562595 | 0.14702602397027 | > 0.00144849609965254 > 108.809850830453 | 108.894277925073 | -0.0844270946195422 | > -0.000775312497848917 > 109.397307465226 | 109.316521134613 | 0.0807863306121561 | > 0.000739013003466101 > 110.654864554623 | 110.763015546595 | -0.108150991971058 | > -0.000976417908426867 > 113.60376179349 | 113.561772904965 | 0.0419888885251396 | > 0.000369744919007898 > 114.121155128581 | 113.828085749691 | 0.293069378889427 | > 0.00257466667351227 > 114.310532244975 | 114.431988777869 | -0.121456532893603 | > -0.00106138619271374 > 115.797340494535 | 115.877511025684 | -0.0801705311490082 | > -0.000691855826375479 > 116.509315790761 | 116.204507950436 | 0.304807840325097 | > 0.00262302939620126 > 116.944936442573 | 116.776885086999 | 0.168051355574235 | > 0.00143908064895751 > 118.802848975488 | 118.599760910854 | 0.203088064634358 | > 0.00171238173732078 > 124.752683002401 | 124.793829377275 | -0.0411463748743159 | > -0.000329714819071083 > postgis-devel mailing list postgis-devel@... http://postgis.refractions.net/mailman/listinfo/postgis-devel _______________________________________________ postgis-devel mailing list postgis-devel@... http://postgis.refractions.net/mailman/listinfo/postgis-devel |
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Re: Sphere or Spheroid
by Paul Ramsey-3
::
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I did GUC research this morning and even did a GUC implementation! I
don't think it makes this decision any less relevant, because frankly the default will rule 95% of the users. So choosing the "right" default is a good idea. Anyhow, on the GUC, a module-controlled GUC has an issue, in that the GUC can't exist until it's initialized by the module, and the initialization routine for the module is not executed until the first time a module function is called. So, running "SET geography.use_spheroid = true" will return an error if it's the first thing you do, but will work if you first do something like "SELECT ST_AsText('POINT(0 0)'::geography)" to force the module to load In all, a non-happy situation, so I have opted for function signatures for now, unless someone can tell me I should do otherwise. P. On Fri, Oct 30, 2009 at 4:10 PM, Paragon Corporation <lr@...> wrote: > I'm still dreaming of the GUC by the way. > http://trac.osgeo.org/postgis/ticket/267 to make this decision less > relevant. > > What is bool (will that mean True if you want measured in sphere?). > Regardless of what default you decide, that boolean has to mean the same > thing I think. (but I guess that's not too important) > > Thanks, > Regina > > -----Original Message----- > From: postgis-devel-bounces@... > [mailto:postgis-devel-bounces@...] On Behalf Of Paul > Ramsey > Sent: Friday, October 30, 2009 4:41 PM > To: PostGIS Development Discussion > Subject: Re: [postgis-devel] Sphere or Spheroid > > I should add that in general, the differences seem to be about 0.1% to 0.2% > for my Oregon test area. > > P. > > On Fri, Oct 30, 2009 at 1:39 PM, Paul Ramsey <pramsey@...> wrote: >> I am just now hooking up some spheroid calculations into SQL and the >> choice is here: what is the default return for ST_Distance(geog, geog) >> ? I have an extra signature ST_Distance(geog, geog, bool) which allows >> you to choose, *but* something has to be the default. So, slow and >> accurate or fast and not-quite-right? For reference, here's some test >> numbers: >> >> spheroid | sphere | diff | diff_pct >> ------------------+------------------+----------------------+--------- >> ------------------+------------------+----------------------+--------- >> ------------------+------------------+----------------------+----- >> 14.1244075108035 | 14.1394160043876 | -0.0150084935841761 | >> -0.00106146488507862 >> 14.6266188748041 | 14.5910056309084 | 0.0356132438956287 | >> 0.00244076692151968 >> 20.7346086743544 | 20.7259709082645 | 0.00863776608995082 | >> 0.000416760504402065 >> 21.9682444424626 | 21.9811452394388 | -0.0129007969762469 | >> -0.000586902858596291 >> 23.7383733187578 | 23.7519404190066 | -0.0135671002487641 | >> -0.000571199658193295 >> 24.71417232105 | 24.6751858115921 | 0.0389865094578177 | >> 0.00157998848541607 >> 26.060846145618 | 25.9957171978245 | 0.0651289477934469 | >> 0.00250537222334829 >> 29.1593418185795 | 29.0828389449609 | 0.0765028736186224 | >> 0.00263051601542076 >> 30.4726043383638 | 30.407477679772 | 0.0651266585918009 | >> 0.00214179746434954 >> 33.3089494734479 | 33.2231927324098 | 0.085756741038054 | >> 0.00258123118174602 >> 54.5278744382593 | 54.5740236709768 | -0.0461492327175321 | >> -0.000845626355054244 >> 56.6270596077484 | 56.4794616931023 | 0.147597914646141 | >> 0.00261330243280571 >> 58.0564235524421 | 57.9072919817022 | 0.149131570739875 | >> 0.00257535045477517 >> 61.5962238336604 | 61.6609971505153 | -0.0647733168549323 | >> -0.00105047468980788 >> 61.7015675105702 | 61.5433341315128 | 0.158233379057449 | >> 0.00257108883180295 >> 67.6094786823676 | 67.4707740811243 | 0.138704601243305 | >> 0.00205577308297266 >> 68.2569872101138 | 68.0830690889332 | 0.173918121180577 | >> 0.00255449884248604 >> 68.4943435865133 | 68.5554249222873 | -0.0610813357739914 | >> -0.000890977422184046 >> 68.5746705524887 | 68.4885568487924 | 0.0861137036962845 | >> 0.00125734440406453 >> 68.6758026445452 | 68.7123761613873 | -0.0365735168421395 | >> -0.000532269714501474 >> 73.4229241308488 | 73.4212994751178 | 0.00162465573099269 | >> 2.21278531244639e-05 >> 79.4484754792361 | 79.4536134385929 | -0.00513795935687256 | >> -6.46661509088383e-05 >> 85.4392924899187 | 85.3402382287158 | 0.0990542612029799 | >> 0.00116069820355446 >> 85.4539811995932 | 85.3919394786419 | 0.0620417209512425 | >> 0.00072655242789936 >> 93.5788665631846 | 93.4985937971677 | 0.0802727660169325 | >> 0.000858545169043645 >> 96.3199573238008 | 96.1797387047942 | 0.14021861900666 | >> 0.00145788105577033 >> 101.328501281213 | 101.062654489096 | 0.265846792116648 | >> 0.00263051463926598 >> 101.649559586565 | 101.502533562595 | 0.14702602397027 | >> 0.00144849609965254 >> 108.809850830453 | 108.894277925073 | -0.0844270946195422 | >> -0.000775312497848917 >> 109.397307465226 | 109.316521134613 | 0.0807863306121561 | >> 0.000739013003466101 >> 110.654864554623 | 110.763015546595 | -0.108150991971058 | >> -0.000976417908426867 >> 113.60376179349 | 113.561772904965 | 0.0419888885251396 | >> 0.000369744919007898 >> 114.121155128581 | 113.828085749691 | 0.293069378889427 | >> 0.00257466667351227 >> 114.310532244975 | 114.431988777869 | -0.121456532893603 | >> -0.00106138619271374 >> 115.797340494535 | 115.877511025684 | -0.0801705311490082 | >> -0.000691855826375479 >> 116.509315790761 | 116.204507950436 | 0.304807840325097 | >> 0.00262302939620126 >> 116.944936442573 | 116.776885086999 | 0.168051355574235 | >> 0.00143908064895751 >> 118.802848975488 | 118.599760910854 | 0.203088064634358 | >> 0.00171238173732078 >> 124.752683002401 | 124.793829377275 | -0.0411463748743159 | >> -0.000329714819071083 >> > _______________________________________________ > postgis-devel mailing list > postgis-devel@... > http://postgis.refractions.net/mailman/listinfo/postgis-devel > > > _______________________________________________ > postgis-devel mailing list > postgis-devel@... > http://postgis.refractions.net/mailman/listinfo/postgis-devel > postgis-devel mailing list postgis-devel@... http://postgis.refractions.net/mailman/listinfo/postgis-devel |
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Re: Sphere or Spheroid
by Paragon Corporation-2
::
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Ah okay, maybe that was why we decided against it last time. You should put
that in the notes. Anyrate even if we had GUC, I would still go with the multiple signatures as well since you may want different behavior for a specific query or when you are comparing numbers (you want both). -----Original Message----- From: postgis-devel-bounces@... [mailto:postgis-devel-bounces@...] On Behalf Of Paul Ramsey Sent: Friday, October 30, 2009 7:25 PM To: PostGIS Development Discussion Subject: Re: [postgis-devel] Sphere or Spheroid I did GUC research this morning and even did a GUC implementation! I don't think it makes this decision any less relevant, because frankly the default will rule 95% of the users. So choosing the "right" default is a good idea. Anyhow, on the GUC, a module-controlled GUC has an issue, in that the GUC can't exist until it's initialized by the module, and the initialization routine for the module is not executed until the first time a module function is called. So, running "SET geography.use_spheroid = true" will return an error if it's the first thing you do, but will work if you first do something like "SELECT ST_AsText('POINT(0 0)'::geography)" to force the module to load In all, a non-happy situation, so I have opted for function signatures for now, unless someone can tell me I should do otherwise. P. On Fri, Oct 30, 2009 at 4:10 PM, Paragon Corporation <lr@...> wrote: > I'm still dreaming of the GUC by the way. > http://trac.osgeo.org/postgis/ticket/267 to make this decision less > relevant. > > What is bool (will that mean True if you want measured in sphere?). > Regardless of what default you decide, that boolean has to mean the > same thing I think. (but I guess that's not too important) > > Thanks, > Regina > > -----Original Message----- > From: postgis-devel-bounces@... > [mailto:postgis-devel-bounces@...] On Behalf Of > Paul Ramsey > Sent: Friday, October 30, 2009 4:41 PM > To: PostGIS Development Discussion > Subject: Re: [postgis-devel] Sphere or Spheroid > > I should add that in general, the differences seem to be about 0.1% to > 0.2% for my Oregon test area. > > P. > > On Fri, Oct 30, 2009 at 1:39 PM, Paul Ramsey <pramsey@...> wrote: >> I am just now hooking up some spheroid calculations into SQL and the >> choice is here: what is the default return for ST_Distance(geog, >> geog) ? I have an extra signature ST_Distance(geog, geog, bool) which >> allows you to choose, *but* something has to be the default. So, slow >> and accurate or fast and not-quite-right? For reference, here's some >> test >> numbers: >> >> spheroid | sphere | diff | diff_pct >> ------------------+------------------+----------------------+-------- >> ------------------+------------------+----------------------+- >> ------------------+------------------+----------------------+-------- >> ------------------+------------------+----------------------+- >> ------------------+------------------+----------------------+----- >> 14.1244075108035 | 14.1394160043876 | -0.0150084935841761 | >> -0.00106146488507862 >> 14.6266188748041 | 14.5910056309084 | 0.0356132438956287 | >> 0.00244076692151968 >> 20.7346086743544 | 20.7259709082645 | 0.00863776608995082 | >> 0.000416760504402065 >> 21.9682444424626 | 21.9811452394388 | -0.0129007969762469 | >> -0.000586902858596291 >> 23.7383733187578 | 23.7519404190066 | -0.0135671002487641 | >> -0.000571199658193295 >> 24.71417232105 | 24.6751858115921 | 0.0389865094578177 | >> 0.00157998848541607 >> 26.060846145618 | 25.9957171978245 | 0.0651289477934469 | >> 0.00250537222334829 >> 29.1593418185795 | 29.0828389449609 | 0.0765028736186224 | >> 0.00263051601542076 >> 30.4726043383638 | 30.407477679772 | 0.0651266585918009 | >> 0.00214179746434954 >> 33.3089494734479 | 33.2231927324098 | 0.085756741038054 | >> 0.00258123118174602 >> 54.5278744382593 | 54.5740236709768 | -0.0461492327175321 | >> -0.000845626355054244 >> 56.6270596077484 | 56.4794616931023 | 0.147597914646141 | >> 0.00261330243280571 >> 58.0564235524421 | 57.9072919817022 | 0.149131570739875 | >> 0.00257535045477517 >> 61.5962238336604 | 61.6609971505153 | -0.0647733168549323 | >> -0.00105047468980788 >> 61.7015675105702 | 61.5433341315128 | 0.158233379057449 | >> 0.00257108883180295 >> 67.6094786823676 | 67.4707740811243 | 0.138704601243305 | >> 0.00205577308297266 >> 68.2569872101138 | 68.0830690889332 | 0.173918121180577 | >> 0.00255449884248604 >> 68.4943435865133 | 68.5554249222873 | -0.0610813357739914 | >> -0.000890977422184046 >> 68.5746705524887 | 68.4885568487924 | 0.0861137036962845 | >> 0.00125734440406453 >> 68.6758026445452 | 68.7123761613873 | -0.0365735168421395 | >> -0.000532269714501474 >> 73.4229241308488 | 73.4212994751178 | 0.00162465573099269 | >> 2.21278531244639e-05 >> 79.4484754792361 | 79.4536134385929 | -0.00513795935687256 | >> -6.46661509088383e-05 >> 85.4392924899187 | 85.3402382287158 | 0.0990542612029799 | >> 0.00116069820355446 >> 85.4539811995932 | 85.3919394786419 | 0.0620417209512425 | >> 0.00072655242789936 >> 93.5788665631846 | 93.4985937971677 | 0.0802727660169325 | >> 0.000858545169043645 >> 96.3199573238008 | 96.1797387047942 | 0.14021861900666 | >> 0.00145788105577033 >> 101.328501281213 | 101.062654489096 | 0.265846792116648 | >> 0.00263051463926598 >> 101.649559586565 | 101.502533562595 | 0.14702602397027 | >> 0.00144849609965254 >> 108.809850830453 | 108.894277925073 | -0.0844270946195422 | >> -0.000775312497848917 >> 109.397307465226 | 109.316521134613 | 0.0807863306121561 | >> 0.000739013003466101 >> 110.654864554623 | 110.763015546595 | -0.108150991971058 | >> -0.000976417908426867 >> 113.60376179349 | 113.561772904965 | 0.0419888885251396 | >> 0.000369744919007898 >> 114.121155128581 | 113.828085749691 | 0.293069378889427 | >> 0.00257466667351227 >> 114.310532244975 | 114.431988777869 | -0.121456532893603 | >> -0.00106138619271374 >> 115.797340494535 | 115.877511025684 | -0.0801705311490082 | >> -0.000691855826375479 >> 116.509315790761 | 116.204507950436 | 0.304807840325097 | >> 0.00262302939620126 >> 116.944936442573 | 116.776885086999 | 0.168051355574235 | >> 0.00143908064895751 >> 118.802848975488 | 118.599760910854 | 0.203088064634358 | >> 0.00171238173732078 >> 124.752683002401 | 124.793829377275 | -0.0411463748743159 | >> -0.000329714819071083 >> > _______________________________________________ > postgis-devel mailing list > postgis-devel@... > http://postgis.refractions.net/mailman/listinfo/postgis-devel > > > _______________________________________________ > postgis-devel mailing list > postgis-devel@... > http://postgis.refractions.net/mailman/listinfo/postgis-devel > postgis-devel mailing list postgis-devel@... http://postgis.refractions.net/mailman/listinfo/postgis-devel _______________________________________________ postgis-devel mailing list postgis-devel@... http://postgis.refractions.net/mailman/listinfo/postgis-devel |
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Re: Sphere or Spheroid
by Paul Ramsey-3
::
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Oh, BTW, we could just as easily have a utility function
geography_set_spheroid(bool) that you can call from SQL that will manipulate the global variable. That's all that the SET command ends up doing in the end anyways. P. On Fri, Oct 30, 2009 at 4:29 PM, Paragon Corporation <lr@...> wrote: > Ah okay, maybe that was why we decided against it last time. You should put > that in the notes. Anyrate even if we had GUC, I would still go with the > multiple signatures as well since you may want different behavior for a > specific query or when you are comparing numbers (you want both). > > > > -----Original Message----- > From: postgis-devel-bounces@... > [mailto:postgis-devel-bounces@...] On Behalf Of Paul > Ramsey > Sent: Friday, October 30, 2009 7:25 PM > To: PostGIS Development Discussion > Subject: Re: [postgis-devel] Sphere or Spheroid > > I did GUC research this morning and even did a GUC implementation! I don't > think it makes this decision any less relevant, because frankly the default > will rule 95% of the users. So choosing the "right" > default is a good idea. > > Anyhow, on the GUC, a module-controlled GUC has an issue, in that the GUC > can't exist until it's initialized by the module, and the initialization > routine for the module is not executed until the first time a module > function is called. So, running "SET geography.use_spheroid = true" will > return an error if it's the first thing you do, but will work if you first > do something like "SELECT ST_AsText('POINT(0 0)'::geography)" to force the > module to load > > In all, a non-happy situation, so I have opted for function signatures for > now, unless someone can tell me I should do otherwise. > > P. > > On Fri, Oct 30, 2009 at 4:10 PM, Paragon Corporation <lr@...> wrote: >> I'm still dreaming of the GUC by the way. >> http://trac.osgeo.org/postgis/ticket/267 to make this decision less >> relevant. > > >> >> What is bool (will that mean True if you want measured in sphere?). >> Regardless of what default you decide, that boolean has to mean the >> same thing I think. (but I guess that's not too important) >> >> Thanks, >> Regina >> >> -----Original Message----- >> From: postgis-devel-bounces@... >> [mailto:postgis-devel-bounces@...] On Behalf Of >> Paul Ramsey >> Sent: Friday, October 30, 2009 4:41 PM >> To: PostGIS Development Discussion >> Subject: Re: [postgis-devel] Sphere or Spheroid >> >> I should add that in general, the differences seem to be about 0.1% to >> 0.2% for my Oregon test area. >> >> P. >> >> On Fri, Oct 30, 2009 at 1:39 PM, Paul Ramsey <pramsey@...> wrote: >>> I am just now hooking up some spheroid calculations into SQL and the >>> choice is here: what is the default return for ST_Distance(geog, >>> geog) ? I have an extra signature ST_Distance(geog, geog, bool) which >>> allows you to choose, *but* something has to be the default. So, slow >>> and accurate or fast and not-quite-right? For reference, here's some >>> test >>> numbers: >>> >>> spheroid | sphere | diff | diff_pct >>> ------------------+------------------+----------------------+-------- >>> ------------------+------------------+----------------------+- >>> ------------------+------------------+----------------------+-------- >>> ------------------+------------------+----------------------+- >>> ------------------+------------------+----------------------+----- >>> 14.1244075108035 | 14.1394160043876 | -0.0150084935841761 | >>> -0.00106146488507862 >>> 14.6266188748041 | 14.5910056309084 | 0.0356132438956287 | >>> 0.00244076692151968 >>> 20.7346086743544 | 20.7259709082645 | 0.00863776608995082 | >>> 0.000416760504402065 >>> 21.9682444424626 | 21.9811452394388 | -0.0129007969762469 | >>> -0.000586902858596291 >>> 23.7383733187578 | 23.7519404190066 | -0.0135671002487641 | >>> -0.000571199658193295 >>> 24.71417232105 | 24.6751858115921 | 0.0389865094578177 | >>> 0.00157998848541607 >>> 26.060846145618 | 25.9957171978245 | 0.0651289477934469 | >>> 0.00250537222334829 >>> 29.1593418185795 | 29.0828389449609 | 0.0765028736186224 | >>> 0.00263051601542076 >>> 30.4726043383638 | 30.407477679772 | 0.0651266585918009 | >>> 0.00214179746434954 >>> 33.3089494734479 | 33.2231927324098 | 0.085756741038054 | >>> 0.00258123118174602 >>> 54.5278744382593 | 54.5740236709768 | -0.0461492327175321 | >>> -0.000845626355054244 >>> 56.6270596077484 | 56.4794616931023 | 0.147597914646141 | >>> 0.00261330243280571 >>> 58.0564235524421 | 57.9072919817022 | 0.149131570739875 | >>> 0.00257535045477517 >>> 61.5962238336604 | 61.6609971505153 | -0.0647733168549323 | >>> -0.00105047468980788 >>> 61.7015675105702 | 61.5433341315128 | 0.158233379057449 | >>> 0.00257108883180295 >>> 67.6094786823676 | 67.4707740811243 | 0.138704601243305 | >>> 0.00205577308297266 >>> 68.2569872101138 | 68.0830690889332 | 0.173918121180577 | >>> 0.00255449884248604 >>> 68.4943435865133 | 68.5554249222873 | -0.0610813357739914 | >>> -0.000890977422184046 >>> 68.5746705524887 | 68.4885568487924 | 0.0861137036962845 | >>> 0.00125734440406453 >>> 68.6758026445452 | 68.7123761613873 | -0.0365735168421395 | >>> -0.000532269714501474 >>> 73.4229241308488 | 73.4212994751178 | 0.00162465573099269 | >>> 2.21278531244639e-05 >>> 79.4484754792361 | 79.4536134385929 | -0.00513795935687256 | >>> -6.46661509088383e-05 >>> 85.4392924899187 | 85.3402382287158 | 0.0990542612029799 | >>> 0.00116069820355446 >>> 85.4539811995932 | 85.3919394786419 | 0.0620417209512425 | >>> 0.00072655242789936 >>> 93.5788665631846 | 93.4985937971677 | 0.0802727660169325 | >>> 0.000858545169043645 >>> 96.3199573238008 | 96.1797387047942 | 0.14021861900666 | >>> 0.00145788105577033 >>> 101.328501281213 | 101.062654489096 | 0.265846792116648 | >>> 0.00263051463926598 >>> 101.649559586565 | 101.502533562595 | 0.14702602397027 | >>> 0.00144849609965254 >>> 108.809850830453 | 108.894277925073 | -0.0844270946195422 | >>> -0.000775312497848917 >>> 109.397307465226 | 109.316521134613 | 0.0807863306121561 | >>> 0.000739013003466101 >>> 110.654864554623 | 110.763015546595 | -0.108150991971058 | >>> -0.000976417908426867 >>> 113.60376179349 | 113.561772904965 | 0.0419888885251396 | >>> 0.000369744919007898 >>> 114.121155128581 | 113.828085749691 | 0.293069378889427 | >>> 0.00257466667351227 >>> 114.310532244975 | 114.431988777869 | -0.121456532893603 | >>> -0.00106138619271374 >>> 115.797340494535 | 115.877511025684 | -0.0801705311490082 | >>> -0.000691855826375479 >>> 116.509315790761 | 116.204507950436 | 0.304807840325097 | >>> 0.00262302939620126 >>> 116.944936442573 | 116.776885086999 | 0.168051355574235 | >>> 0.00143908064895751 >>> 118.802848975488 | 118.599760910854 | 0.203088064634358 | >>> 0.00171238173732078 >>> 124.752683002401 | 124.793829377275 | -0.0411463748743159 | >>> -0.000329714819071083 >>> >> _______________________________________________ >> postgis-devel mailing list >> postgis-devel@... >> http://postgis.refractions.net/mailman/listinfo/postgis-devel >> >> >> _______________________________________________ >> postgis-devel mailing list >> postgis-devel@... >> http://postgis.refractions.net/mailman/listinfo/postgis-devel >> > _______________________________________________ > postgis-devel mailing list > postgis-devel@... > http://postgis.refractions.net/mailman/listinfo/postgis-devel > > > _______________________________________________ > postgis-devel mailing list > postgis-devel@... > http://postgis.refractions.net/mailman/listinfo/postgis-devel > postgis-devel mailing list postgis-devel@... http://postgis.refractions.net/mailman/listinfo/postgis-devel |
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Re: Sphere or Spheroid
by Paragon Corporation-2
::
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The choice of default sphere vs. spheroid is probably something we should ask the general PostGIS users group so cc'ing them since more people frequent that list that would have strong opinions on this subject. So question folks -- is which do you prefer as default behavior for new geography data type faster sphere calculation (with 0.05% - 1% margin error) (I vaguely recall that's what my studies suggested around the globe compared to UTM) or slower more accurate spheroid calculation Keep in mind -- this is just default behavior without an extra arg to the functions, you can use both in your work. details of current functions below http://www.postgis.org/documentation/manual-svn/ch08.html#PostGIS_GeographyF unctions Thanks, Regina -----Original Message----- From: postgis-devel-bounces@... [mailto:postgis-devel-bounces@...] On Behalf Of Paul Ramsey Sent: Friday, October 30, 2009 7:41 PM To: PostGIS Development Discussion Subject: Re: [postgis-devel] Sphere or Spheroid Oh, BTW, we could just as easily have a utility function geography_set_spheroid(bool) that you can call from SQL that will manipulate the global variable. That's all that the SET command ends up doing in the end anyways. P. On Fri, Oct 30, 2009 at 4:29 PM, Paragon Corporation <lr@...> wrote: > Ah okay, maybe that was why we decided against it last time. You > should put that in the notes. Anyrate even if we had GUC, I would > still go with the multiple signatures as well since you may want > different behavior for a specific query or when you are comparing numbers (you want both). > > > > -----Original Message----- > From: postgis-devel-bounces@... > [mailto:postgis-devel-bounces@...] On Behalf Of > Paul Ramsey > Sent: Friday, October 30, 2009 7:25 PM > To: PostGIS Development Discussion > Subject: Re: [postgis-devel] Sphere or Spheroid > > I did GUC research this morning and even did a GUC implementation! I > don't think it makes this decision any less relevant, because frankly > the default will rule 95% of the users. So choosing the "right" > default is a good idea. > > Anyhow, on the GUC, a module-controlled GUC has an issue, in that the > GUC can't exist until it's initialized by the module, and the > initialization routine for the module is not executed until the first > time a module function is called. So, running "SET > geography.use_spheroid = true" will return an error if it's the first > thing you do, but will work if you first do something like "SELECT > ST_AsText('POINT(0 0)'::geography)" to force the module to load > > In all, a non-happy situation, so I have opted for function signatures > for now, unless someone can tell me I should do otherwise. > > P. > > On Fri, Oct 30, 2009 at 4:10 PM, Paragon Corporation <lr@...> wrote: >> I'm still dreaming of the GUC by the way. >> http://trac.osgeo.org/postgis/ticket/267 to make this decision less >> relevant. > > >> >> What is bool (will that mean True if you want measured in sphere?). >> Regardless of what default you decide, that boolean has to mean the >> same thing I think. (but I guess that's not too important) >> >> Thanks, >> Regina >> >> -----Original Message----- >> From: postgis-devel-bounces@... >> [mailto:postgis-devel-bounces@...] On Behalf Of >> Paul Ramsey >> Sent: Friday, October 30, 2009 4:41 PM >> To: PostGIS Development Discussion >> Subject: Re: [postgis-devel] Sphere or Spheroid >> >> I should add that in general, the differences seem to be about 0.1% >> to 0.2% for my Oregon test area. >> >> P. >> >> On Fri, Oct 30, 2009 at 1:39 PM, Paul Ramsey <pramsey@...> wrote: >>> I am just now hooking up some spheroid calculations into SQL and the >>> choice is here: what is the default return for ST_Distance(geog, >>> geog) ? I have an extra signature ST_Distance(geog, geog, bool) >>> which allows you to choose, *but* something has to be the default. >>> So, slow and accurate or fast and not-quite-right? For reference, >>> here's some test >>> numbers: >>> >>> spheroid | sphere | diff | >>> diff_pct >>> ------------------+------------------+----------------------+------- >>> ------------------+------------------+----------------------+- >>> ------------------+------------------+----------------------+- >>> ------------------+------------------+----------------------+------- >>> ------------------+------------------+----------------------+- >>> ------------------+------------------+----------------------+- >>> ------------------+------------------+----------------------+----- >>> 14.1244075108035 | 14.1394160043876 | -0.0150084935841761 | >>> -0.00106146488507862 >>> 14.6266188748041 | 14.5910056309084 | 0.0356132438956287 | >>> 0.00244076692151968 >>> 20.7346086743544 | 20.7259709082645 | 0.00863776608995082 | >>> 0.000416760504402065 >>> 21.9682444424626 | 21.9811452394388 | -0.0129007969762469 | >>> -0.000586902858596291 >>> 23.7383733187578 | 23.7519404190066 | -0.0135671002487641 | >>> -0.000571199658193295 >>> 24.71417232105 | 24.6751858115921 | 0.0389865094578177 | >>> 0.00157998848541607 >>> 26.060846145618 | 25.9957171978245 | 0.0651289477934469 | >>> 0.00250537222334829 >>> 29.1593418185795 | 29.0828389449609 | 0.0765028736186224 | >>> 0.00263051601542076 >>> 30.4726043383638 | 30.407477679772 | 0.0651266585918009 | >>> 0.00214179746434954 >>> 33.3089494734479 | 33.2231927324098 | 0.085756741038054 | >>> 0.00258123118174602 >>> 54.5278744382593 | 54.5740236709768 | -0.0461492327175321 | >>> -0.000845626355054244 >>> 56.6270596077484 | 56.4794616931023 | 0.147597914646141 | >>> 0.00261330243280571 >>> 58.0564235524421 | 57.9072919817022 | 0.149131570739875 | >>> 0.00257535045477517 >>> 61.5962238336604 | 61.6609971505153 | -0.0647733168549323 | >>> -0.00105047468980788 >>> 61.7015675105702 | 61.5433341315128 | 0.158233379057449 | >>> 0.00257108883180295 >>> 67.6094786823676 | 67.4707740811243 | 0.138704601243305 | >>> 0.00205577308297266 >>> 68.2569872101138 | 68.0830690889332 | 0.173918121180577 | >>> 0.00255449884248604 >>> 68.4943435865133 | 68.5554249222873 | -0.0610813357739914 | >>> -0.000890977422184046 >>> 68.5746705524887 | 68.4885568487924 | 0.0861137036962845 | >>> 0.00125734440406453 >>> 68.6758026445452 | 68.7123761613873 | -0.0365735168421395 | >>> -0.000532269714501474 >>> 73.4229241308488 | 73.4212994751178 | 0.00162465573099269 | >>> 2.21278531244639e-05 >>> 79.4484754792361 | 79.4536134385929 | -0.00513795935687256 | >>> -6.46661509088383e-05 >>> 85.4392924899187 | 85.3402382287158 | 0.0990542612029799 | >>> 0.00116069820355446 >>> 85.4539811995932 | 85.3919394786419 | 0.0620417209512425 | >>> 0.00072655242789936 >>> 93.5788665631846 | 93.4985937971677 | 0.0802727660169325 | >>> 0.000858545169043645 >>> 96.3199573238008 | 96.1797387047942 | 0.14021861900666 | >>> 0.00145788105577033 >>> 101.328501281213 | 101.062654489096 | 0.265846792116648 | >>> 0.00263051463926598 >>> 101.649559586565 | 101.502533562595 | 0.14702602397027 | >>> 0.00144849609965254 >>> 108.809850830453 | 108.894277925073 | -0.0844270946195422 | >>> -0.000775312497848917 >>> 109.397307465226 | 109.316521134613 | 0.0807863306121561 | >>> 0.000739013003466101 >>> 110.654864554623 | 110.763015546595 | -0.108150991971058 | >>> -0.000976417908426867 >>> 113.60376179349 | 113.561772904965 | 0.0419888885251396 | >>> 0.000369744919007898 >>> 114.121155128581 | 113.828085749691 | 0.293069378889427 | >>> 0.00257466667351227 >>> 114.310532244975 | 114.431988777869 | -0.121456532893603 | >>> -0.00106138619271374 >>> 115.797340494535 | 115.877511025684 | -0.0801705311490082 | >>> -0.000691855826375479 >>> 116.509315790761 | 116.204507950436 | 0.304807840325097 | >>> 0.00262302939620126 >>> 116.944936442573 | 116.776885086999 | 0.168051355574235 | >>> 0.00143908064895751 >>> 118.802848975488 | 118.599760910854 | 0.203088064634358 | >>> 0.00171238173732078 >>> 124.752683002401 | 124.793829377275 | -0.0411463748743159 | >>> -0.000329714819071083 >>> >> _______________________________________________ >> postgis-devel mailing list >> postgis-devel@... >> http://postgis.refractions.net/mailman/listinfo/postgis-devel >> >> >> _______________________________________________ >> postgis-devel mailing list >> postgis-devel@... >> http://postgis.refractions.net/mailman/listinfo/postgis-devel >> > _______________________________________________ > postgis-devel mailing list > postgis-devel@... > http://postgis.refractions.net/mailman/listinfo/postgis-devel > > > _______________________________________________ > postgis-devel mailing list > postgis-devel@... > http://postgis.refractions.net/mailman/listinfo/postgis-devel > postgis-devel mailing list postgis-devel@... http://postgis.refractions.net/mailman/listinfo/postgis-devel _______________________________________________ postgis-devel mailing list postgis-devel@... http://postgis.refractions.net/mailman/listinfo/postgis-devel |
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Re: Sphere or Spheroid
by Paul Ramsey-3
::
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It looks like, for basic usage, the performance difference is
relatively small (which is probably because most of the calculations are on the sphere, only the last few are on the spheroid). For cases line point/point tests the differences will be most stark. But here's a medium sized spatial join on line/polygon. geog=# select count(*) from buildings b, streets s where st_dwithin(b.geog, s.geog, 50000) and s.gid = 100; count -------- 144783 (1 row) Time: 6185.445 ms geog=# select count(*) from buildings b, streets s where st_dwithin(b.geog, s.geog, 50000, false) and s.gid = 100; count -------- 144795 (1 row) Time: 5879.593 ms geog=# On Fri, Oct 30, 2009 at 4:48 PM, Paragon Corporation <lr@...> wrote: > > The choice of default sphere vs. spheroid is probably something we should > ask the general PostGIS users group so cc'ing them since more people > frequent that list that would have strong opinions on this subject. > > So question folks -- is which do you prefer as default behavior for new > geography data type > > faster sphere calculation (with 0.05% - 1% margin error) (I vaguely recall > that's what my studies suggested around the globe compared to UTM) > > or > slower more accurate spheroid calculation > > Keep in mind -- this is just default behavior without an extra arg to the > functions, you can use both in your work. > > details of current functions below > > http://www.postgis.org/documentation/manual-svn/ch08.html#PostGIS_GeographyF > unctions > > Thanks, > Regina > -----Original Message----- > From: postgis-devel-bounces@... > [mailto:postgis-devel-bounces@...] On Behalf Of Paul > Ramsey > Sent: Friday, October 30, 2009 7:41 PM > To: PostGIS Development Discussion > Subject: Re: [postgis-devel] Sphere or Spheroid > > Oh, BTW, we could just as easily have a utility function > geography_set_spheroid(bool) that you can call from SQL that will manipulate > the global variable. That's all that the SET command ends up doing in the > end anyways. > > P. > > On Fri, Oct 30, 2009 at 4:29 PM, Paragon Corporation <lr@...> wrote: >> Ah okay, maybe that was why we decided against it last time. You >> should put that in the notes. Anyrate even if we had GUC, I would >> still go with the multiple signatures as well since you may want >> different behavior for a specific query or when you are comparing numbers > (you want both). >> >> >> >> -----Original Message----- >> From: postgis-devel-bounces@... >> [mailto:postgis-devel-bounces@...] On Behalf Of >> Paul Ramsey >> Sent: Friday, October 30, 2009 7:25 PM >> To: PostGIS Development Discussion >> Subject: Re: [postgis-devel] Sphere or Spheroid >> >> I did GUC research this morning and even did a GUC implementation! I >> don't think it makes this decision any less relevant, because frankly >> the default will rule 95% of the users. So choosing the "right" >> default is a good idea. >> >> Anyhow, on the GUC, a module-controlled GUC has an issue, in that the >> GUC can't exist until it's initialized by the module, and the >> initialization routine for the module is not executed until the first >> time a module function is called. So, running "SET >> geography.use_spheroid = true" will return an error if it's the first >> thing you do, but will work if you first do something like "SELECT >> ST_AsText('POINT(0 0)'::geography)" to force the module to load >> >> In all, a non-happy situation, so I have opted for function signatures >> for now, unless someone can tell me I should do otherwise. >> >> P. >> >> On Fri, Oct 30, 2009 at 4:10 PM, Paragon Corporation <lr@...> wrote: >>> I'm still dreaming of the GUC by the way. >>> http://trac.osgeo.org/postgis/ticket/267 to make this decision less >>> relevant. >> >> >>> >>> What is bool (will that mean True if you want measured in sphere?). >>> Regardless of what default you decide, that boolean has to mean the >>> same thing I think. (but I guess that's not too important) >>> >>> Thanks, >>> Regina >>> >>> -----Original Message----- >>> From: postgis-devel-bounces@... >>> [mailto:postgis-devel-bounces@...] On Behalf Of >>> Paul Ramsey >>> Sent: Friday, October 30, 2009 4:41 PM >>> To: PostGIS Development Discussion >>> Subject: Re: [postgis-devel] Sphere or Spheroid >>> >>> I should add that in general, the differences seem to be about 0.1% >>> to 0.2% for my Oregon test area. >>> >>> P. >>> >>> On Fri, Oct 30, 2009 at 1:39 PM, Paul Ramsey <pramsey@...> wrote: >>>> I am just now hooking up some spheroid calculations into SQL and the >>>> choice is here: what is the default return for ST_Distance(geog, >>>> geog) ? I have an extra signature ST_Distance(geog, geog, bool) >>>> which allows you to choose, *but* something has to be the default. >>>> So, slow and accurate or fast and not-quite-right? For reference, >>>> here's some test >>>> numbers: >>>> >>>> spheroid | sphere | diff | >>>> diff_pct >>>> ------------------+------------------+----------------------+------- >>>> ------------------+------------------+----------------------+- >>>> ------------------+------------------+----------------------+- >>>> ------------------+------------------+----------------------+------- >>>> ------------------+------------------+----------------------+- >>>> ------------------+------------------+----------------------+- >>>> ------------------+------------------+----------------------+----- >>>> 14.1244075108035 | 14.1394160043876 | -0.0150084935841761 | >>>> -0.00106146488507862 >>>> 14.6266188748041 | 14.5910056309084 | 0.0356132438956287 | >>>> 0.00244076692151968 >>>> 20.7346086743544 | 20.7259709082645 | 0.00863776608995082 | >>>> 0.000416760504402065 >>>> 21.9682444424626 | 21.9811452394388 | -0.0129007969762469 | >>>> -0.000586902858596291 >>>> 23.7383733187578 | 23.7519404190066 | -0.0135671002487641 | >>>> -0.000571199658193295 >>>> 24.71417232105 | 24.6751858115921 | 0.0389865094578177 | >>>> 0.00157998848541607 >>>> 26.060846145618 | 25.9957171978245 | 0.0651289477934469 | >>>> 0.00250537222334829 >>>> 29.1593418185795 | 29.0828389449609 | 0.0765028736186224 | >>>> 0.00263051601542076 >>>> 30.4726043383638 | 30.407477679772 | 0.0651266585918009 | >>>> 0.00214179746434954 >>>> 33.3089494734479 | 33.2231927324098 | 0.085756741038054 | >>>> 0.00258123118174602 >>>> 54.5278744382593 | 54.5740236709768 | -0.0461492327175321 | >>>> -0.000845626355054244 >>>> 56.6270596077484 | 56.4794616931023 | 0.147597914646141 | >>>> 0.00261330243280571 >>>> 58.0564235524421 | 57.9072919817022 | 0.149131570739875 | >>>> 0.00257535045477517 >>>> 61.5962238336604 | 61.6609971505153 | -0.0647733168549323 | >>>> -0.00105047468980788 >>>> 61.7015675105702 | 61.5433341315128 | 0.158233379057449 | >>>> 0.00257108883180295 >>>> 67.6094786823676 | 67.4707740811243 | 0.138704601243305 | >>>> 0.00205577308297266 >>>> 68.2569872101138 | 68.0830690889332 | 0.173918121180577 | >>>> 0.00255449884248604 >>>> 68.4943435865133 | 68.5554249222873 | -0.0610813357739914 | >>>> -0.000890977422184046 >>>> 68.5746705524887 | 68.4885568487924 | 0.0861137036962845 | >>>> 0.00125734440406453 >>>> 68.6758026445452 | 68.7123761613873 | -0.0365735168421395 | >>>> -0.000532269714501474 >>>> 73.4229241308488 | 73.4212994751178 | 0.00162465573099269 | >>>> 2.21278531244639e-05 >>>> 79.4484754792361 | 79.4536134385929 | -0.00513795935687256 | >>>> -6.46661509088383e-05 >>>> 85.4392924899187 | 85.3402382287158 | 0.0990542612029799 | >>>> 0.00116069820355446 >>>> 85.4539811995932 | 85.3919394786419 | 0.0620417209512425 | >>>> 0.00072655242789936 >>>> 93.5788665631846 | 93.4985937971677 | 0.0802727660169325 | >>>> 0.000858545169043645 >>>> 96.3199573238008 | 96.1797387047942 | 0.14021861900666 | >>>> 0.00145788105577033 >>>> 101.328501281213 | 101.062654489096 | 0.265846792116648 | >>>> 0.00263051463926598 >>>> 101.649559586565 | 101.502533562595 | 0.14702602397027 | >>>> 0.00144849609965254 >>>> 108.809850830453 | 108.894277925073 | -0.0844270946195422 | >>>> -0.000775312497848917 >>>> 109.397307465226 | 109.316521134613 | 0.0807863306121561 | >>>> 0.000739013003466101 >>>> 110.654864554623 | 110.763015546595 | -0.108150991971058 | >>>> -0.000976417908426867 >>>> 113.60376179349 | 113.561772904965 | 0.0419888885251396 | >>>> 0.000369744919007898 >>>> 114.121155128581 | 113.828085749691 | 0.293069378889427 | >>>> 0.00257466667351227 >>>> 114.310532244975 | 114.431988777869 | -0.121456532893603 | >>>> -0.00106138619271374 >>>> 115.797340494535 | 115.877511025684 | -0.0801705311490082 | >>>> -0.000691855826375479 >>>> 116.509315790761 | 116.204507950436 | 0.304807840325097 | >>>> 0.00262302939620126 >>>> 116.944936442573 | 116.776885086999 | 0.168051355574235 | >>>> 0.00143908064895751 >>>> 118.802848975488 | 118.599760910854 | 0.203088064634358 | >>>> 0.00171238173732078 >>>> 124.752683002401 | 124.793829377275 | -0.0411463748743159 | >>>> -0.000329714819071083 >>>> >>> _______________________________________________ >>> postgis-devel mailing list >>> postgis-devel@... >>> http://postgis.refractions.net/mailman/listinfo/postgis-devel >>> >>> >>> _______________________________________________ >>> postgis-devel mailing list >>> postgis-devel@... >>> http://postgis.refractions.net/mailman/listinfo/postgis-devel >>> >> _______________________________________________ >> postgis-devel mailing list >> postgis-devel@... >> http://postgis.refractions.net/mailman/listinfo/postgis-devel >> >> >> _______________________________________________ >> postgis-devel mailing list >> postgis-devel@... >> http://postgis.refractions.net/mailman/listinfo/postgis-devel >> > _______________________________________________ > postgis-devel mailing list > postgis-devel@... > http://postgis.refractions.net/mailman/listinfo/postgis-devel > > > 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