[gdal-dev] Re: gdal_rasterize 1.8.0 options
On 05/02/2011 00:06, Even Rouault wrote: Unrelated with GDAL 1.8.0. The issue was that the transformation between OGC WKT and ESRI WKT didn't handle well the Oblique Stereographic projection. Fixed in trunk in http://trac.osgeo.org/gdal/changeset/21627 Even, Once upon a time I opened http://trac.osgeo.org/gdal/ticket/2869, thinking that the reported issue could be fixed with a simple remapping between Double_Stereographic and Oblique_Stereographic projections. Could you perhaps have a look at this 2-year old ticket? Thanks in advance, Hermann ___ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
[gdal-dev] Re: gdal_rasterize 1.8.0 options
Le samedi 05 février 2011 12:49:15, Hermann Peifer a écrit : > On 05/02/2011 00:06, Even Rouault wrote: > > Unrelated with GDAL 1.8.0. The issue was that the transformation between > > OGC WKT and ESRI WKT didn't handle well the Oblique Stereographic > > projection. Fixed in trunk in http://trac.osgeo.org/gdal/changeset/21627 > > Even, > > Once upon a time I opened http://trac.osgeo.org/gdal/ticket/2869, > thinking that the reported issue could be fixed with a simple remapping > between Double_Stereographic and Oblique_Stereographic projections. > > Could you perhaps have a look at this 2-year old ticket? > > Thanks in advance, Hermann Hermann, I've just had a look, but not being neither Dutch nor a specialist of (stereographic) projections, I don't feel competent enough to do any action on it. Those tickets plus the reading of http://udig.refractions.net/files/docs/api- geotools/org/geotools/referencing/operation/projection/Stereographic.html make me deeply confused and wondering if r21627 was really appropriate. ___ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
[gdal-dev] Re: gdal_rasterize 1.8.0 options
On 05/02/2011 13:12, Even Rouault wrote: I've just had a look, but not being neither Dutch nor a specialist of (stereographic) projections, I don't feel competent enough to do any action on it. Those tickets plus the reading of http://udig.refractions.net/files/docs/api- geotools/org/geotools/referencing/operation/projection/Stereographic.html make me deeply confused and wondering if r21627 was really appropriate. Hmm. This page confirms what I mentioned in ticket #2869: "Double_Stereographic" is simply the ESRI alias of "Oblique_Stereographic" (EPSG code 9809). About r21627: I am afraid I do not understand enough about the inner workings of GDAL/OGR to make a judgement about whether this change was appropriate or not. But by the end of the day and from what I remember when looking somewhat deeper into the issue, about 2 years ago: there is one stereographic projection (known as "the USGS formula" or "the approach given by Snyder") which translates into +proj=stere, and there is the other "Double_Stereographic", aka "Oblique_Stereographic" which is expected to end up as +proj=sterea. Hermann ___ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
Re: [gdal-dev] Re: gdal_rasterize 1.8.0 options
Even, Hermann might be right. From reading several sources: http://gge.unb.ca/Pubs/TR46.pdf http://www.manifold.net/doc/double_stereographic.htm it seems that double stereographic is oblique stereographic as long as the origin is non-equatorial or non-polar. The actual denomination "Double Stereographic" seems to be a ESRI by-product that refers to "Oblique Stereographic". However, ESRI's own descriptions of these projections are, at best, vague. -marius On Sat, 2011-02-05 at 13:12 +0100, Even Rouault wrote: > Le samedi 05 février 2011 12:49:15, Hermann Peifer a écrit : > > On 05/02/2011 00:06, Even Rouault wrote: > > > Unrelated with GDAL 1.8.0. The issue was that the transformation between > > > OGC WKT and ESRI WKT didn't handle well the Oblique Stereographic > > > projection. Fixed in trunk in http://trac.osgeo.org/gdal/changeset/21627 > > > > Even, > > > > Once upon a time I opened http://trac.osgeo.org/gdal/ticket/2869, > > thinking that the reported issue could be fixed with a simple remapping > > between Double_Stereographic and Oblique_Stereographic projections. > > > > Could you perhaps have a look at this 2-year old ticket? > > > > Thanks in advance, Hermann > > Hermann, > > I've just had a look, but not being neither Dutch nor a specialist of > (stereographic) projections, I don't feel competent enough to do any action > on > it. Those tickets plus the reading of > http://udig.refractions.net/files/docs/api- > geotools/org/geotools/referencing/operation/projection/Stereographic.html > make > me deeply confused and wondering if r21627 was really appropriate. > ___ > gdal-dev mailing list > gdal-dev@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/gdal-dev > ___ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
Re: [gdal-dev] Re: gdal_rasterize 1.8.0 options
W dniu 05.02.2011 14:47, Hermann Peifer pisze: On 05/02/2011 13:12, Even Rouault wrote: I've just had a look, but not being neither Dutch nor a specialist of (stereographic) projections, I don't feel competent enough to do any action on it. Those tickets plus the reading of http://udig.refractions.net/files/docs/api- geotools/org/geotools/referencing/operation/projection/Stereographic.html make me deeply confused and wondering if r21627 was really appropriate. Hmm. This page confirms what I mentioned in ticket #2869: "Double_Stereographic" is simply the ESRI alias of "Oblique_Stereographic" (EPSG code 9809). About r21627: I am afraid I do not understand enough about the inner workings of GDAL/OGR to make a judgement about whether this change was appropriate or not. But by the end of the day and from what I remember when looking somewhat deeper into the issue, about 2 years ago: there is one stereographic projection (known as "the USGS formula" or "the approach given by Snyder") which translates into +proj=stere, and there is the other "Double_Stereographic", aka "Oblique_Stereographic" which is expected to end up as +proj=sterea. I'm not an expert too, but Hermann findings are in accordance with my findings for Polish stereographic CRS (from over 5 years ago): http://lists.maptools.org/pipermail/proj/2005-March/001524.html The Polish CRSs which use +proj=sterea version of stereographic are 3120, 2172-2174, 3328. See also Gerald Evendeen's notes: http://lists.maptools.org/pipermail/proj/2005-March/001526.html Maciek -- Maciej Sieczka http://www.sieczka.org ___ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
Re: [gdal-dev] Re: gdal_rasterize 1.8.0 options
For the Dutch case: in 2005 the PROJ-definition for the Dutch national system (which uses "Double Stereographic") was changed from "stere" to "sterea". See the thread starting at: http://lists.osgeo.org/pipermail/gdal-dev/2005-November/007045.html. The thread refers to a bug ticket at http://bugzilla.remotesensing.org/show_bug.cgi?id=980, but that link doesn't exist anymore. Is there a place to put al the links on the stere-sterea subject together? In my experience, discussions about projection parameters tend to get fragmented, and even if a solution has been found, old errors tend to show up time and again. Sometimes, I can only find the solution in my private email archive. Jan On 2011-02-07 11:32, Maciej Sieczka wrote: W dniu 05.02.2011 14:47, Hermann Peifer pisze: On 05/02/2011 13:12, Even Rouault wrote: I've just had a look, but not being neither Dutch nor a specialist of (stereographic) projections, I don't feel competent enough to do any action on it. Those tickets plus the reading of http://udig.refractions.net/files/docs/api- geotools/org/geotools/referencing/operation/projection/Stereographic.html make me deeply confused and wondering if r21627 was really appropriate. Hmm. This page confirms what I mentioned in ticket #2869: "Double_Stereographic" is simply the ESRI alias of "Oblique_Stereographic" (EPSG code 9809). About r21627: I am afraid I do not understand enough about the inner workings of GDAL/OGR to make a judgement about whether this change was appropriate or not. But by the end of the day and from what I remember when looking somewhat deeper into the issue, about 2 years ago: there is one stereographic projection (known as "the USGS formula" or "the approach given by Snyder") which translates into +proj=stere, and there is the other "Double_Stereographic", aka "Oblique_Stereographic" which is expected to end up as +proj=sterea. I'm not an expert too, but Hermann findings are in accordance with my findings for Polish stereographic CRS (from over 5 years ago): http://lists.maptools.org/pipermail/proj/2005-March/001524.html The Polish CRSs which use +proj=sterea version of stereographic are 3120, 2172-2174, 3328. See also Gerald Evendeen's notes: http://lists.maptools.org/pipermail/proj/2005-March/001526.html Maciek ___ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
Re: [gdal-dev] Re: gdal_rasterize 1.8.0 options
I've kept out of this debate so far - partly waiting until I had my copy of Snyder's 'Working Manual' (USGS Professional Paper 1395) in front of me. I've also got ESRI's 'Understanding Map Projections' by Kennedy and Kopp (my copy is dated 2000; ESRI Press) to hand. I had a hazy memory that this was a complicated area ... as it indeed seems to be. According to Kennedy and Kopp, the ESRI Stereographic projection uses the ellipsoid directly, whilst the Double Stereographic projection takes the ellipsoid to a Gaussian sphere before calculating the planar form. According to Snyder (pp154-157) the basic Stereographic projection is an azimuthal conformal perspective projection on the sphere but only azimuthal conformal in the polar form on the ellipsoid, when it 'is not perspective'. There are also modified forms (Snyder p 203) that are not symmetrical and in which meridians and parallels are complex curves. Snyder provides separate formulae for the spherical and ellipsoidal forms, implying that the spherical form is not a simple special case of the ellipsoidal. In both Bugayevskiy & Snyder (1995, Map Projections: A Reference Manual, London: Taylor & Francis) and Yang, Snyder and Tobler (2000, Map Projection Transformation: Principles and Applications, London: Taylor & Francis) a "double" projection is defined as one in which the ellipsoidal form is first projected onto a sphere and then the sphere to planar form. They also separate the spherical and ellipsoidal forms for the stereographic formulae. This suggests that Kennedy & Kopp do give the detail necessary when they mention projection first onto the Gaussian sphere. I have not examined the code of GDAL, nor of Proj4, so do not know whether these have the facility to transform from ellipsoid to sphere to planar to replicate the 'double' or whether the spherical or ellipsoidal form is provided - let alone as to whether such a double method is supported. However, I suspect that Even is correct to surmise that the issue is not straightforward. Best wishes, Peter Maciej Sieczka wrote: W dniu 05.02.2011 14:47, Hermann Peifer pisze: On 05/02/2011 13:12, Even Rouault wrote: I've just had a look, but not being neither Dutch nor a specialist of (stereographic) projections, I don't feel competent enough to do any action on it. Those tickets plus the reading of http://udig.refractions.net/files/docs/api- geotools/org/geotools/referencing/operation/projection/Stereographic.html make me deeply confused and wondering if r21627 was really appropriate. Hmm. This page confirms what I mentioned in ticket #2869: "Double_Stereographic" is simply the ESRI alias of "Oblique_Stereographic" (EPSG code 9809). About r21627: I am afraid I do not understand enough about the inner workings of GDAL/OGR to make a judgement about whether this change was appropriate or not. But by the end of the day and from what I remember when looking somewhat deeper into the issue, about 2 years ago: there is one stereographic projection (known as "the USGS formula" or "the approach given by Snyder") which translates into +proj=stere, and there is the other "Double_Stereographic", aka "Oblique_Stereographic" which is expected to end up as +proj=sterea. I'm not an expert too, but Hermann findings are in accordance with my findings for Polish stereographic CRS (from over 5 years ago): http://lists.maptools.org/pipermail/proj/2005-March/001524.html The Polish CRSs which use +proj=sterea version of stereographic are 3120, 2172-2174, 3328. See also Gerald Evendeen's notes: http://lists.maptools.org/pipermail/proj/2005-March/001526.html Maciek -- Peter J Halls, GIS Advisor & Acting Team Leader Applications Support Group, Information Directorate, University of York Telephone: 01904 323806 Fax: 01904 323740 Snail mail: C/O IT Services, University of York, Heslington, York YO10 5DD This message has the status of a private and personal communication ___ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
Re: [gdal-dev] Re: gdal_rasterize 1.8.0 options
As far as the Dutch projection is concerned (EPSG:28992), Peter's summary is correct: it first projects the ellipsoid to the sphere and then projects the sphere stereographically to the plane. I don't know if that is the way PROJ4 computes the transformation, but I can garantee that using "sterea" as parameter gives correct results here. Jan On 2011-02-07 12:32, Peter J Halls wrote: I've kept out of this debate so far - partly waiting until I had my copy of Snyder's 'Working Manual' (USGS Professional Paper 1395) in front of me. I've also got ESRI's 'Understanding Map Projections' by Kennedy and Kopp (my copy is dated 2000; ESRI Press) to hand. I had a hazy memory that this was a complicated area ... as it indeed seems to be. According to Kennedy and Kopp, the ESRI Stereographic projection uses the ellipsoid directly, whilst the Double Stereographic projection takes the ellipsoid to a Gaussian sphere before calculating the planar form. According to Snyder (pp154-157) the basic Stereographic projection is an azimuthal conformal perspective projection on the sphere but only azimuthal conformal in the polar form on the ellipsoid, when it 'is not perspective'. There are also modified forms (Snyder p 203) that are not symmetrical and in which meridians and parallels are complex curves. Snyder provides separate formulae for the spherical and ellipsoidal forms, implying that the spherical form is not a simple special case of the ellipsoidal. In both Bugayevskiy & Snyder (1995, Map Projections: A Reference Manual, London: Taylor & Francis) and Yang, Snyder and Tobler (2000, Map Projection Transformation: Principles and Applications, London: Taylor & Francis) a "double" projection is defined as one in which the ellipsoidal form is first projected onto a sphere and then the sphere to planar form. They also separate the spherical and ellipsoidal forms for the stereographic formulae. This suggests that Kennedy & Kopp do give the detail necessary when they mention projection first onto the Gaussian sphere. I have not examined the code of GDAL, nor of Proj4, so do not know whether these have the facility to transform from ellipsoid to sphere to planar to replicate the 'double' or whether the spherical or ellipsoidal form is provided - let alone as to whether such a double method is supported. However, I suspect that Even is correct to surmise that the issue is not straightforward. Best wishes, Peter Maciej Sieczka wrote: W dniu 05.02.2011 14:47, Hermann Peifer pisze: On 05/02/2011 13:12, Even Rouault wrote: I've just had a look, but not being neither Dutch nor a specialist of (stereographic) projections, I don't feel competent enough to do any action on it. Those tickets plus the reading of http://udig.refractions.net/files/docs/api- geotools/org/geotools/referencing/operation/projection/Stereographic.html make me deeply confused and wondering if r21627 was really appropriate. Hmm. This page confirms what I mentioned in ticket #2869: "Double_Stereographic" is simply the ESRI alias of "Oblique_Stereographic" (EPSG code 9809). About r21627: I am afraid I do not understand enough about the inner workings of GDAL/OGR to make a judgement about whether this change was appropriate or not. But by the end of the day and from what I remember when looking somewhat deeper into the issue, about 2 years ago: there is one stereographic projection (known as "the USGS formula" or "the approach given by Snyder") which translates into +proj=stere, and there is the other "Double_Stereographic", aka "Oblique_Stereographic" which is expected to end up as +proj=sterea. I'm not an expert too, but Hermann findings are in accordance with my findings for Polish stereographic CRS (from over 5 years ago): http://lists.maptools.org/pipermail/proj/2005-March/001524.html The Polish CRSs which use +proj=sterea version of stereographic are 3120, 2172-2174, 3328. See also Gerald Evendeen's notes: http://lists.maptools.org/pipermail/proj/2005-March/001526.html Maciek ___ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
Re: [gdal-dev] Re: gdal_rasterize 1.8.0 options
On 11-02-07 06:25 AM, Jan Hartmann wrote: Is there a place to put al the links on the stere-sterea subject together? In my experience, discussions about projection parameters tend to get fragmented, and even if a solution has been found, old errors tend to show up time and again. Sometimes, I can only find the solution in my private email archive. Jan, I had been hoping to convert the topics at: http://www.remotesensing.org/geotiff/proj_list/ into Trac wiki topics so that anyone could easily update them. Perhaps the MetaCRS wiki would be more appropriate than the GeoTIFF one. If anyone was interested in taking that on as a task, I'd be happy to update the links accordingly. We could start by moving over the oblique stereographic discussion and updating it with the missing information. Best regards, -- ---+-- I set the clouds in motion - turn up | Frank Warmerdam, warmer...@pobox.com light and sound - activate the windows | http://pobox.com/~warmerdam and watch the world go round - Rush| Geospatial Programmer for Rent ___ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
Re: [gdal-dev] Re: gdal_rasterize 1.8.0 options
On 2011-02-07 15:45, Frank Warmerdam wrote: On 11-02-07 06:25 AM, Jan Hartmann wrote: Is there a place to put al the links on the stere-sterea subject together? In my experience, discussions about projection parameters tend to get fragmented, and even if a solution has been found, old errors tend to show up time and again. Sometimes, I can only find the solution in my private email archive. Jan, I had been hoping to convert the topics at: http://www.remotesensing.org/geotiff/proj_list/ into Trac wiki topics so that anyone could easily update them. Perhaps the MetaCRS wiki would be more appropriate than the GeoTIFF one. If anyone was interested in taking that on as a task, I'd be happy to update the links accordingly. We could start by moving over the oblique stereographic discussion and updating it with the missing information. OK Frank, I'll take up the two Dutch problems, sterea and the towgs84 conversion. You won't believe how much discussion I still see over here about things not fitting with Google Maps. It would be nice to have an authorative reference. Please say how I can help out. Jan ___ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
