Re: [Geoserver-users] Buffer error
Then your map is distorted, Google maps uses EPSG:3587 (or epsg:900913 if you are using old terms) and that is a web Mercator projection which has an increasing E-W distortion as you move away from the equator. The other possible issue is that depending on how you projected your point into a local CRS and then projected the buffer back to WGS there is a chance to introduce inaccuracies into the process. Unless you just guessed a degrees to metres conversion factor that seemed about right for one of your points? Anyway, on that map circular buffers should look stretched out like yours do. Ian De: Ian Turton <ijtur...@gmail.com> Enviado: segunda-feira, 23 de outubro de 2017 13:47 Para: Alexandre Barboza Cc: geoserver-users@lists.sourceforge.net Assunto: Re: [Geoserver-users] Buffer error Then your map is distorted, Google maps uses EPSG:3587 (or epsg:900913 if you are using old terms) and that is a web Mercator projection which has an increasing E-W distortion as you move away from the equator. The other possible issue is that depending on how you projected your point into a local CRS and then projected the buffer back to WGS there is a chance to introduce inaccuracies into the process. Unless you just guessed a degrees to metres conversion factor that seemed about right for one of your points? Anyway, on that map circular buffers should look stretched out like yours do. Ian On 23 October 2017 at 16:26, Alexandre Barboza <ambarb...@hotmail.com<mailto:ambarb...@hotmail.com>> wrote: Hi Ian Thanks for your answer! We are using EPSG 4326 projection, and display it on Google Maps API, always tiled. When we open it on QGIS the buffer size dos not is the same that we specified on X axis and Y axis. sample: when we do a buffer of 500 meters (radius) the x axis result about 450 meters and Y axis have 500 meters. On this url http://www.ide.emplasa.sp.gov.br/geoserver/emplasa/TESTE_BUFFER_GEOWGS84/wms? we did a buffer with distance of 500 meters using EPSG 4326 layer On our website the buffer url is http://www.ide.emplasa.sp.gov.br/geoserver/emplasa/LOCALIDADES_EMPLASA_SAUDE/wms?styles=SYS_SIMM_ESTILO_BUFFER_DINAMICO_THE_GEOM=polygonStrokecolor:003300;polygonFillcolor:FF;bufferSize:500_FILTER=NOME_MUNIC%20LIKE%20%27Diadema%27=WMS=1.1.1=GetMap=emplasa:LOCALIDADES_EMPLASA_SAUDE=image/png=false=true=EPSG:900913=-5190379.968676608,-2727273.1692150906,-5187933.9837714825,-2724827.184309963=256=256 De: Ian Turton <ijtur...@gmail.com<mailto:ijtur...@gmail.com>> Enviado: segunda-feira, 23 de outubro de 2017 12:49 Para: Alexandre Barboza Cc: geoserver-users@lists.sourceforge.net<mailto:geoserver-users@lists.sourceforge.net> Assunto: Re: [Geoserver-users] Buffer error TBH that looks like a projected (EPSG:3857) map to me, so I would expect some distortion. You probably don't want to use tiles for that layer either, or maybe experiment with gutters to see if that helps with the edge cases. Please show the actual request to the buffer process so we can test it and see if there is any distortion when there is no projection. Ian -- Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot___ Geoserver-users mailing list Please make sure you read the following two resources before posting to this list: - Earning your support instead of buying it, but Ian Turton: http://www.ianturton.com/talks/foss4g.html#/ - The GeoServer user list posting guidelines: http://geoserver.org/comm/userlist-guidelines.html Geoserver-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/geoserver-users
[Geoserver-users] ENC: Buffer error
De: Alexandre Barboza Enviado: segunda-feira, 23 de outubro de 2017 14:29 Para: Ian Turton Assunto: RE: [Geoserver-users] Buffer error Hi Ian! Thanks again for the quick reply! We think about its answer. When we publish the Layer using EPSG 4326, the buffer results are being distorted when we measure it, our data is between latitudes -22 and -23. Does QGIS use some algorithm to compensate this distortion? This data distortion does not occur in the QGIS or other Gis software. Are any way to apply the same algorithm, if exist, used on QGIS on geoserver? best regards! De: Ian Turton <ijtur...@gmail.com> Enviado: segunda-feira, 23 de outubro de 2017 13:47 Para: Alexandre Barboza Cc: geoserver-users@lists.sourceforge.net Assunto: Re: [Geoserver-users] Buffer error Then your map is distorted, Google maps uses EPSG:3587 (or epsg:900913 if you are using old terms) and that is a web Mercator projection which has an increasing E-W distortion as you move away from the equator. The other possible issue is that depending on how you projected your point into a local CRS and then projected the buffer back to WGS there is a chance to introduce inaccuracies into the process. Unless you just guessed a degrees to metres conversion factor that seemed about right for one of your points? Anyway, on that map circular buffers should look stretched out like yours do. Ian On 23 October 2017 at 16:26, Alexandre Barboza <ambarb...@hotmail.com<mailto:ambarb...@hotmail.com>> wrote: Hi Ian Thanks for your answer! We are using EPSG 4326 projection, and display it on Google Maps API, always tiled. When we open it on QGIS the buffer size dos not is the same that we specified on X axis and Y axis. sample: when we do a buffer of 500 meters (radius) the x axis result about 450 meters and Y axis have 500 meters. On this url http://www.ide.emplasa.sp.gov.br/geoserver/emplasa/TESTE_BUFFER_GEOWGS84/wms? we did a buffer with distance of 500 meters using EPSG 4326 layer On our website the buffer url is http://www.ide.emplasa.sp.gov.br/geoserver/emplasa/LOCALIDADES_EMPLASA_SAUDE/wms?styles=SYS_SIMM_ESTILO_BUFFER_DINAMICO_THE_GEOM=polygonStrokecolor:003300;polygonFillcolor:FF;bufferSize:500_FILTER=NOME_MUNIC%20LIKE%20%27Diadema%27=WMS=1.1.1=GetMap=emplasa:LOCALIDADES_EMPLASA_SAUDE=image/png=false=true=EPSG:900913=-5190379.968676608,-2727273.1692150906,-5187933.9837714825,-2724827.184309963=256=256 De: Ian Turton <ijtur...@gmail.com<mailto:ijtur...@gmail.com>> Enviado: segunda-feira, 23 de outubro de 2017 12:49 Para: Alexandre Barboza Cc: geoserver-users@lists.sourceforge.net<mailto:geoserver-users@lists.sourceforge.net> Assunto: Re: [Geoserver-users] Buffer error TBH that looks like a projected (EPSG:3857) map to me, so I would expect some distortion. You probably don't want to use tiles for that layer either, or maybe experiment with gutters to see if that helps with the edge cases. Please show the actual request to the buffer process so we can test it and see if there is any distortion when there is no projection. Ian -- Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot___ Geoserver-users mailing list Please make sure you read the following two resources before posting to this list: - Earning your support instead of buying it, but Ian Turton: http://www.ianturton.com/talks/foss4g.html#/ - The GeoServer user list posting guidelines: http://geoserver.org/comm/userlist-guidelines.html Geoserver-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/geoserver-users
