Re: [QGIS-Developer] Is the measurement tool using proj library?
Hi, Am 19.07.19 um 23:47 schrieb Nyall Dawson: On Fri, 19 Jul 2019 at 23:15, Andreas Neumann wrote: Hi Nyall and others, I was wrong, there is no difference in behaviour between proj493 and proj520. Nor is there a difference between Linux and Windows. We, as a user, made the mistake of creating test data in a new empty layer at around (0,0) and my colleague in a totally different area in the coordinate system in an area that isn't valid for the EPSG:2056 projection. The EPSG:2056 projection only works reasonably well in the bound of approx. 2485000 1075000 2828500 1300 Glad I'm not the only one who has made this mistake!! ;-) I felt so embarrassed that it took me quite long to find out about my/our mistake. I wonder if it would make sense to issue a warning if a user creates data outside of the valid bounds of a projection? It would definitely make sense for stupid people like myself ... This sounds like a good idea to me. When would you propose that we raise the warning? Possibly on saving edits to a layer? Yes - on saving a layer it it would make sense to check against the valid boundaries of a projection (if we have this information available). Probably not during editing. I think it should not prevent saving, if someone wants to that, but a warning in the messagebar would be useful to have, or perhaps even with a yes/no question - do you really want to save? Do you know what you are doing? Thanks, Andreas ___ QGIS-Developer mailing list QGIS-Developer@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer
Re: [QGIS-Developer] Is the measurement tool using proj library?
On Fri, 19 Jul 2019 at 23:15, Andreas Neumann wrote: > For myself, I decided to never make fun again about other people not > understanding projections, given that I make such mistakes myself ... I had this moment of realisation too while reading through https://lists.osgeo.org/pipermail/proj/2019-July/008703.html and https://www.openstreetmap.org/user/StephaneP/diary/390290 (all those "spatial isn't special" proponents trying to do data science on raw x/y alone are about to have a ten ton weight dropped on their heads) Nyall > > I wonder if it would make sense to issue a warning if a user creates data > outside of the valid bounds of a projection? It would definitely make sense > for stupid people like myself ... > > Thanks and greetings, > > Andreas > > On 2019-07-19 01:18, Nyall Dawson wrote: > > On Fri, 19 Jul 2019 at 00:38, Andreas Neumann wrote: > > > Hi, > > We are having issues on the QGIS 3.4 release that the difference between and > ellipsoidical and planimetric distance (and area) is huge. Too huge. > > We have this issue on Windows 3.4.9, but on Linux (a bit newer commit) I > don't have the same huge difference, but rather a very reasonable one. > > I noticed that while the Windows version was built with proj 520 and the > Linux version with 493, so a bit older. > > But I don't know if the measurement tool in QGIS is using proj at all or not? > If yes, could it be that newer proj releases made things worse regarding > ellipsoidical measurements? > > > It's possible. The actual measurement calculation uses code ported > from GRASS (and not the proj implementation of these algorithms), but > proj IS used in transforming map/measure coordinates prior to > calculating the distance. Possibly something has changed there which > is impacting this. > > Could you please test: > > 1. Do you see the same distance values when measuring feature lengths? > I.e. setup a layer with a feature with the same line as you are > measuring, and check the identify tool derived attributes or $length > value for it. > > 2. Can you confirm that the project ellipsoid settings are identical > between the windows & linux builds? > > 3. Can you share an example I can test with? > > Nyall > > ___ QGIS-Developer mailing list QGIS-Developer@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer
Re: [QGIS-Developer] Is the measurement tool using proj library?
On Fri, 19 Jul 2019 at 23:15, Andreas Neumann wrote: > > Hi Nyall and others, > > I was wrong, there is no difference in behaviour between proj493 and proj520. > Nor is there a difference between Linux and Windows. > > We, as a user, made the mistake of creating test data in a new empty layer at > around (0,0) and my colleague in a totally different area in the coordinate > system in an area that isn't valid for the EPSG:2056 projection. The > EPSG:2056 projection only works reasonably well in the bound of approx. > 2485000 1075000 2828500 1300 Glad I'm not the only one who has made this mistake!! > I wonder if it would make sense to issue a warning if a user creates data > outside of the valid bounds of a projection? It would definitely make sense > for stupid people like myself ... This sounds like a good idea to me. When would you propose that we raise the warning? Possibly on saving edits to a layer? Nyall > > Thanks and greetings, > > Andreas > > On 2019-07-19 01:18, Nyall Dawson wrote: > > On Fri, 19 Jul 2019 at 00:38, Andreas Neumann wrote: > > > Hi, > > We are having issues on the QGIS 3.4 release that the difference between and > ellipsoidical and planimetric distance (and area) is huge. Too huge. > > We have this issue on Windows 3.4.9, but on Linux (a bit newer commit) I > don't have the same huge difference, but rather a very reasonable one. > > I noticed that while the Windows version was built with proj 520 and the > Linux version with 493, so a bit older. > > But I don't know if the measurement tool in QGIS is using proj at all or not? > If yes, could it be that newer proj releases made things worse regarding > ellipsoidical measurements? > > > It's possible. The actual measurement calculation uses code ported > from GRASS (and not the proj implementation of these algorithms), but > proj IS used in transforming map/measure coordinates prior to > calculating the distance. Possibly something has changed there which > is impacting this. > > Could you please test: > > 1. Do you see the same distance values when measuring feature lengths? > I.e. setup a layer with a feature with the same line as you are > measuring, and check the identify tool derived attributes or $length > value for it. > > 2. Can you confirm that the project ellipsoid settings are identical > between the windows & linux builds? > > 3. Can you share an example I can test with? > > Nyall > > ___ QGIS-Developer mailing list QGIS-Developer@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer
Re: [QGIS-Developer] Is the measurement tool using proj library?
Hi Nyall and others, I was wrong, there is no difference in behaviour between proj493 and proj520. Nor is there a difference between Linux and Windows. We, as a user, made the mistake of creating test data in a new empty layer at around (0,0) and my colleague in a totally different area in the coordinate system in an area that isn't valid for the EPSG:2056 projection. The EPSG:2056 projection only works reasonably well in the bound of approx. 2485000 1075000 2828500 1300 It produces bogus results if the user creates data outside of this boundary, like at around 0,0. I was so embarrassed that it took me so long to find out our mistake. For the longest time I thought it was some bug in QGIS or proj, only to find out that both myself and my colleague created our test data outside of the valid bounds of the projection at totally different locations, but both outside of Switzerland. If we had some base layer below our test data rather than just creating empty project with no background maps, it wouldn't happen. When I moved the testdata into the valid bounds of the projection, the area difference between planimetric and ellipsoidic area was less than a square meter. For myself, I decided to never make fun again about other people not understanding projections, given that I make such mistakes myself ... I wonder if it would make sense to issue a warning if a user creates data outside of the valid bounds of a projection? It would definitely make sense for stupid people like myself ... Thanks and greetings, Andreas On 2019-07-19 01:18, Nyall Dawson wrote: On Fri, 19 Jul 2019 at 00:38, Andreas Neumann wrote: Hi, We are having issues on the QGIS 3.4 release that the difference between and ellipsoidical and planimetric distance (and area) is huge. Too huge. We have this issue on Windows 3.4.9, but on Linux (a bit newer commit) I don't have the same huge difference, but rather a very reasonable one. I noticed that while the Windows version was built with proj 520 and the Linux version with 493, so a bit older. But I don't know if the measurement tool in QGIS is using proj at all or not? If yes, could it be that newer proj releases made things worse regarding ellipsoidical measurements? It's possible. The actual measurement calculation uses code ported from GRASS (and not the proj implementation of these algorithms), but proj IS used in transforming map/measure coordinates prior to calculating the distance. Possibly something has changed there which is impacting this. Could you please test: 1. Do you see the same distance values when measuring feature lengths? I.e. setup a layer with a feature with the same line as you are measuring, and check the identify tool derived attributes or $length value for it. 2. Can you confirm that the project ellipsoid settings are identical between the windows & linux builds? 3. Can you share an example I can test with? Nyall<> <> ___ QGIS-Developer mailing list QGIS-Developer@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer
Re: [QGIS-Developer] Is the measurement tool using proj library?
On Fri, 19 Jul 2019 at 00:38, Andreas Neumann wrote: > > Hi, > > We are having issues on the QGIS 3.4 release that the difference between and > ellipsoidical and planimetric distance (and area) is huge. Too huge. > > We have this issue on Windows 3.4.9, but on Linux (a bit newer commit) I > don't have the same huge difference, but rather a very reasonable one. > > I noticed that while the Windows version was built with proj 520 and the > Linux version with 493, so a bit older. > > But I don't know if the measurement tool in QGIS is using proj at all or not? > If yes, could it be that newer proj releases made things worse regarding > ellipsoidical measurements? It's possible. The actual measurement calculation uses code ported from GRASS (and not the proj implementation of these algorithms), but proj IS used in transforming map/measure coordinates prior to calculating the distance. Possibly something has changed there which is impacting this. Could you please test: 1. Do you see the same distance values when measuring feature lengths? I.e. setup a layer with a feature with the same line as you are measuring, and check the identify tool derived attributes or $length value for it. 2. Can you confirm that the project ellipsoid settings are identical between the windows & linux builds? 3. Can you share an example I can test with? Nyall ___ QGIS-Developer mailing list QGIS-Developer@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer
Re: [QGIS-Developer] Is the measurement tool using proj library?
Andreas, How do your results compare with the "Shape Tools" measurement tool? It is based on the geographiclib library. Calvin On Thu, Jul 18, 2019 at 10:38 AM Andreas Neumann wrote: > Hi, > > We are having issues on the QGIS 3.4 release that the difference between > and ellipsoidical and planimetric distance (and area) is huge. Too huge. > > We have this issue on Windows 3.4.9, but on Linux (a bit newer commit) I > don't have the same huge difference, but rather a very reasonable one. > > I noticed that while the Windows version was built with proj 520 and the > Linux version with 493, so a bit older. > > But I don't know if the measurement tool in QGIS is using proj at all or > not? If yes, could it be that newer proj releases made things worse > regarding ellipsoidical measurements? > > Thanks, > Andreas > ___ > QGIS-Developer mailing list > QGIS-Developer@lists.osgeo.org > List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer ___ QGIS-Developer mailing list QGIS-Developer@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer
[QGIS-Developer] Is the measurement tool using proj library?
Hi, We are having issues on the QGIS 3.4 release that the difference between and ellipsoidical and planimetric distance (and area) is huge. Too huge. We have this issue on Windows 3.4.9, but on Linux (a bit newer commit) I don't have the same huge difference, but rather a very reasonable one. I noticed that while the Windows version was built with proj 520 and the Linux version with 493, so a bit older. But I don't know if the measurement tool in QGIS is using proj at all or not? If yes, could it be that newer proj releases made things worse regarding ellipsoidical measurements? Thanks, Andreas___ QGIS-Developer mailing list QGIS-Developer@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer
