[Qgis-user] Wrong area count QGIS 3.20+?

[Sebastian Gutwein]

Yes that was my read as well except previously it was the Grass method and
now it is Geographic Lib method because that is theoretically more accurate
and is the same method that is used in Postgis and other places. The
switched happened because someone noticed the difference between QGIS’s
calculations and Postgis’s calculations. If I am reading the pull requests
correctly even Grass has switched to the Geographic Lib method. I’m
surprised that ArcGIS Pro uses the same method as the Grass method.

On Mon, Jan 3, 2022 at 2:57 AM Sadowski Jarosław <jaroslaw.sadowski at cpk.pl>
wrote:

> Sebastian,
>
>
>
> thank you very much for your precise answer and materials sent - I have
> read them carefully.
>
>
>
> So, as far as I can understand, QGIS has moved in version 3.20 to a new
> way of counting areas (other libraries? GRASS algorithm instead of
> Geographic lib? I have actually noticed a different nomenclature and
> definition of EPSG 2180 for some time in new versions…), that will be more
> accurate?
>
>
>
> I must admit that, for me as a GIS operator, it is surprising and sounds
> like bad news - so far surfaces have always been the same in various GIS
> software, whether or not it was open-source or commercial (ArcGIS Pro). So
> from this moment it will be that I will get different surfaces depending on
> the software it was calculated? :(
>
> with kind regards
> JS
>
> *_____________________________*
>
> *Jarosław Sadowski*
> Ekspert ds. Baz Danych i Analiz Przestrzennych | *Biuro Strategii i
> Planowania, Projektowania i Inżynierii Podprogramu Kolejowego*
> *Database and Spatial Analysis Expert |Railway Subprogramme Strategy &
> Planning, Design & Engineering Department*
> e: jaroslaw.sadowski at cpk.pl
>
> *From:* Sebastian Gutwein <bas at rdgland.com>
> *Sent:* Saturday, January 1, 2022 7:13 AM
> *To:* Sadowski Jarosław <jaroslaw.sadowski at cpk.pl>
> *Cc:* qgis-user at lists.osgeo.org
> *Subject:* Re: [Qgis-user] Wrong area count QGIS 3.20+?
>
>
>
> Nie otrzymujesz często wiadomości e-mail z adresu bas at rdgland.com. Dowiedz
> się, dlaczego jest to ważne <http://aka.ms/LearnAboutSenderIdentification>
>
> There was some discussion on this in the list serve back in January
> <https://eur06.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.osgeo.org%2Fpipermail%2Fqgis-user%2F2021-January%2F047638.html&data=04%7C01%7Cjaroslaw.sadowski%40cpk.pl%7Cf7cc24b07b7c42e8902a08d9ccedca61%7Cfa798250ca0b4a1bb47381cff4a1752b%7C1%7C0%7C637766145287655707%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=bUHOuswrG6tPdkebzFYem%2BVsSrgjFhbSLVcKCiu6TW0%3D&reserved=0>
> that resulted in this feature request
> <https://eur06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fqgis%2FQGIS%2Fissues%2F40888&data=04%7C01%7Cjaroslaw.sadowski%40cpk.pl%7Cf7cc24b07b7c42e8902a08d9ccedca61%7Cfa798250ca0b4a1bb47381cff4a1752b%7C1%7C0%7C637766145287655707%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=dY89NsDscjybmwQPMV9PjPOwckPlcv%2B8TEWjl69rTtM%3D&reserved=0>
> and this pull request
> <https://eur06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fqgis%2FQGIS%2Fpull%2F41726&data=04%7C01%7Cjaroslaw.sadowski%40cpk.pl%7Cf7cc24b07b7c42e8902a08d9ccedca61%7Cfa798250ca0b4a1bb47381cff4a1752b%7C1%7C0%7C637766145287655707%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=IRMFsaJYT7xpylDJCZNvXAUNzdmtTjNbI4VyQMKtedE%3D&reserved=0>.
> I tested your polygon, to the best of my limited ability, and the areas
> were indeed different in QGIS 3.16 and 3.22 as would be expected from that
> change . However it would be hoped that the area measurement would be more
> accurate in 3.22.
>
>
>
>
>
> On Fri, Dec 31, 2021 at 6:49 AM Sadowski Jarosław <
> jaroslaw.sadowski at cpk.pl> wrote:
>
> Dear all,
>
>
>
> I am asking for help with QGIS error/bug or verification of proper usage
> of basic QGIS functionality “$area”.
>
> From version 3.20 upwards, it counts areas differently than before (3.18
> calculated area is different than 3.20). Up to version 3.18 everything was
> fine, equal to calculations from ArcGIS Pro (geodesic mode).
>
> Anyone have an idea where the differences come from?
> This is example vector [image: Ikona zip] PL_2180.zip
> <https://eur06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcpkonline-my.sharepoint.com%2F%3Au%3A%2Fg%2Fpersonal%2Fjaroslaw_sadowski_cpk_pl%2FEVs0-TiEvPdBjMaqXrEvGfoBI0VussbJaYHdDVFfQnEYug%3Fe%3DVDY3rf-&data=04%7C01%7Cjaroslaw.sadowski%40cpk.pl%7Cf7cc24b07b7c42e8902a08d9ccedca61%7Cfa798250ca0b4a1bb47381cff4a1752b%7C1%7C0%7C637766145287655707%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=JlPtyjeeYHQxV0DdlGrsPwjTNy9FHqqyEqEpLNrian8%3D&reserved=0>:
> Polish borders in EPSG: 2180, in the table of attributes you can see the
> areas (hectares) calculated for different versions of the software.
>
>
>
> with wishes for more success in the new year
>
> Jarosław Sadowski
>
>
>
> *_________________________________*
>
> *Jarosław Sadowski*
> Ekspert ds. Baz Danych i Analiz Przestrzennych | *Biuro Strategii i
> Planowania, Projektowania i Inżynierii Podprogramu Kolejowego*
> *Database and Spatial Analysis Expert | Railway Subprogramme Strategy &
> Planning, Design & Engineering Department*
> e: jaroslaw.sadowski at cpk.pl
> m: +48 532 720 230
>
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Sent from a phone. Amazing! But possibly garbled. Sebastian Gutwein
Regenerative Design Group 1 Chevalier Ave Greenfield MA Bas at rdgland.com
(631) 241-1018
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