Re: [Qgis-user] AREA DE MAIOR INTERSEÇÃO

[Bruno Feliciano via QGIS-User]

Isso, teria que ser dinâmico.


Em sáb., 27 de abr. de 2024 às 04:48, Alexandre Neto 
escreveu:

> Sim, eu percebi o objectivo. Diria que q tua expressão devia funcionar,
> mas só experimentando. Não podes antes usar ferramentas de geoprocessamento
> para fazer isso? Ou tem mesmo de ser dinâmico? É que com a quantidade de
> intersecções, se as camadas tiverem muitos poligonos a coisa pode ficar
> muito lenta.
>
> Sent with Shortwave
> 
>
> On Sat Apr 27, 2024, 03:07 AM GMT, Bruno Feliciano
>  wrote:
>
> Vou explicar o que eu quero
>
> Digamos que você tenha uma camada chamada "IMÓVEIS_RURAL" e outra chamada
> "LIMITE_MUNICIPAL". Na camada "LIMITE_MUNICIPAL", há duas áreas em que um
> imovel(lote) se sobrepõem: uma área de 10.395,32 m² e outra de 19.604,69
> m². Você deseja calcular a área de sobreposição e identificar a maior área
> de sobreposição, que é de 19.604,69 m². Em seguida, você quer usar o valor
> da coluna "município" na camada "LIMITE_MUNICIPAL" correspondente a essa
> maior área de sobreposição e preencher o valor desejado!
>
> Espero que essa seja uma boa forma de explica onde eu quero chegar.
>
>
>
>
> Em sex., 26 de abr. de 2024 às 19:01, Alexandre Neto <
> senhor.n...@gmail.com> escreveu:
>
>> Ah sim, essa expressão faz sentido. Que resultados devolve?
>>
>> A sexta, 26/04/2024, 21:00, Bruno Feliciano <
>> brunofelicianodelima...@gmail.com> escreveu:
>>
>>> Tentei e não funcionou.
>>> Acabei optando por outra expressão e também não funcionou.
>>>
>>> Essa no caso, não retornou o resultado que eu esperava.
>>>
>>> aggregate(
>>> layer:= 'LIMITE_MUNICIPAL',
>>> aggregate:='max',
>>> expression:=municipio,
>>> filter:=intersects($geometry, geometry(@parent)),
>>> order_by:=area(intersection($geometry, geometry(@parent)))
>>> )
>>>
>>> Em sex., 26 de abr. de 2024 às 11:34, Alexandre Neto <
>>> senhor.n...@gmail.com> escreveu:
>>>
 Boa tarde,

 Com esta expressão ele está a obter um array com todos os valores e não
 apenas o primeiro.
 Em vez de "array_agg", talvez tenha de usar o minimun ou maxumum, mas
 colocando na opção order by a coluna ou o cálculo da área.

 Cumprimentos,

 Alexandre Neto


 On Tue, 23 Apr 2024 at 21:40, Bruno Feliciano via QGIS-User <
 qgis-user@lists.osgeo.org> wrote:

> Olá, estou usando essa expressão para puxar de uma camada um
> determinado valor, em casos onde minha poligonal intersecta com duas com
> duas, ele está trazendo o valor aleatório (ou o primeiro).
>
> Estou buscando uma expressão para puxar apenas o valor onde minha área
> faz maior intersecção.
>
> [image: image.png]
>
>
>
>
>
>
>
>
>
>
> ___
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Re: [Qgis-user] AREA DE MAIOR INTERSEÇÃO

[Alexandre Neto via QGIS-User]

Sim, eu percebi o objectivo. Diria que q tua expressão devia funcionar, mas só 
experimentando. Não podes antes usar ferramentas de geoprocessamento para fazer 
isso? Ou tem mesmo de ser dinâmico? É que com a quantidade de intersecções, se 
as camadas tiverem muitos poligonos a coisa pode ficar muito lenta.

Sent with Shortwave 


On Sat Apr 27, 2024, 03:07 AM GMT, Bruno Feliciano 
 wrote:
> Vou explicar o que eu quero
>
> Digamos que você tenha uma camada chamada "IMÓVEIS_RURAL" e outra chamada 
> "LIMITE_MUNICIPAL". Na camada "LIMITE_MUNICIPAL", há duas áreas em que um 
> imovel(lote) se sobrepõem: uma área de 10.395,32 m² e outra de 19.604,69 m². 
> Você deseja calcular a área de sobreposição e identificar a maior área de 
> sobreposição, que é de 19.604,69 m². Em seguida, você quer usar o valor da 
> coluna "município" na camada "LIMITE_MUNICIPAL" correspondente a essa maior 
> área de sobreposição e preencher o valor desejado!
>
> Espero que essa seja uma boa forma de explica onde eu quero chegar.
>
>
>
>
> Em sex., 26 de abr. de 2024 às 19:01, Alexandre Neto  > escreveu:
>> Ah sim, essa expressão faz sentido. Que resultados devolve?
>>
>> A sexta, 26/04/2024, 21:00, Bruno Feliciano 
>> > > escreveu:
>>> Tentei e não funcionou.
>>> Acabei optando por outra expressão e também não funcionou.
>>>
>>> Essa no caso, não retornou o resultado que eu esperava.
>>>
>>> aggregate(
>>> layer:= 'LIMITE_MUNICIPAL',
>>> aggregate:='max',
>>> expression:=municipio,
>>> filter:=intersects($geometry, geometry(@parent)),
>>> order_by:=area(intersection($geometry, geometry(@parent)))
>>> )
>>>
>>> Em sex., 26 de abr. de 2024 às 11:34, Alexandre Neto >> > escreveu:
 Boa tarde,

 Com esta expressão ele está a obter um array com todos os valores e não 
 apenas o primeiro.
 Em vez de "array_agg", talvez tenha de usar o minimun ou maxumum, mas 
 colocando na opção order by a coluna ou o cálculo da área.

 Cumprimentos,

 Alexandre Neto


 On Tue, 23 Apr 2024 at 21:40, Bruno Feliciano via QGIS-User 
 mailto:qgis-user@lists.osgeo.org>> wrote:
> Olá, estou usando essa expressão para puxar de uma camada um determinado 
> valor, em casos onde minha poligonal intersecta com duas com duas, ele 
> está trazendo o valor aleatório (ou o primeiro).
>
> Estou buscando uma expressão para puxar apenas o valor onde minha área 
> faz maior intersecção.
>
[image]
>
>
>
>
>
>
>
>
>
>
> ___
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> QGIS-User@lists.osgeo.org 
> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user 
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Re: [Qgis-user] AREA DE MAIOR INTERSEÇÃO

[Bruno Feliciano via QGIS-User]

Vou explicar o que eu quero

Digamos que você tenha uma camada chamada "IMÓVEIS_RURAL" e outra chamada
"LIMITE_MUNICIPAL". Na camada "LIMITE_MUNICIPAL", há duas áreas em que um
imovel(lote) se sobrepõem: uma área de 10.395,32 m² e outra de 19.604,69
m². Você deseja calcular a área de sobreposição e identificar a maior área
de sobreposição, que é de 19.604,69 m². Em seguida, você quer usar o valor
da coluna "município" na camada "LIMITE_MUNICIPAL" correspondente a essa
maior área de sobreposição e preencher o valor desejado!

Espero que essa seja uma boa forma de explica onde eu quero chegar.




Em sex., 26 de abr. de 2024 às 19:01, Alexandre Neto 
escreveu:

> Ah sim, essa expressão faz sentido. Que resultados devolve?
>
> A sexta, 26/04/2024, 21:00, Bruno Feliciano <
> brunofelicianodelima...@gmail.com> escreveu:
>
>> Tentei e não funcionou.
>> Acabei optando por outra expressão e também não funcionou.
>>
>> Essa no caso, não retornou o resultado que eu esperava.
>>
>> aggregate(
>> layer:= 'LIMITE_MUNICIPAL',
>> aggregate:='max',
>> expression:=municipio,
>> filter:=intersects($geometry, geometry(@parent)),
>> order_by:=area(intersection($geometry, geometry(@parent)))
>> )
>>
>> Em sex., 26 de abr. de 2024 às 11:34, Alexandre Neto <
>> senhor.n...@gmail.com> escreveu:
>>
>>> Boa tarde,
>>>
>>> Com esta expressão ele está a obter um array com todos os valores e não
>>> apenas o primeiro.
>>> Em vez de "array_agg", talvez tenha de usar o minimun ou maxumum, mas
>>> colocando na opção order by a coluna ou o cálculo da área.
>>>
>>> Cumprimentos,
>>>
>>> Alexandre Neto
>>>
>>>
>>> On Tue, 23 Apr 2024 at 21:40, Bruno Feliciano via QGIS-User <
>>> qgis-user@lists.osgeo.org> wrote:
>>>
 Olá, estou usando essa expressão para puxar de uma camada um
 determinado valor, em casos onde minha poligonal intersecta com duas com
 duas, ele está trazendo o valor aleatório (ou o primeiro).

 Estou buscando uma expressão para puxar apenas o valor onde minha área
 faz maior intersecção.

 [image: image.png]










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Re: [Qgis-user] AREA DE MAIOR INTERSEÇÃO

[Alexandre Neto via QGIS-User]

Ah sim, essa expressão faz sentido. Que resultados devolve?

A sexta, 26/04/2024, 21:00, Bruno Feliciano <
brunofelicianodelima...@gmail.com> escreveu:

> Tentei e não funcionou.
> Acabei optando por outra expressão e também não funcionou.
>
> Essa no caso, não retornou o resultado que eu esperava.
>
> aggregate(
> layer:= 'LIMITE_MUNICIPAL',
> aggregate:='max',
> expression:=municipio,
> filter:=intersects($geometry, geometry(@parent)),
> order_by:=area(intersection($geometry, geometry(@parent)))
> )
>
> Em sex., 26 de abr. de 2024 às 11:34, Alexandre Neto <
> senhor.n...@gmail.com> escreveu:
>
>> Boa tarde,
>>
>> Com esta expressão ele está a obter um array com todos os valores e não
>> apenas o primeiro.
>> Em vez de "array_agg", talvez tenha de usar o minimun ou maxumum, mas
>> colocando na opção order by a coluna ou o cálculo da área.
>>
>> Cumprimentos,
>>
>> Alexandre Neto
>>
>>
>> On Tue, 23 Apr 2024 at 21:40, Bruno Feliciano via QGIS-User <
>> qgis-user@lists.osgeo.org> wrote:
>>
>>> Olá, estou usando essa expressão para puxar de uma camada um determinado
>>> valor, em casos onde minha poligonal intersecta com duas com duas, ele
>>> está trazendo o valor aleatório (ou o primeiro).
>>>
>>> Estou buscando uma expressão para puxar apenas o valor onde minha área
>>> faz maior intersecção.
>>>
>>> [image: image.png]
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> ___
>>> QGIS-User mailing list
>>> QGIS-User@lists.osgeo.org
>>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
>>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
>>>
>>
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Re: [Qgis-user] AREA DE MAIOR INTERSEÇÃO

[Bruno Feliciano via QGIS-User]

Tentei e não funcionou.
Acabei optando por outra expressão e também não funcionou.

Essa no caso, não retornou o resultado que eu esperava.

aggregate(
layer:= 'LIMITE_MUNICIPAL',
aggregate:='max',
expression:=municipio,
filter:=intersects($geometry, geometry(@parent)),
order_by:=area(intersection($geometry, geometry(@parent)))
)

Em sex., 26 de abr. de 2024 às 11:34, Alexandre Neto 
escreveu:

> Boa tarde,
>
> Com esta expressão ele está a obter um array com todos os valores e não
> apenas o primeiro.
> Em vez de "array_agg", talvez tenha de usar o minimun ou maxumum, mas
> colocando na opção order by a coluna ou o cálculo da área.
>
> Cumprimentos,
>
> Alexandre Neto
>
>
> On Tue, 23 Apr 2024 at 21:40, Bruno Feliciano via QGIS-User <
> qgis-user@lists.osgeo.org> wrote:
>
>> Olá, estou usando essa expressão para puxar de uma camada um determinado
>> valor, em casos onde minha poligonal intersecta com duas com duas, ele
>> está trazendo o valor aleatório (ou o primeiro).
>>
>> Estou buscando uma expressão para puxar apenas o valor onde minha área
>> faz maior intersecção.
>>
>> [image: image.png]
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> ___
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>> QGIS-User@lists.osgeo.org
>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
>>
>
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Re: [Qgis-user] AREA DE MAIOR INTERSEÇÃO

[Alexandre Neto via QGIS-User]

Boa tarde,

Com esta expressão ele está a obter um array com todos os valores e não
apenas o primeiro.
Em vez de "array_agg", talvez tenha de usar o minimun ou maxumum, mas
colocando na opção order by a coluna ou o cálculo da área.

Cumprimentos,

Alexandre Neto


On Tue, 23 Apr 2024 at 21:40, Bruno Feliciano via QGIS-User <
qgis-user@lists.osgeo.org> wrote:

> Olá, estou usando essa expressão para puxar de uma camada um determinado
> valor, em casos onde minha poligonal intersecta com duas com duas, ele
> está trazendo o valor aleatório (ou o primeiro).
>
> Estou buscando uma expressão para puxar apenas o valor onde minha área faz
> maior intersecção.
>
> [image: image.png]
>
>
>
>
>
>
>
>
>
>
> ___
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[Qgis-user] AREA DE MAIOR INTERSEÇÃO

[Bruno Feliciano via QGIS-User]

Olá, estou usando essa expressão para puxar de uma camada um determinado
valor, em casos onde minha poligonal intersecta com duas com duas, ele
está trazendo o valor aleatório (ou o primeiro).

Estou buscando uma expressão para puxar apenas o valor onde minha área faz
maior intersecção.

[image: image.png]
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Re: [Qgis-user] area

[labrinos]

Thank you Håvard.
That was very helpful.
It works.

Nikos


Παραθέτοντας από Håvard Tveite :


For "hover" (get on screen the area of a region when
the cursor is above it):

Open the region layer's properties, go to "Display",
insert [%  $area  %] in the HTML Map Tip text area,
and click "OK".  Move the cursor over a region, and
its area should be displayed by your cursor.

Håvard

On 15.03.2020 19:39, labri...@eled.auth.gr wrote:


Hi all,

How can I get on screen the area of a selected region?
Can I get on screen the area of a region when the cursor is above it?

thank you
Nikos






--
Δρ. Νίκος Λαμπρινός
Καθηγητής της Διδασκαλίας της Γεωγραφίας
Τμήμα Δημοτικής Εκπαίδευσης
Α.Π.Θ. 54124 Θεσσαλονίκη
Τηλ.: 2310 991201 / 991230
Email: labri...@eled.auth.gr
Web Page: http://users.auth.gr/labrinos/
  http://www.digital-earth.edu.gr/
  https://www.auth.gr/univUnits

-
Dr. Nikos Lambrinos
Professor of Geography Teaching
Director of the Sector of Science and New Technologies
President of the Hellenic digital earth Centre of Excellence
Faculty of Education
School of Primary Education
Dept. of Science and New Technologies
Aristotle University of Thessaloniki
GR-54124 Thessaloniki, Greece
Tel: +30 2310 991201
Email: labri...@eled.auth.gr
Web Page: http://users.auth.gr/labrinos/
  http://www.digital-earth.edu.gr/
  https://www.auth.gr/en/univUnits

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Re: [Qgis-user] area

[Håvard Tveite]

For "hover" (get on screen the area of a region when
the cursor is above it):

Open the region layer's properties, go to "Display",
insert [%  $area  %] in the HTML Map Tip text area,
and click "OK".  Move the cursor over a region, and
its area should be displayed by your cursor.

Håvard

On 15.03.2020 19:39, labri...@eled.auth.gr wrote:
> 
> Hi all,
> 
> How can I get on screen the area of a selected region?
> Can I get on screen the area of a region when the cursor is above it?
> 
> thank you
> Nikos
> 
> 
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Re: [Qgis-user] area

[shrawan tripathi]

Hi sir, as per my knowledge u can see the attributes from identifier tool
by putting on same.


On Mon, 16 Mar, 2020, 12:09 AM ,  wrote:

>
> Hi all,
>
> How can I get on screen the area of a selected region?
> Can I get on screen the area of a region when the cursor is above it?
>
> thank you
> Nikos
>
>
> --
> Δρ. Νίκος Λαμπρινός
> Καθηγητής της Διδασκαλίας της Γεωγραφίας
> Τμήμα Δημοτικής Εκπαίδευσης
> Α.Π.Θ. 54124 Θεσσαλονίκη
> Τηλ.: 2310 991201 / 991230
> Email: labri...@eled.auth.gr
> Web Page: http://users.auth.gr/labrinos/
>   http://www.digital-earth.edu.gr/
>   https://www.auth.gr/univUnits
>
> -
> Dr. Nikos Lambrinos
> Professor of Geography Teaching
> Director of the Sector of Science and New Technologies
> President of the Hellenic digital earth Centre of Excellence
> Faculty of Education
> School of Primary Education
> Dept. of Science and New Technologies
> Aristotle University of Thessaloniki
> GR-54124 Thessaloniki, Greece
> Tel: +30 2310 991201
> Email: labri...@eled.auth.gr
> Web Page: http://users.auth.gr/labrinos/
>   http://www.digital-earth.edu.gr/
>   https://www.auth.gr/en/univUnits
>
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[Qgis-user] area

[labrinos]

Hi all,

How can I get on screen the area of a selected region?
Can I get on screen the area of a region when the cursor is above it?

thank you
Nikos


--
Δρ. Νίκος Λαμπρινός
Καθηγητής της Διδασκαλίας της Γεωγραφίας
Τμήμα Δημοτικής Εκπαίδευσης
Α.Π.Θ. 54124 Θεσσαλονίκη
Τηλ.: 2310 991201 / 991230
Email: labri...@eled.auth.gr
Web Page: http://users.auth.gr/labrinos/
  http://www.digital-earth.edu.gr/
  https://www.auth.gr/univUnits

-
Dr. Nikos Lambrinos
Professor of Geography Teaching
Director of the Sector of Science and New Technologies
President of the Hellenic digital earth Centre of Excellence
Faculty of Education
School of Primary Education
Dept. of Science and New Technologies
Aristotle University of Thessaloniki
GR-54124 Thessaloniki, Greece
Tel: +30 2310 991201
Email: labri...@eled.auth.gr
Web Page: http://users.auth.gr/labrinos/
  http://www.digital-earth.edu.gr/
  https://www.auth.gr/en/univUnits

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Re: [Qgis-user] area units

[Mithoefer]

Dear Boaz,

you can adjust the settings for units in the project properties / 
general tab

Kind regards

Klaus Mithöfer

Geoinformatikbüro Dassau GmbH

Mit freundlichen Grüßen
Klaus Mithöfer



Geoinformatikbüro Dassau GmbH
Rethelstrasse 153
D - 40237 Düsseldorf
Tel: +49-1573-7514549
http://www.gbd-consult.de

Registergericht: Amtsgericht Düsseldorf, HR B 74022
Geschäftsführer: Otto Dassau

Am 01.10.2018 um 13:22 schrieb Boaz Bar Ilan:

hi
what is the way to show area units not on kilometer square and not as 
meter square but as meter square /1000 ?

thanks
boaz


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Re: [Qgis-user] area units

[Phil Wyatt]

Metres squared/10,000 equals hectares. You can calculate this via an expression 
and add it as a new attribute

Cheers - Phil, 


> On 1 Oct 2018, at 9:22 pm, Boaz Bar Ilan  wrote:
> 
> hi
> what is the way to show area units not on kilometer square and not as meter 
> square but as meter square /1000 ? 
> thanks
> boaz
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[Qgis-user] area units

[Boaz Bar Ilan]

hi
what is the way to show area units not on kilometer square and not as meter
square but as meter square /1000 ?
thanks
boaz
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Re: [Qgis-user] AREA ATTRIBUTE FOR VECTOR LAYER

[Christine]

Hi Ricardo,
if you want to get a density of school points in each polygon, you may
calculate this in the field calculator. 
Assure, you are working in a projected coordinate sytem. Open attribute
table and choose 'open field calculator'. With the field calculator dialog
open, give a name to a new attribute for school density, choose an
appropriate output field type (probably decimal number, real), output field
length and precision and use an expression pattern like 
   / $area 

You get the correct syntax of your   
doubleclicking on the field's name under 'fields and values'. Be aware that
$area will have the dimension of the squared coordinate reference system's
measure unit (feet or meters). If you want a density based e.g. on km you
have to devide your area accordingly. 

Regards, Christine






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Re: [Qgis-user] AREA ATTRIBUTE FOR VECTOR LAYER

[Renato Saboya]

Hello,
Open the layer attribute table, create a new (real) field (or select an
existing field)  and select the $area function under Geometry.
Cheers,
*Renato T. de Saboya*
Universidade Federal de Santa Catarina
Programa de Pós-Graduação em Arquitetura e Urbanismo (PósArq)
Urbanidades  | Infoarq
 | PósArq
 | Academia.edu
 | ResearchGate



On 17 August 2017 at 16:05, Ricardo Thompson  wrote:

> HI]i,
>
> I have a polygon vector layer and want to derive an area attribute to use
> to calculate the density of schools in each polygon. Can somebody help?
>
> Thanks,
>
> Ricardo
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Re: [Qgis-user] AREA ATTRIBUTE FOR VECTOR LAYER

[Christine]

Ricardo Thompson wrote
> I have a polygon vector layer and want to derive an area attribute to use
> to calculate the density of schools in each polygon. Can somebody help?

Hi Ricardo,
if you have a points layer (e.g. for school locations) and a polygon layer
you may count the number of points (schools) that are located in each
polygon with: 
Menu 'Vector' > analysis tools > Count points in polygon. Choosing this
opens a dialog where you can choose your input layers (polygon and points),
an attribute name for the points count and a name and path for the new file
that is created.

Regards, Christine




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[Qgis-user] AREA ATTRIBUTE FOR VECTOR LAYER

[Ricardo Thompson]

HI]i,

I have a polygon vector layer and want to derive an area attribute to use to 
calculate the density of schools in each polygon. Can somebody help?

Thanks,

Ricardo
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Re: [Qgis-user] Area Calculations - what the h... is going on?

[Tobias Wendorff]

Good work

-- 
Von einem iPhone gesendet und wird daher Fehler enthalten…

Am 10.07.2017 um 04:00 schrieb Nyall Dawson :

> On 7 July 2017 at 00:38, magerlin  wrote:
>> I normally use $area in the field calculator to calculate areas of polygon
>> but now this is really weird.
>> 
>> I have 5 polygons in the same shape file and tries to calculate the areas -
>> but two of the polygon get areas of about 100 times as big as they should be
>> while the 3 remaining polygons get ok areas. If I use area($geometry)
>> instead I get OK areas:
> 
> Thanks for reporting this - I've identified the issue and it's fixed
> now in master and the 2.18 branch (so fix will be in 2.18.11)
> 
> Nyall
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Re: [Qgis-user] Area Calculations - what the h... is going on?

[Nyall Dawson]

On 7 July 2017 at 00:38, magerlin  wrote:
> I normally use $area in the field calculator to calculate areas of polygon
> but now this is really weird.
>
> I have 5 polygons in the same shape file and tries to calculate the areas -
> but two of the polygon get areas of about 100 times as big as they should be
> while the 3 remaining polygons get ok areas. If I use area($geometry)
> instead I get OK areas:

Thanks for reporting this - I've identified the issue and it's fixed
now in master and the 2.18 branch (so fix will be in 2.18.11)

Nyall
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Re: [Qgis-user] Area Calculations - what the h... is going on?

[magerlin]

I normally use the latest version, right now 2.18.10 but I have also a
"stripped down" version with almost no plugins saved as "Qgis on a stick"
which I sometimes swap to if the current version (or the all to many plugins
I  cannot keep from installing) are making trouble. This is 2.18.1. (so it
is not calculated using 2.18.3 but 28.18.10, just me forgetting to update my
signature!).

Tested using version 2.18.1 instead of 2.18.10 and it calculates *apparently
correct areas using both $area and area($geometry)* (the 2 leftmost area
columns are version 2.18.10 and the 2 rightmost columns are 2.18.1):


 

So it appears to be *an error introduced between version 2.18.1 and version
2.18.10*.

It is a file I have originally received from someone else so I am not sure
about "Compoundcurve geometries". Copy/pasting from attribute table shows
the WKT as a mixture of Polygons and Multipolygons



-
Regards Morten

Currently using Qgis 2.18.10 (OSGeo4),
Windows 7, 64bit
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Re: [Qgis-user] Area Calculations - what the h... is going on?

[Neumann, Andreas]

Noticed that the issue in this thread was specific to geometries
containing CompoundCurve geometries. Not sure if you use them? 

Andreas 

On 2017-07-06 17:16, Neumann, Andreas wrote:

> Hi Morten, 
> 
> Sounds familiar - see 
> http://osgeo-org.1560.x6.nabble.com/Area-calculation-issues-td5305669.html 
> 
> Perhaps you have an older version of 2.18 without the bug fix? Note that 
> there is now version 2.8.10 with numerous bug fixes since 2.18.3 (which you 
> seem to use). 
> 
> Andreas 
> 
> On 2017-07-06 16:38, magerlin wrote:
> 
>> I normally use $area in the field calculator to calculate areas of polygon
>> but now this is really weird.
>> 
>> I have 5 polygons in the same shape file and tries to calculate the areas -
>> but two of the polygon get areas of about 100 times as big as they should be
>> while the 3 remaining polygons get ok areas. If I use area($geometry)
>> instead I get OK areas:
>> 
>>  
>> 
>> According to the field calculator:
>> $area: The area calculated by this function respects both the current
>> project's ellipsoid setting and area unit settings
>> 
>> Area($geometry):  Calculations are always planimetric in the Spatial
>> Reference System (SRS) of this geometry, and the units of the returned area
>> will match the units for the SRS.
>> 
>> According to the "Topology Checker" the topology of the polygons are OK.
>> 
>> The file is here (EPSG: 32634): 
>> Test_Area.zip
>>   
>> 
>> -
>> Regards Morten
>> 
>> Currently using Qgis 2.18.3 (OSGeo4),
>> Windows 7, 64bit
>> --
>> View this message in context: 
>> http://osgeo-org.1560.x6.nabble.com/Area-Calculations-what-the-h-is-going-on-tp5326908.html
>> Sent from the QGIS - User mailing list archive at Nabble.com.
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Re: [Qgis-user] Area Calculations - what the h... is going on?

[Neumann, Andreas]

Hi Morten, 

Sounds familiar - see
http://osgeo-org.1560.x6.nabble.com/Area-calculation-issues-td5305669.html


Perhaps you have an older version of 2.18 without the bug fix? Note that
there is now version 2.8.10 with numerous bug fixes since 2.18.3 (which
you seem to use). 

Andreas 

On 2017-07-06 16:38, magerlin wrote:

> I normally use $area in the field calculator to calculate areas of polygon
> but now this is really weird.
> 
> I have 5 polygons in the same shape file and tries to calculate the areas -
> but two of the polygon get areas of about 100 times as big as they should be
> while the 3 remaining polygons get ok areas. If I use area($geometry)
> instead I get OK areas:
> 
>  
> 
> According to the field calculator:
> $area: The area calculated by this function respects both the current
> project's ellipsoid setting and area unit settings
> 
> Area($geometry):  Calculations are always planimetric in the Spatial
> Reference System (SRS) of this geometry, and the units of the returned area
> will match the units for the SRS.
> 
> According to the "Topology Checker" the topology of the polygons are OK.
> 
> The file is here (EPSG: 32634): 
> Test_Area.zip
>   
> 
> -
> Regards Morten
> 
> Currently using Qgis 2.18.3 (OSGeo4),
> Windows 7, 64bit
> --
> View this message in context: 
> http://osgeo-org.1560.x6.nabble.com/Area-Calculations-what-the-h-is-going-on-tp5326908.html
> Sent from the QGIS - User mailing list archive at Nabble.com.
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[Qgis-user] Area Calculations - what the h... is going on?

[magerlin]

I normally use $area in the field calculator to calculate areas of polygon
but now this is really weird.

I have 5 polygons in the same shape file and tries to calculate the areas -
but two of the polygon get areas of about 100 times as big as they should be
while the 3 remaining polygons get ok areas. If I use area($geometry)
instead I get OK areas:

 

According to the field calculator:
$area: The area calculated by this function respects both the current
project's ellipsoid setting and area unit settings

Area($geometry):  Calculations are always planimetric in the Spatial
Reference System (SRS) of this geometry, and the units of the returned area
will match the units for the SRS.

According to the "Topology Checker" the topology of the polygons are OK.

The file is here (EPSG: 32634): 
Test_Area.zip
  



-
Regards Morten

Currently using Qgis 2.18.3 (OSGeo4),
Windows 7, 64bit
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Re: [Qgis-user] Area calculation tools

[ralfwessels]

Hi Stephane,
if you calculate areas (or length) with the "Add geometry Columns"-Tool, the
results depend on the settings you can make under "Calculate using". Here
you have the options Layer CRS, Project CRS or Ellipsoid.
Ellipsoid is calculating with the curvature of the earth (so far I know) and
the others depending on the CRS' of the layer or the project (when 'on the
fly' CRS transformation is enabled).
If you are using $area in the field calculator it depends if 'on the fly'
CRS transformation is enabled or not.
If it is not enabled it calculates with the layer CRS, if it is enabled it
should calculate with the project CRS.

These are my testing experiences so I'm not 100% sure, but maybe there is
someone who has more informations about this topic.
ralf





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[Qgis-user] Area calculation tools

[Stephane Goldstein]

Hello.
I've noticed that there are in the feature area calculated by Vector >
Geometry Tools > Export/Add Geometry Columns" vs. using $area in the field
calculator.

For the same polygon I got
151 482 883.964722 m2 for the first one and
152 548 334.467394 m2 for the second.
This is a 106ha difference for a 15k ha area.
Does someone know which one of the tools is more precise, and why ?

Thanks

Stephane
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Re: [Qgis-user] Area Calculation in Field Calculation

[Harish]

Yes I was a problem of version. I was using 1.8 on a system where 1.7.4 was
also installed and probably plugin did not update itself with installation
of 1.8. When I installed 1.8 on a machine which doesn't have any version of
QGIS, it showed correct window.

Thanks
Harish
On Sun, Jul 8, 2012 at 1:49 PM, Jeremy Hill  wrote:

>Harish,
>  As my screen capture shows, I am able to select the Layer or Project or
> Ellipsoid CRS. I am able to do it on a “Line” “Point” and “Polygon”
> Shapefile (.shp) file. I’m running QGIS 1.8 Lisboa. Maybe check and make
> sure that you have the most up-to-date version. Apart from that I’m not
> sure what else to tell you. Hopefully someone else can help.
>  Jeremy
>
>  *From:* Harish 
> *Sent:* Sunday, July 08, 2012 12:59 AM
> *To:* Jeremy Hill 
> *Cc:* qgis-user@lists.osgeo.org
> *Subject:* Re: [Qgis-user] Area Calculation in Field Calculation
>
> Thanks! point one is solved but for point two, export/add geometry tool
> returns the window as attached, there is no option for choosing CRS for
> area calculation.
>
> Regards
>
> On Fri, Jul 6, 2012 at 10:14 PM, Jeremy Hill  wrote:
>
>>
>>
>> --
>>
>> Message: 4
>> Date: Fri, 6 Jul 2012 15:16:09 +0530
>> From: Harish 
>> To: Qgis-user@lists.osgeo.org
>> Subject: [Qgis-user] Area calculation in field calculator
>> Message-ID:
>> 
>> >
>> Content-Type: text/plain; charset="iso-8859-1"
>>
>> 1-
>> I converted projection 4326 to 32643(UTM zone 43N) to get are calculation.
>> I used geometry operator as $area with creating a new field of decimal
>> (real) type with width 10 and 2 precision. I tried with different widths
>> and precisions, every time there are 7-8 digits after decimal, like,
>> 2361773.81506348
>> 2895003.41503906
>> 1384160.6237793
>> 10020411.4874268
>>
>> ANSWER1- You need to uncheck the "Toggle Editing" and "save" your
>> layer and then it will be displayed with the proper width and precision
>> that you set it to.
>>
>>
>> 2
>> Further I read in new functionality list of QGIS1.8 that area/length etc.
>> may be calculated by using project (if in metric units) CRS in QGIS 1.8,
>> without changing original CRS of layer if it is in Geographic coordinates.
>> Is this feature available in 1.8?
>>
>> ANSWER2---  It does give you the option that when you use "Export/Add
>> Geometry Column" that it gives you the option to Calculate using Layer CRS,
>> Project CRS, or Ellipsoid. You can save to a new layer or update the
>> current one which your using. I have not experimented with this in
>> different projections to verify the accurate data or the area/length but
>> the "plugin" does work.
>>
>> Regards
>>
>> OS-Windows7, QGIS 1.8 stand alone
>>
>
>



-- 
Harish Kumar Solanki, Assistant Professor
National Institute of Rural Development (NIRD),
Ministry of Rural Development, Government of India
Jaipur, Rajasthan, India- Pin-302006

Email- hksola...@nird.gov.in, harry.om2...@gmail.com,
Tele-Fax-0141-2209905, Mo.- 09214446732, 09414291732
Website-  http://www.nird.org.in,
http://watershed.rajasthan.gov.in/<http://www.nird.org.in>
LinkedIn: www.linkedIn.com/in/hksolanki
<http://www.nird.org.in>
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Re: [Qgis-user] Area Calculation in Field Calculation

[Jeremy Hill]

Harish,
As my screen capture shows, I am able to select the Layer or Project or 
Ellipsoid CRS. I am able to do it on a “Line” “Point” and “Polygon” Shapefile 
(.shp) file. I’m running QGIS 1.8 Lisboa. Maybe check and make sure that you 
have the most up-to-date version. Apart from that I’m not sure what else to 
tell you. Hopefully someone else can help.
Jeremy

From: Harish 
Sent: Sunday, July 08, 2012 12:59 AM
To: Jeremy Hill 
Cc: qgis-user@lists.osgeo.org 
Subject: Re: [Qgis-user] Area Calculation in Field Calculation

Thanks! point one is solved but for point two, export/add geometry tool returns 
the window as attached, there is no option for choosing CRS for area 
calculation.

Regards


On Fri, Jul 6, 2012 at 10:14 PM, Jeremy Hill  wrote:



  --

  Message: 4
  Date: Fri, 6 Jul 2012 15:16:09 +0530
  From: Harish 
  To: Qgis-user@lists.osgeo.org
  Subject: [Qgis-user] Area calculation in field calculator
  Message-ID:
  
  Content-Type: text/plain; charset="iso-8859-1"

  1-
  I converted projection 4326 to 32643(UTM zone 43N) to get are calculation.
  I used geometry operator as $area with creating a new field of decimal
  (real) type with width 10 and 2 precision. I tried with different widths
  and precisions, every time there are 7-8 digits after decimal, like,
  2361773.81506348
  2895003.41503906
  1384160.6237793
  10020411.4874268

  ANSWER1- You need to uncheck the "Toggle Editing" and "save" your layer 
and then it will be displayed with the proper width and precision that you set 
it to.


  2
  Further I read in new functionality list of QGIS1.8 that area/length etc.
  may be calculated by using project (if in metric units) CRS in QGIS 1.8,
  without changing original CRS of layer if it is in Geographic coordinates.
  Is this feature available in 1.8?

  ANSWER2---  It does give you the option that when you use "Export/Add 
Geometry Column" that it gives you the option to Calculate using Layer CRS, 
Project CRS, or Ellipsoid. You can save to a new layer or update the current 
one which your using. I have not experimented with this in different 
projections to verify the accurate data or the area/length but the "plugin" 
does work.

  Regards

  OS-Windows7, QGIS 1.8 stand alone

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Re: [Qgis-user] Area Calculation in Field Calculation

[Jeremy Hill]

--

Message: 4
Date: Fri, 6 Jul 2012 15:16:09 +0530
From: Harish 
To: Qgis-user@lists.osgeo.org
Subject: [Qgis-user] Area calculation in field calculator
Message-ID:

Content-Type: text/plain; charset="iso-8859-1"

1-
I converted projection 4326 to 32643(UTM zone 43N) to get are calculation.
I used geometry operator as $area with creating a new field of decimal
(real) type with width 10 and 2 precision. I tried with different widths
and precisions, every time there are 7-8 digits after decimal, like,
2361773.81506348
2895003.41503906
1384160.6237793
10020411.4874268

ANSWER1- You need to uncheck the "Toggle Editing" and "save" your layer 
and then it will be displayed with the proper width and precision that you 
set it to.



2
Further I read in new functionality list of QGIS1.8 that area/length etc.
may be calculated by using project (if in metric units) CRS in QGIS 1.8,
without changing original CRS of layer if it is in Geographic coordinates.
Is this feature available in 1.8?

ANSWER2---  It does give you the option that when you use "Export/Add 
Geometry Column" that it gives you the option to Calculate using Layer CRS, 
Project CRS, or Ellipsoid. You can save to a new layer or update the current 
one which your using. I have not experimented with this in different 
projections to verify the accurate data or the area/length but the "plugin" 
does work.


Regards

OS-Windows7, QGIS 1.8 stand alone

--
Harish Kumar Solanki, Assistant Professor
National Institute of Rural Development (NIRD),
Ministry of Rural Development, Government of India
Jaipur, Rajasthan, India- Pin-302006
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[Qgis-user] Area calculation in field calculator

[Harish]

1-
I converted projection 4326 to 32643(UTM zone 43N) to get are calculation.
I used geometry operator as $area with creating a new field of decimal
(real) type with width 10 and 2 precision. I tried with different widths
and precisions, every time there are 7-8 digits after decimal, like,
2361773.81506348
2895003.41503906
1384160.6237793
10020411.4874268

2
Further I read in new functionality list of QGIS1.8 that area/length etc.
may be calculated by using project (if in metric units) CRS in QGIS 1.8,
without changing original CRS of layer if it is in Geographic coordinates.
Is this feature available in 1.8?

Regards

OS-Windows7, QGIS 1.8 stand alone

-- 
Harish Kumar Solanki, Assistant Professor
National Institute of Rural Development (NIRD),
Ministry of Rural Development, Government of India
Jaipur, Rajasthan, India- Pin-302006
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Re: [Qgis-user] AREA and PERIMETER ...? how to use it ...?

[Giovanni Manghi]

> 
> if i want to add attribute field lenght and area to the table, how to
> process it step by step


two ways:

a) vector -> geometry tools -> add/export geometry columns

b) enter the vector properties then

attributes -> field calculator (you need to toggle editing and click the
calculator icon)



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[Qgis-user] AREA and PERIMETER ...? how to use it ...?

[herman palaquium]

hi all

why the plugin to measure lenght and area for polygon layer nothing  
worked ?


anybody help me to detail step by step how to make polygon layer that  
can be measure area and lenght ...?


if i want to add attribute field lenght and area to the table, how to  
process it step by step


thanks

from herman

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Re: [Qgis-user] Area Measuring Tool enhancements

[John C. Tull]

Hi Fred,

I think that is a good suggestion. I want to point out that one acre is 43,560 
sq.ft., not 43,500.

Cheers,
John

On Dec 19, 2009, at 4:58 PM, Fred LaPlante wrote:

> When the preferred measuring units are set to Feet, the area measuring tool 
> has a limitation for users with parcel sizes we have here in my town.  
> Currently areas of less than 0.01 square miles are shown in square feet and 
> above that switch to square miles with 2 decimal places shown.
> 
> I would like to recommend that area measurements stay in square feet until 
> reaching one acre (43,500sq. ft) and then show acres with one decimal place 
> until reaching 640 acres then switch to square miles with one decimal place.
> 
> Fred LaPlante
> 
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Re: [Qgis-user] Area Measuring Tool enhancements

[Fred LaPlante]

That would work for me.

The Settings|Options|MapTools screen currently allows you to choose 
between Feet or Meters. Unfortunately the english system of  square 
feet|acres|square miles isn't something that is easily converted in you 
head.


I suppose a pulldown would let you switch back and forth quickly perhaps 
so you could easily compare to some written records. But that would 
require more code work from developers than what I proposed.


Fred LaPlante

Andreas Neumann wrote:
it would even be nicer if the tool would offer a combobox with a unit 
choice. Because you may want to have the result in square meters, even 
if the result is a higher number.


Andreas

Fred LaPlante wrote:
When the preferred measuring units are set to Feet, the area 
measuring tool has a limitation for users with parcel sizes we have 
here in my town.  Currently areas of less than 0.01 square miles are 
shown in square feet and above that switch to square miles with 2 
decimal places shown.


I would like to recommend that area measurements stay in square feet 
until reaching one acre (43,500sq. ft) and then show acres with one 
decimal place until reaching 640 acres then switch to square miles 
with one decimal place.


Fred LaPlante

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Re: [Qgis-user] Area Measuring Tool enhancements

[Andreas Neumann]

it would even be nicer if the tool would offer a combobox with a unit 
choice. Because you may want to have the result in square meters, even 
if the result is a higher number.


Andreas

Fred LaPlante wrote:
When the preferred measuring units are set to Feet, the area measuring 
tool has a limitation for users with parcel sizes we have here in my 
town.  Currently areas of less than 0.01 square miles are shown in 
square feet and above that switch to square miles with 2 decimal 
places shown.


I would like to recommend that area measurements stay in square feet 
until reaching one acre (43,500sq. ft) and then show acres with one 
decimal place until reaching 640 acres then switch to square miles 
with one decimal place.


Fred LaPlante

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[Qgis-user] Area Measuring Tool enhancements

[Fred LaPlante]

When the preferred measuring units are set to Feet, the area measuring 
tool has a limitation for users with parcel sizes we have here in my 
town.  Currently areas of less than 0.01 square miles are shown in 
square feet and above that switch to square miles with 2 decimal places 
shown.


I would like to recommend that area measurements stay in square feet 
until reaching one acre (43,500sq. ft) and then show acres with one 
decimal place until reaching 640 acres then switch to square miles with 
one decimal place.


Fred LaPlante

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