Re: [Qgis-user] Getting landuse information for several circular polygons

[G. Allegri]

Hi Manuel,
I also suggest you to consider the analysis tools provided by Sextante [1].
It offers "bridges" to other GIS analysis software, like GRASS and SAGA,
and they have a lot of analysis functionalities and algorithms.
For example GRASS has the r.li.* [1 ]set of commamds for landscape analysis.

giovanni

[1] http://plugins.qgis.org/plugins/sextante/
[2] http://grass.fbk.eu/grass64/manuals/html64_user/r.li.html

2012/7/17 Manuel Spínola 

> Thank you very much Simon.
>
> No offense at all, by the contrary, very helpful and very grateful for
> your message.
>
> I will check all the stuff you suggested.
>
> I teach landscape ecology and wildlife habitat evaluation for master
> students, I use R for some topics, but I want use more QGIS and stay away
> from commercial software.  Our students (from all over Latin America)
> usually work under very restrictive budgets.
>
> Best,
>
> Manuel
>
>
> 2012/7/16 Simon Cropper 
>
>> Manuel,
>>
>> I am not aware of any specific tutorials for doing this work in QGIS.
>>
>> No offense but these tasks are relatively basic. Your comment "I found
>> this task kind of difficult to do in QGIS" is suggestive that you have
>> difficulty in either basic GIS concepts or extrapolating your existing
>> knowledge from a commercial package to QGIS.
>>
>> *Assuming you stick with QGIS*
>>
>> Micha Silver has provided a tutorial called "GIS basics with Quantum GIS"
>> http://www.osgeo.org/node/1058 that may help you master the basics.
>>
>> The QGIS website has a great section called "How do I do that in QGIS?"
>> that covers alot of material http://hub.qgis.org/projects/**
>> quantum-gis/wiki/How_do_I_do_**that_in_QGIS#How-do-I-do-that-**in-QGIS.
>> Note the large number of videos on youtube -- sometimes seeing it done can
>> help.
>>
>> *Assuming you are considering an alternative*
>>
>> The OSGeo Educational Content Inventory also has a wide variety of other
>> educational material available that might also help fill in the gaps.
>> http://www.osgeo.org/**educational_content
>>
>> Finally, QGIS is not the only fosGIS out there. Check out what is on
>> offer on the LiveDVD 
>> (http://wiki.osgeo.org/wiki/**Live_GIS_Disc
>> ).
>>
>> Personally, I found using gvSIG relatively easy when moving from ArcView.
>> Unfortunately the bulk of the tutorials are in Spanish; unlike QGIS which
>> are predominantly in English. See my website for details and a list of
>> ecological tutorials I have prepared to date.
>>
>> *Final Comment*
>>
>> All this material is predicated by the premise that you actually know
>> what things are called. Reprojection and transformation is a good example.
>> Projection, SRS and CRS another. When stuck, posing a problem on the forums
>> can help as others can help you with terminology and suggest methods to
>> solve you problems.
>>
>> I hope this helps.
>>
>>
>> On 17/07/12 11:50, Manuel Spínola wrote:
>>
>>> What I am trying to do is a very common task in landscape ecology.  The
>>> buffer could be considered a landscape for some species and some metrics
>>> could be obtained for these "landscapes", however, I found this task
>>> kind of difficult to do in QGIS.  Any input on this?  Is there any
>>> oriented landscape ecology tutorial for QGIS.
>>>
>>
>>
>> [snip]
>>
>>
>> --
>> Cheers Simon
>>
>>Simon Cropper - Open Content Creator
>>
>>Free and Open Source Software Workflow Guides
>>--**--
>>Introduction   
>> http://www.fossworkflowguides.**com
>>GIS Packages   
>> http://www.fossworkflowguides.**com/gis
>>bash / Python
>> http://www.fossworkflowguides.**com/scripting
>>
>>
>>
>
>
> --
> *Manuel Spínola, Ph.D.*
> Instituto Internacional en Conservación y Manejo de Vida Silvestre
> Universidad Nacional
> Apartado 1350-3000
> Heredia
> COSTA RICA
> mspin...@una.ac.cr
> mspinol...@gmail.com
> Teléfono: (506) 2277-3598
> Fax: (506) 2237-7036
> Personal website: Lobito de río
> Institutional website: ICOMVIS 
>
> ___
> Qgis-user mailing list
> Qgis-user@lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/qgis-user
>
>
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Re: [Qgis-user] Getting landuse information for several circular polygons

[Manuel Spínola]

Thank you very much Simon.

No offense at all, by the contrary, very helpful and very grateful for your
message.

I will check all the stuff you suggested.

I teach landscape ecology and wildlife habitat evaluation for master
students, I use R for some topics, but I want use more QGIS and stay away
from commercial software.  Our students (from all over Latin America)
usually work under very restrictive budgets.

Best,

Manuel

2012/7/16 Simon Cropper 

> Manuel,
>
> I am not aware of any specific tutorials for doing this work in QGIS.
>
> No offense but these tasks are relatively basic. Your comment "I found
> this task kind of difficult to do in QGIS" is suggestive that you have
> difficulty in either basic GIS concepts or extrapolating your existing
> knowledge from a commercial package to QGIS.
>
> *Assuming you stick with QGIS*
>
> Micha Silver has provided a tutorial called "GIS basics with Quantum GIS"
> http://www.osgeo.org/node/1058 that may help you master the basics.
>
> The QGIS website has a great section called "How do I do that in QGIS?"
> that covers alot of material http://hub.qgis.org/projects/**
> quantum-gis/wiki/How_do_I_do_**that_in_QGIS#How-do-I-do-that-**in-QGIS.
> Note the large number of videos on youtube -- sometimes seeing it done can
> help.
>
> *Assuming you are considering an alternative*
>
> The OSGeo Educational Content Inventory also has a wide variety of other
> educational material available that might also help fill in the gaps.
> http://www.osgeo.org/**educational_content
>
> Finally, QGIS is not the only fosGIS out there. Check out what is on offer
> on the LiveDVD 
> (http://wiki.osgeo.org/wiki/**Live_GIS_Disc
> ).
>
> Personally, I found using gvSIG relatively easy when moving from ArcView.
> Unfortunately the bulk of the tutorials are in Spanish; unlike QGIS which
> are predominantly in English. See my website for details and a list of
> ecological tutorials I have prepared to date.
>
> *Final Comment*
>
> All this material is predicated by the premise that you actually know what
> things are called. Reprojection and transformation is a good example.
> Projection, SRS and CRS another. When stuck, posing a problem on the forums
> can help as others can help you with terminology and suggest methods to
> solve you problems.
>
> I hope this helps.
>
>
> On 17/07/12 11:50, Manuel Spínola wrote:
>
>> What I am trying to do is a very common task in landscape ecology.  The
>> buffer could be considered a landscape for some species and some metrics
>> could be obtained for these "landscapes", however, I found this task
>> kind of difficult to do in QGIS.  Any input on this?  Is there any
>> oriented landscape ecology tutorial for QGIS.
>>
>
>
> [snip]
>
>
> --
> Cheers Simon
>
>Simon Cropper - Open Content Creator
>
>Free and Open Source Software Workflow Guides
>--**--
>Introduction   
> http://www.fossworkflowguides.**com
>GIS Packages   
> http://www.fossworkflowguides.**com/gis
>bash / Python
> http://www.fossworkflowguides.**com/scripting
>
>
>


-- 
*Manuel Spínola, Ph.D.*
Instituto Internacional en Conservación y Manejo de Vida Silvestre
Universidad Nacional
Apartado 1350-3000
Heredia
COSTA RICA
mspin...@una.ac.cr
mspinol...@gmail.com
Teléfono: (506) 2277-3598
Fax: (506) 2237-7036
Personal website: Lobito de río 
Institutional website: ICOMVIS 
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Re: [Qgis-user] Getting landuse information for several circular polygons

[Simon Cropper]

Manuel,

I am not aware of any specific tutorials for doing this work in QGIS.

No offense but these tasks are relatively basic. Your comment "I found 
this task kind of difficult to do in QGIS" is suggestive that you have 
difficulty in either basic GIS concepts or extrapolating your existing 
knowledge from a commercial package to QGIS.


*Assuming you stick with QGIS*

Micha Silver has provided a tutorial called "GIS basics with Quantum 
GIS" http://www.osgeo.org/node/1058 that may help you master the basics.


The QGIS website has a great section called "How do I do that in QGIS?" 
that covers alot of material 
http://hub.qgis.org/projects/quantum-gis/wiki/How_do_I_do_that_in_QGIS#How-do-I-do-that-in-QGIS. 
Note the large number of videos on youtube -- sometimes seeing it done 
can help.


*Assuming you are considering an alternative*

The OSGeo Educational Content Inventory also has a wide variety of other 
educational material available that might also help fill in the gaps. 
http://www.osgeo.org/educational_content


Finally, QGIS is not the only fosGIS out there. Check out what is on 
offer on the LiveDVD (http://wiki.osgeo.org/wiki/Live_GIS_Disc).


Personally, I found using gvSIG relatively easy when moving from 
ArcView. Unfortunately the bulk of the tutorials are in Spanish; unlike 
QGIS which are predominantly in English. See my website for details and 
a list of ecological tutorials I have prepared to date.


*Final Comment*

All this material is predicated by the premise that you actually know 
what things are called. Reprojection and transformation is a good 
example. Projection, SRS and CRS another. When stuck, posing a problem 
on the forums can help as others can help you with terminology and 
suggest methods to solve you problems.


I hope this helps.

On 17/07/12 11:50, Manuel Spínola wrote:

What I am trying to do is a very common task in landscape ecology.  The
buffer could be considered a landscape for some species and some metrics
could be obtained for these "landscapes", however, I found this task
kind of difficult to do in QGIS.  Any input on this?  Is there any
oriented landscape ecology tutorial for QGIS.



[snip]

--
Cheers Simon

   Simon Cropper - Open Content Creator

   Free and Open Source Software Workflow Guides
   
   Introduction   http://www.fossworkflowguides.com
   GIS Packages   http://www.fossworkflowguides.com/gis
   bash / Pythonhttp://www.fossworkflowguides.com/scripting


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Re: [Qgis-user] Getting landuse information for several circular polygons

[Manuel Spínola]

Thank you very much Simon.

That works, specially the second option.

What I am trying to do is a very common task in landscape ecology.  The
buffer could be considered a landscape for some species and some metrics
could be obtained for these "landscapes", however, I found this task kind
of difficult to do in QGIS.  Any input on this?  Is there any oriented
landscape ecology tutorial for QGIS.

Best,

Manuel

2012/7/16 Simon Cropper 

>
> Manuel,
>
> Once you clip the layers, break the multi-part components apart use the
> following menu sequence "Vector > Geometry Tools > Multiparts to Single
> Parts" -- then they can be summed. You will need to relate you bits back to
> your buffer layers however, to match which bit goes in which buffer.
>
> Alternatively, and easier in my mind, you could "Union" your layers. This
> creates an exploded layer where each bit has attributes of both parent
> layers. You can then delete those elements that do not have a buffer value.
> Two steps but less messy.
>
>
> On 17/07/12 03:22, Manuel Spínola wrote:
>
>> Dear list members,
>>
>> I have a landuse layer and another layer with 20 circular polygons
>> (buffers) and I want to obtain the amount of each landuse category
>> within each circular polygon.  I tried "clip" from Geoprocessing Tools
>> but I dont get the information individualized for each circular polygon.
>>   Is it possible to get the landuse within each circular polygon in one
>> step?
>>
>> Best,
>>
>> Manuel
>>
>> --
>> *Manuel Spínola, Ph.D.*
>>
>> Instituto Internacional en Conservación y Manejo de Vida Silvestre
>> Universidad Nacional
>> Apartado 1350-3000
>> Heredia
>> COSTA RICA
>> mspin...@una.ac.cr 
>> mspinol...@gmail.com 
>>
>> Teléfono: (506) 2277-3598
>> Fax: (506) 2237-7036
>> Personal website: Lobito de río
>> 
>> >
>> Institutional website: ICOMVIS 
>>
>>
>> __**_
>> Qgis-user mailing list
>> Qgis-user@lists.osgeo.org
>> http://lists.osgeo.org/**mailman/listinfo/qgis-user
>>
>>
>
> --
> Cheers Simon
>
>Simon Cropper - Open Content Creator
>
>Free and Open Source Software Workflow Guides
>--**--
>Introduction   
> http://www.fossworkflowguides.**com
>GIS Packages   
> http://www.fossworkflowguides.**com/gis
>bash / Python
> http://www.fossworkflowguides.**com/scripting
>
>
>
> __**_
> Qgis-user mailing list
> Qgis-user@lists.osgeo.org
> http://lists.osgeo.org/**mailman/listinfo/qgis-user
>



-- 
*Manuel Spínola, Ph.D.*
Instituto Internacional en Conservación y Manejo de Vida Silvestre
Universidad Nacional
Apartado 1350-3000
Heredia
COSTA RICA
mspin...@una.ac.cr
mspinol...@gmail.com
Teléfono: (506) 2277-3598
Fax: (506) 2237-7036
Personal website: Lobito de río 
Institutional website: ICOMVIS 
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Re: [Qgis-user] Getting landuse information for several circular polygons

[Simon Cropper]

Manuel,

Once you clip the layers, break the multi-part components apart use the 
following menu sequence "Vector > Geometry Tools > Multiparts to Single 
Parts" -- then they can be summed. You will need to relate you bits back 
to your buffer layers however, to match which bit goes in which buffer.


Alternatively, and easier in my mind, you could "Union" your layers. 
This creates an exploded layer where each bit has attributes of both 
parent layers. You can then delete those elements that do not have a 
buffer value. Two steps but less messy.


On 17/07/12 03:22, Manuel Spínola wrote:

Dear list members,

I have a landuse layer and another layer with 20 circular polygons
(buffers) and I want to obtain the amount of each landuse category
within each circular polygon.  I tried "clip" from Geoprocessing Tools
but I dont get the information individualized for each circular polygon.
  Is it possible to get the landuse within each circular polygon in one
step?

Best,

Manuel

--
*Manuel Spínola, Ph.D.*
Instituto Internacional en Conservación y Manejo de Vida Silvestre
Universidad Nacional
Apartado 1350-3000
Heredia
COSTA RICA
mspin...@una.ac.cr 
mspinol...@gmail.com 
Teléfono: (506) 2277-3598
Fax: (506) 2237-7036
Personal website: Lobito de río

Institutional website: ICOMVIS 


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--
Cheers Simon

   Simon Cropper - Open Content Creator

   Free and Open Source Software Workflow Guides
   
   Introduction   http://www.fossworkflowguides.com
   GIS Packages   http://www.fossworkflowguides.com/gis
   bash / Pythonhttp://www.fossworkflowguides.com/scripting


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Re: [Qgis-user] Getting landuse information for several circular polygons

[Manuel Spínola]

Thank you very much Micha.

Your suggestion is based on writing a code, right?  I am doing this for
teaching purposes, is it possible to do the same based on the menu of QGIS?

Best,

Manuel


2012/7/16 Micha Silver 

> On 16/07/2012 20:22, Manuel Spínola wrote:
>
>> Dear list members,
>>
>> I have a landuse layer and another layer with 20 circular polygons
>> (buffers) and I want to obtain the amount of each landuse category within
>> each circular polygon.  I tried "clip" from Geoprocessing Tools but I dont
>> get the information individualized for each circular polygon.  Is it
>> possible to get the landuse within each circular polygon in one step?
>>
>>
> Not exactly "one step" but...
> If you don't mind to drop the vectors into spatialite, then a query can
> update the buffers layer with area of each landuse category as follows:
> Suppose "buffers" has a label column, and there are landuse categories
> lu1, lu2, lu3,  then:
>
> SELECT b.label AS Buffer,
> ST_Area(ST_Intersection(b.**Geometry, l.Geometry)) AS LandUse1
> FROM buffers AS b, landuse AS l
> WHERE l.category='lu1' AND
> ST_Intersects(b.Geometry, l.Geometry)
> GROUP BY b.buff_id;
>
> If you add columns to the buffers table to hold total area for each
> landuse category::
> ALTER TABLE buffers ADD COLUMN lu1_area float;
> ALTER TABLE buffers ADD COLUMN lu2_area float;
> 
>
> then you'd update each column like so:
> UPDATE buffers SET lu1_area=(
> SELECT ST_Area(ST_Intersection(b.**Geometry, l.Geometry)) AS LandUse1
> FROM buffers AS b, landuse AS l
> WHERE l.category='lu1' AND
> ST_Intersects(b.Geometry, l.Geometry) AND
> b.label=buffers.label
> );
>
> HTH,
> Micha
>
>  Best,
>>
>> Manuel
>>
>> --
>> *Manuel Spínola, Ph.D.*
>>
>> Instituto Internacional en Conservación y Manejo de Vida Silvestre
>> Universidad Nacional
>> Apartado 1350-3000
>> Heredia
>> COSTA RICA
>> mspin...@una.ac.cr 
>> mspinol...@gmail.com 
>>
>> Teléfono: (506) 2277-3598
>> Fax: (506) 2237-7036
>> Personal website: Lobito de río > site/lobitoderio/ >
>> Institutional website: ICOMVIS 
>>
>> This mail was received via Mail-SeCure System.
>>
>>
>> __**_
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>> http://lists.osgeo.org/**mailman/listinfo/qgis-user
>>
>> This mail was received via Mail-SeCure System.
>>
>>
>>
>


-- 
*Manuel Spínola, Ph.D.*
Instituto Internacional en Conservación y Manejo de Vida Silvestre
Universidad Nacional
Apartado 1350-3000
Heredia
COSTA RICA
mspin...@una.ac.cr
mspinol...@gmail.com
Teléfono: (506) 2277-3598
Fax: (506) 2237-7036
Personal website: Lobito de río 
Institutional website: ICOMVIS 
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Re: [Qgis-user] Getting landuse information for several circular polygons

[Micha Silver]

On 16/07/2012 20:22, Manuel Spínola wrote:

Dear list members,

I have a landuse layer and another layer with 20 circular polygons 
(buffers) and I want to obtain the amount of each landuse category 
within each circular polygon.  I tried "clip" from Geoprocessing Tools 
but I dont get the information individualized for each circular 
polygon.  Is it possible to get the landuse within each circular 
polygon in one step?




Not exactly "one step" but...
If you don't mind to drop the vectors into spatialite, then a query can 
update the buffers layer with area of each landuse category as follows:
Suppose "buffers" has a label column, and there are landuse categories 
lu1, lu2, lu3,  then:


SELECT b.label AS Buffer,
ST_Area(ST_Intersection(b.Geometry, l.Geometry)) AS LandUse1
FROM buffers AS b, landuse AS l
WHERE l.category='lu1' AND
ST_Intersects(b.Geometry, l.Geometry)
GROUP BY b.buff_id;

If you add columns to the buffers table to hold total area for each 
landuse category::

ALTER TABLE buffers ADD COLUMN lu1_area float;
ALTER TABLE buffers ADD COLUMN lu2_area float;


then you'd update each column like so:
UPDATE buffers SET lu1_area=(
SELECT ST_Area(ST_Intersection(b.Geometry, l.Geometry)) AS LandUse1
FROM buffers AS b, landuse AS l
WHERE l.category='lu1' AND
ST_Intersects(b.Geometry, l.Geometry) AND
b.label=buffers.label
);

HTH,
Micha


Best,

Manuel

--
*Manuel Spínola, Ph.D.*
Instituto Internacional en Conservación y Manejo de Vida Silvestre
Universidad Nacional
Apartado 1350-3000
Heredia
COSTA RICA
mspin...@una.ac.cr 
mspinol...@gmail.com 
Teléfono: (506) 2277-3598
Fax: (506) 2237-7036
Personal website: Lobito de río 


Institutional website: ICOMVIS 

This mail was received via Mail-SeCure System.


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[Qgis-user] Getting landuse information for several circular polygons

[Manuel Spínola]

Dear list members,

I have a landuse layer and another layer with 20 circular polygons
(buffers) and I want to obtain the amount of each landuse category within
each circular polygon.  I tried "clip" from Geoprocessing Tools but I dont
get the information individualized for each circular polygon.  Is it
possible to get the landuse within each circular polygon in one step?

Best,

Manuel

-- 
*Manuel Spínola, Ph.D.*
Instituto Internacional en Conservación y Manejo de Vida Silvestre
Universidad Nacional
Apartado 1350-3000
Heredia
COSTA RICA
mspin...@una.ac.cr
mspinol...@gmail.com
Teléfono: (506) 2277-3598
Fax: (506) 2237-7036
Personal website: Lobito de río 
Institutional website: ICOMVIS 
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