[Qgis-user] Raster selection

[José María Michia]

2008/11/21 Agustin Lobo <aloboaleu at gmail.com>:
> Jose Maria,
>
> If your "layer in question is vector layer" why is the
> subject of your message "Raster selection"?

I think that the message with subject "Raster selection" is a message
from Sergio , not my. This message, I think, is product of the
interest of Sergio in my problem, and a product of a confusion about
the problem. I'm poor English writer, my apologies for imprecise on
describe them.

Subject of the original message, from my, is "select elements from a
wms layer". In this thread, Richard tell me, that the output from WMS,
is a flat image.

When I answered the message from Richard, I explained that I did not
know that, so, WMS is not what I need.

> I suggest:
>
> 1. Define a rectangle for your area of interest and save it
> as a vector layer. Use New Layer (be sure to define the layer as polygon),
> Toggle Editing on and Capture rectangle to define your rectangle. Toggle
> Editing off and save.
> 2. Use ftools/Geoprocessing tools/Clip
>
> It's clear that QGIS lacks 2 simple but critical tools on these issues:
>
> 1. A simpler way to define a rectangular polygon for a given area.
> Currently, it's hard to get a real rectangle by defining a polygon with 4
> points. Also, a tool just saving as a rectangle the currently displayed
> extent would be most practical (and perhaps also another defining a
> rectangle from the extent of a given object, which would be required to
> display the extent of geographical objects out of their metadata anyway).
>
> 2. Clipping raster layers.
>
> You mention that you use grass. Note that through the grass plugin you can
> also solve these problems with grass (although I don't like the fact that
> you have to go through the location definition and the import/export from/to
> grass; we should be able to solve these problems within qgis itself).
>
> If you have problems to communicate in English, you are welcome to write me
> in Spanish.
>
> Regards,
>
> Agus

Creo que estos consejos van a ser muy útiles para hacer alguna prueba más.

Habitualmente, cuando se trata de capas normales, comunes, no tengo
problemas con esta clase de tareas. Pero en este caso, la capa que
quiero procesar, además de ser una capa WFS, quiero obtenerla con la
generalización que MapServer realiza sobre los elementos de la capa, a
una escala determinada.

Mi objetivo final es reutilizar el sistema de etiquetado que realiza
MapServer con otros programas. QGIS lo hace muy bien, porque puedo
agregar capas de tipo WFS, y la visualiza con generalizada, tal como
la visualiza MapServer. Pero con GMT, no puedo leer esa capa WFS,
necesito capturar los datos de alguna manera. Hasta ahora, he
integrado los resultados al final del proceso de creación del mapa,
integrando archivos PS y PDF. Pero quería encontrar una mejor forma de
integrar esas etiquetas en GMT.

La forma óptima de realizar esta tarea, se muy bien que esta lejos de
mis intentos. Habría que aplicar un algoritmo de etiquetado sobre los
datos originales. Pero eso también parece mucho más dificil, por eso
quería buscar una forma rápida de utilizar las etiquetas que genera
MapServer.

Insisto: QGIS las muestra muy bien, pero quiero utilizarlas en otros programas.

Gracias a todos por su ayuda. (Thanks all for your help).

> ------------------------------
>
> Message: 8
> Date: Fri, 21 Nov 2008 01:30:16 -0300
> From: " Jos? Mar?a Michia " <jose.maria.michia at gmail.com>
> Subject: Re: [Qgis-user] Raster selection
> To: " Sergio Z?rate Pedroche " <szpedroche at yahoo.com.mx>
> Cc: Qgis-user at lists.osgeo.org
> Message-ID:
>        <a37ffbf90811202030t4d32fd3dwcefdb9e64df56247 at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> Thanks Sergio, but it's not what I'm looking to do. I'm difficult with
> english, and i can not explain precisely.
>
> The layer in question is vector layer, not raster. More exactly, is an
> LABEL/ANNOTATION layer. And to be more exact, I wish this layer
> processed by MapServer for generalize at certain scale.
>
> My previous post is about some alternatives that I've explored
> explored in QGIS. The raster extraction mentioned, is not useful for
> me in this case.
>
> 2008/11/21 Sergio Zárate Pedroche <szpedroche at yahoo.com.mx>:
>>
>> > Hi, José María,
>> > Have you tried MultiSpec?
>> > It allows for establishing a rectangle selection, either manually or by
>> > coordinates (rows, cols; degrees or meters) and then saving selection.
>> > I vave found it usefull for importing raster selections in QGis
>
> Yes, I tried MultiSpec. However, I am a Linux user, and I prefer to
> use gdal_translate and GRASS for handling raster files.
>
> Thank you very much Sergio
> José María
>
> --
> Dr. Agustin Lobo
> Institut de Ciencies de la Terra "Jaume Almera" (CSIC)
> LLuis Sole Sabaris s/n
> 08028 Barcelona
> Spain
> Tel. 34 934095410
> Fax. 34 934110012
> email: Agustin.Lobo at ija.csic.es
> http://www.ija.csic.es/gt/obster
>
>