[Qgis-user] Raster selection

[Agustin Lobo]

Jose Maria,

If your "layer in question is vector layer" why is the
subject of your message "Raster selection"?

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

------------------------------

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