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Message: 4
Date: Sun, 9 Nov 2008 21:56:31 +1100
From: "Matt B" <mattslists@gmail.com>
Subject: [GRASS-user] Help with Georeferencing
To: grass-user@lists.osgeo.org
Message-ID:
<4ae765870811090256g5298d380o81b9e5a3872f204a@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"Hi Group,
I'm slowly figuring out how to use grass but encountering the odd problem.
Actually, I haven't managed to get much done with grass at all yet but I'm
writing that off to the learning curve.
At the moment I'm trying to georectify a stitched together google earth
image (I'm aware of the various legal issues that go with this and I'm just
using a few images to see if the work I want to do is feasible with this
type of data, if it is I'll look at purchasing data).I've imported the raster into grass using gdal, it splits it up into 3 (RGB)
files? and I can display it (in the wrong place at the wrong scale). I also
have the coordinates of the 4 corner points of the image and those are what
I'm using to georeference using the georeferencing tool from the file menu.I keep getting this error when I hit the "georectify" button in the
georeferencing tool:Traceback (most recent call last):
File "/usr/lib/grass/etc/wxpython/gui_modules/georect.py", line 825, in
OnGeorect
self.SaveGCPs()
TypeError: SaveGCPs() takes exactly 2 arguments (1 given)
Traceback (most recent call last):
File "/usr/lib/grass/etc/wxpython/gui_modules/georect.py", line 825, in
OnGeorect
self.SaveGCPs()
TypeError: SaveGCPs() takes exactly 2 arguments (1 given)(python:11374): Gdk-CRITICAL **: gdk_window_set_geometry_hints: assertion
`GDK_IS_WINDOW (window)' failedGRASS_INFO_MESSAGE(12418,1): Group <morondavaGE> has no target
GRASS_INFO_END(12418,1)It also took me a while to figure out how to set up image groups. I'm still
not sure if I've got that correct but that doesn't look like what the
problem is.
I am able to get the image aligned in qgis but stage 2 of my work will
involve some simple image classification (no doubt the subject of the next
few emails to this list). I'd also like to be able to know enough about how
grass works to be able to use it properly so I'm persevering with grass for
the time being.Thanks
Matt
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Matt,
I realise that Hamish and others have already offered some input here,
but here's another 2c worth.
Although there's a "single click" interface for georeferencing, I still
find it works better if I follow the step-by-step process.
- i.group at the command line, to create a map group
- i.target at the command line, to point your group "towards" the place
where you want the georeferenced image to end up
- d.mon start=x0 to get an x-monitor up and running
- i.points <group> to start working.
Second thought. If you're not seeking super-high quality, use
r.composite to combine your three images into one.
Richard Chirgwin