[Qgis-user] Re: vector affine transformation

[Agustin Lobo]

Forgot to mention that a panel in which the parameters
could be entered both as you have them and ordered as the
affine transformation matrix would be appreciated by
most users. I think this is how ArcView has it (I do not
use it myself). I find this document useful:
www.quantdec.com/GIS/affine.htm

Agus

Agustin Lobo wrote:
> The problem with "Capture From Map Canvas" is
> that you need 2 canvas, unless both the original and the reference 
> objects are
> be very close. The Georeferencer plugin opens the raster to be
> processed in a special window, but that window does not
> let you display a vector. Perhaps that would be enough, a window
> such as the one in Georeferencer but for vectors.
> 
> By now, I'm going to try using Coordinate capture twice, once for the
> vector to be warped and the other for the reference object. Then
> input both sets of coordinates into R and calculate
> the affine transformation matrix there. Then I can either
> go on with the actual transformation in R (package spatstat)
> and then export to QGIS (this is comfortably done thanks to
> manageR) or use your plugin.
> 
> Agus
> 
> Maurício de Paulo wrote:
>> Hum... you mean like georreferencing the vectors?
>> While reading your mail I thought about a "Capture From Map Canvas" 
>> for the two translation coordinates.
>> Well, I don't know how the georreferencer is written, but I can try to 
>> think about reusing it's code. I'm going to take a look at it.
>> Thanks for the tip.
>> Best regards,
>> Mauricio de Paulo
>>
>> On Fri, Nov 27, 2009 at 9:36 AM, Agustin Lobo <aloboaleu at gmail.com 
>> <mailto:aloboaleu at gmail.com>> wrote:
>>
>>     Hi!
>>
>>     It's often the case in which you actually don't know
>>     the values for the affine transformation for
>>     plugin qgsAffine but just some pairs of corresponding coordinates.
>>     I understand that including a facility such as the one for raster
>>     georeference would be very useful but quite a work, thus I wonder
>>     if the raster georeference plugin could actually output this
>>     information which could then be fed to qgsAffine?
>>
>>     Agus
>>     --     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 <mailto:Agustin.Lobo at ija.csic.es>
>>     http://www.ija.csic.es/gt/obster
>>
>>
>