[GRASS-user] using a vector map as target map for raster map to georectify

Moritz Lennert mlennert at club.worldonline.be
Mon Oct 31 08:27:45 EDT 2011

On 31/10/11 11:34, Markus Metz wrote:
> On Mon, Oct 31, 2011 at 11:22 AM, Moritz Lennert
> <mlennert at club.worldonline.be>  wrote:
>> On 31/10/11 10:08, Markus Metz wrote:
>>> On Sat, Oct 29, 2011 at 11:25 AM, Moritz Lennert
>>> <mlennert at club.worldonline.be>    wrote:
>>>> On 27/10/11 21:10, Moritz Lennert wrote:
>>>>> Hello,
>>>>> Trying to use the georeferencing tool in 6.4.1, I have the following
>>>>> question: is it possible to define a vector map as target map when
>>>>> georeferencing a raster map ? I can't seem to find how to do this.
>>>> Just to be precise: I'm talking about the tool in the wxgui.
>>>> Am I the only one seeing this as a problem ? I can work around this by
>>>> transforming my vector map in a raster and then use the result as target
>>>> map. But I find this less than ideal. It should be possible to use vector
>>>> map as reference, not only raster maps.
>>>> I will file a bug report about this, but was just wondering whether I'm
>>>> missing something obvious.
>>> Vector support in the georeferencing tool is poor. Ideally the tool
>>> would have something like a layer manager where you can add as
>>> reference maps any number and combination of raster and vector maps,
>>> just like in the regular layer manager. Further more, the C module
>>> v.rectify is still missing (I want to write it based on v.transfrom
>>> and v.proj but did not get around yet to do it).
>> Ok, so currently I have to use the v.to.rast workaround, then. But does the
>> solution really have to be a whole layer manager ? Generally one does not
>> use many different layers as reference maps, so just having a choice between
>> vector and raster reference maps in the preparatory steps of the tool should
>> be enough IMHO.
> OK. Then the option for reference maps could be one raster map and/or
> one vector map (vector map always on top of raster map).

This sounds good to me.

>> v.rectify is still another issue. v.transform probably covers most of the
>> use cases anyway, or ?
> Yes, apart from the case when source and target LOCATION_NAME are
> different. This is handled by v.proj. Since GCPs are specific for a
> given source / target location combination, a TARGET like for imagery
> groups would also be needed.

I think that in many cases you can import the data directly into your 
target location and run v.transform there. This is less the case for 
raster data. But I agree that the possibility should be there for the 
user to georeference vector data between two different locations.


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