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

Markus Metz markus.metz.giswork at googlemail.com
Mon Oct 31 06:34:30 EDT 2011

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).
> 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.

Markus M

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