[GRASS-user] Problems running g.gui.gcp

[Johannes Radinger]

On Fri, Oct 23, 2015 at 11:19 AM, Moritz Lennert <
mlennert at club.worldonline.be> wrote:

> On 23/10/15 10:56, Johannes Radinger wrote:
>
>>
>>
>> On Fri, Oct 23, 2015 at 10:17 AM, Moritz Lennert
>> <mlennert at club.worldonline.be <mailto:mlennert at club.worldonline.be>>
>> wrote:
>>
>>     On 22/10/15 16:25, Johannes Radinger wrote:
>>
>>         Dear GRASS users,
>>
>>         Today I wanted to try the georectification tool g.gui.gcp in
>>         GRASS 7 for
>>         the first time. I was basically following the description on the
>>         GRASS
>>         wiki (https://grasswiki.osgeo.org/wiki/Georeferencing). In
>>         particular, I
>>         have a photograph from my camera with known reference points
>> which I
>>         load into an unprojected XY location. My target location should
>>         also be
>>         a XY location as the picture is taken from a "virtual" coordinate
>>         system. Inside my target XY-location I try to open g.gui.gcp and
>>         select
>>         raster, and the location and mapset where my photograph is
>>         stored. When
>>         I want to click next I get following error/message: "You must
>>         select a
>>         valid location and mapset in order to continue" and I can't
>>         proceed with
>>         the rectification. Just this GUI message appears, no
>>         error/warning in
>>         the grass console etc. I am puzzled how to interpret that? What
>>         is wrong
>>         with the location/mapset? The mapset I've selected is existing
>>         (I can
>>         select it from the dropdown menu). I tried to select any other
>>         location/mapset but receive always the same message.
>>
>>
>>
>>     Georectification is for georeferencing to a projected system. It
>>     does not make sense to georeference to an XY-location.
>>
>>     I see two options for you:
>>
>>     - Import you image directely into the target region and use r.region
>>     to adjust its boundary coordinates
>>     - Define your own projection system to fit your needs.
>>
>>
>> So far as I understand georectification and orthorectification in
>> particular is to rectify a picture/photo/image based on spatially
>> defined ground control points which might not be done by just adjusting
>> the boundary coordinates. BTW I also tried the European LAEA coordinate
>> system (EPSG 3035) as a target location which is not working either here
>> in my machine/setup (same message as already mentioned). Here
>> (https://www.dropbox.com/s/snjzd8eu7b8115k/2015-10-22%2015.26.30.jpg?dl=0
>> )
>> you can find a a photo (*.jpg) which is an "areal" photo with known 3d
>> coordinates for the single points (ground control points). I think this
>> example clarifies and illustrates what I intend to do and why the target
>> system can also be a XY location in my opinion. A rectification of this
>> image should make the lines of the grid more or less parallel. Or do I
>> get something completely wrong?
>>
>
> Actually, I was wrong: I don't get any complaint trying to use g.gui.gcp
> to georectify from XY to XY. So there seems to be an issue with your XY
> locations.
>
> Have you tried recreating the locations from scratch ?


Your results look really reasonable.... that's what I was looking for...

Actually, both XY locations are created from scratch (via the location
wizzard)
I get following output for both XY locations:

g.proj -p

XY location (unprojected)

I tried to start the GCP manager from within different other locations
(e.g. laea, datum: etrs89) and selecting different source location (e.g.
WGS84)....however I always get the same message. So I guess this is not
specifically related to my location but rather to the GCP manager/WX GUI?
As I don't get an error message it is difficult to judge what is going
wrong in my case...

I just looked up the source code and the error message seems to be related
to follwoing line:
https://trac.osgeo.org/grass/browser/grass/branches/releasebranch_7_0/gui/wxpython/gcp/manager.py#L399
As far as I understand, this error message is only given if no
 location/mapset is provided; however that is not the case here. Maybe my
selection of the location/mapset via the GUI does not get parsed
further....?

Strange that orthorectification from one XY to antother XY location works
on other machines but not on mine.

PS: As an important side note: I am working on Ubuntu which is installed on
a virtual machine (VMWare) on our server. I remotely connect to this
virtual machine via RDP.


>
> Moritz
>
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