[Qgis-developer] georeferencer plugin - map follow mode

[Manuel Massing]

Hi Maxim,

> Manuel, I've read provided links twice, but still not following ;)
> "map follow" discussion in regard to Georeferencer. Can you
> explain?

The basic idea is to use the GCP-derived transforms to show the same
viewport in the qgis main canvas and in the georefencer canvas.

Now that I have reread Maciek's posting, I am also not sure anymore
he described the same, so sorry if I confused you all :-)

What I have currently done is encapsulating the different parametrised
transform methods (linear, helmert, the gdal based polynomial/tps) and
associated parameter fitting in GeorefTransformer classes - this is mainly
some refactoring to avoid code duplication and special cases for the
different transforms. A GeorefTransformer instances provide methods to
fit parameters to the GCPs, and then can be used to transform
either the main canvas viewport into raster coordinates or vice versa, based
on this parametrisation. I want to add checkboxes which give you the option to
link the georeferencer viewport to the main viewport (and vice versa). 

This is very useful if you reference a raster to a data source in
the main canvas (e.g. when referencing a scanned street map against a 
road vector layer), and already have a good approximation of the final
transform. Often you only need to add local refinements to bring the residuals
down (especially if you using local interpolation methods like TPS, or a high 
order polynomial), and such linked viewports will aid immensly in finding
correspondencies faster.
The transformer classes are also useful to report residuals for the
choosen parametrisation. 

> Also, please try to coordinate your patches it with us, as there are some
> more additions sitting in our georeferener SVN.

Is this the repository at http://svn.gis-lab.info/qgis-gdal-georef/?

I am currently developing against qgis trunk. Should I update
to your repository?  I will unfortunatly have a larger patchset than
anticipated - but given the small codebase, merging wouldn't present a problem 
I guess (if/when this feature is up for inclusion).

Hope I clarified the idea a bit.

bye,

	Manuel