Hi Martin,
On 2020/03/31 23:26, Martin Dobias wrote:
Hi Nyall
On Fri, Mar 13, 2020 at 8:45 PM Nyall Dawson <[email protected]> wrote:
On Sat, 14 Mar 2020 at 01:13, Martin Dobias <[email protected]> wrote:
1. Georeferencer opens in a new window. In order to see the main map
canvas and the georeferenced layer side by side, it is necessary to do
some resizing of windows which is inconvenient. It would be maybe more
practical to have the georeferenced image in a dock widget in the main
window - and all georeferencer related map tools included in the main
QGIS window as well. (Or maybe the other way around - to keep
georeferencer as a separate window, but allow the main map canvas to
be embedded in it?)
I would personally prefer the second option. I think a significant
amount of users doing regular georeferencing would have dual screen
setups (or large screens) and would appreciate having the a larger
georeferencer window then a dock would allow.
I have been thinking about this and what are the pros and cons of
having a separate window for georeferencing vs doing georeferencing in
main map canvas. Actually rather than discussing whether to have one
or two windows, the key bit to decide on is something else - what
would be the coordinate system of the georeferencer canvas:
A. image coordinates - that is what we have in QGIS georeferencer now:
the image gets loaded without any distortion and stays that way all
the time. Picking of map coordinates for GCPs has to be done in a
separate map canvas. (i.e. one click in "georeferencer canvas", and
one click in "reference map canvas")
B. map coordinates - that is what ArcGIS does. The image is placed at
some initial position in the map, picking of image coordinates and map
coordinates for GCPs is done in the same map canvas. (i.e. two clicks
in single map canvas)
The option B has the advantage that it is quite easy/intuitive to have
live preview of the image transformation as GCPs are being added. With
option A the live preview of the transform is not really possible (we
are still in image coordinates) - and the preview would need to be in
a separate map canvas.
While I like the live preview of option B, I find this option difficult
to use when georeferencing the raw image against a raster dataset such
as an aerial photograph. The top raster in the drawing order, e.g. the
raw image, covers the bottom raster as the live image transformation
proceeds, requiring the top raster to be toggled on/off when identifying
GCPs. In this case I find the current dual window approach is better as
the images can be placed side-by-side for easier identification of GCPs.
So where I am hesitating is whether to stick to option A which is
probably familiar to QGIS users - or with option B that may provide
better UX thanks to the live update of the warped raster (or vector).
I guess we will need to choose one or the other - supporting both
options would be probably too confusing. I am trying to figure out
which way to take, because this will also have great impact on the
workflow on how GCPs would be picked on the map(s) using map tools...
Thanks for your thoughts :-)
Cheers
Martin
_______________________________________________
Regards, Frank.
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