Time for another gPoly status update, today I have made some good progress on the tool again. The first part I have finished is the display of the GeoTIFF background image, this code seems to be quite optimal now, so that even with big images you can pan and zoom without too much delay. What I still have to do is verify the accuracy of the geo position, I think I need to render some reference information (of which I know the position) over it to do this. Another related feature on the todo list is the ability to make images georeferenced when they are not yet.
Today I also worked quite a bit on the user interface, especially the part that allows you to manipulate the layers in the project. Each layer can hold a background image or a set of features (polygons, lines, etc). Below is the screenshot of the current status.