[josm-dev] Geometric calculations and projections

[Robert Scott]

On Tuesday 08 December 2009, Matthias Julius wrote:
> What do you think?

It's funny you should say this - I am currently working on a few things such as some proper geometry operations.

It started with me doing some work on the extrude function and realizing it should really be able to work in real-space rather than projected-space. The way I was planning on doing this was to do the operation in in 3-space, in cartesian coordinates, then converting back to latlon.

However, the ability to also do the operation in projected-space is quite important I think, as users are often tracing from imagery, in which case they will probably want WYSIWYG behaviour on the projection. In this vein, the way I was planning on doing it was to have a modifier key (hmm most of them are already taken aren't they?) to select between 2-space(projection) calculations and 3-space(real) calculations.

One of the pieces of initial work would probably have been improving some of the datatypes like EastNorths, which make geometry operations pretty painful imho. We need more generic vector operations and perhaps even some 3-space vector types.

I'm currently working on some more options (in plain-old-2D) for the extrude mode, and I haven't actually started coding all this stuff.

Apart from extrusion I also thought the 'rotate' operation could do with ellipsoidally-correct calculations.


robert.