[GRASSLIST:5962] Re: Krovak / PROJ4 (+axis option?)

[H Bowman]

> > as you probably know, Krovak defines X=-y, Y=-x, i.e. X is vertical
> > axis, oriented down and Y is horizontal oriented to the left. But
> > all GIS/GPS/... systems must use usual coordinate system where 
> > coordinates are in 3. quadrant.
[...]
> > 
> > Radim
> > 
> 
> Something along the line of a +axis switch, where "+axis=en" means
> that x axis = 'e'ast, and y axis = 'n'orth.  Then a coordinate system
> string could specify alternate axis orientations as +axis=sw
> indicating that X is a "southing" (or negative northing) and Y is a
> westing (or negative easting).  I think this would be the right
> organization for Krovak right?

Hi - just to point out how Matlab handles this issue, which always made
good sense to me when I have needed to do this sort of thing on
occasion:

    AXIS IJ  puts MATLAB into its "matrix" axes mode.  The coordinate
       system origin is at the upper left corner.  The i axis is
       vertical and is numbered from top to bottom.  The j axis is
       horizontal and is numbered from left to right.
    AXIS XY  puts MATLAB into its default "Cartesian" axes mode.  The
       coordinate system origin is at the lower left corner.  The x
       axis is horizontal and is numbered from left to right.  The y
       axis is vertical and is numbered from bottom to top.
[(c) Mathworks 199something I suppose]


I find thinking of it this way requires less mental gymnastics than
trying to visualize rotated planes, which in turn makes debugging a lot
more straight forward.



regards,
Hamish