[josm-dev] Validator plugin WronglyOrderedWays false error

[Martijn van Oosterhout]

On Sun, May 11, 2008 at 9:58 AM, Roy Rankin <rrankin at ihug.com.au> wrote:
> I have done a rewrite of the code as follows:
>
>  Determine the mean latitude of the closed way.
>  Then add the deltas of longitude for each segment starting with
>  a latitude greater than mean and subtract the deltas of longitude
>  if the start is less than the mean latitude.
>
>  The result should be positive for clockwise ways and negative
>  for counter-clockwise ways.

You're almost there. You should just use the proper formula for the
area of a polygon:

for each node
  area += x*deltay - y*deltax

Dont' need to calculte the mean, nor test anything for direction. And
100% relaible (for non-self-intersecting polygons anyway).

Have a nice day,
-- 
Martijn van Oosterhout <kleptog at gmail.com> http://svana.org/kleptog/