[ncl-talk] gc_clkwise problem

Dave Allured - NOAA Affiliate dave.allured at noaa.gov
Wed Oct 26 20:11:18 MDT 2016


NCL support,

I am using NCL 6.3.0 on recent versions of both Mac OS and Linux.
 gc_clkwise returns the wrong value for this simple clockwise polygon:

ncl 1> lats=(/8,15,5,0/)
ncl 2> lons=(/38,130,130,38/)
ncl 3> print (gc_clkwise(lats,lons))
(0) False

However, the correct value is returned for the same polygon, with the order
of coordinates simply rotated by one position:

ncl 4> lats=(/0,8,15,5/)
ncl 5> lons=(/38,38,130,130/)
ncl 6> print (gc_clkwise(lats,lons))
(0) True

This may be related to a similar gc_clkwise problem that was assigned to JIRA
NCL-1699.  Please add this case to that ticket.  Thank you.

--Dave
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