[ncl-talk] segments in shape must be closed circle?

[Sitan Heyl]

Hi, All
>
>    When I read the example 13 about shapefile (
> https://www.ncl.ucar.edu/Applications/shapefiles.shtml), I found one
> confused code as follow. my question is that if one geometry has two or
> more segments, need every segments be closed circle or polygon, if not, how
> can this code directly determine gc_inout in every segments?

;---Some Georgia counties have multiple segments
    startSegment = geometry(ga_counties(i), geom_segIndex)
    numSegments  = geometry(ga_counties(i), geom_numSegs)
    do seg=startSegment, startSegment+numSegments-1
      startPT = segments(seg, segs_xyzIndex)
      endPT   = startPT + segments(seg, segs_numPnts) - 1

;---Loop through each point on data grid and see if it's in this county.
      do n=0,nii_latlon-1
        nn = ii_latlon(n)     ; Get index of point we're checking
;
; This "if" statement speeds up code, by making sure we don't
; needlessly check a lat/lon point if:
;
; - we've already found it in another county
; - it doesn't fall within the general lat/lon box that covers this county
;
        if(skip_check(nn).or.\
           lat1d(nn).lt.min(lat(startPT:endPT)).or.\
           lat1d(nn).gt.max(lat(startPT:endPT)).or.\
           lon1d(nn).lt.min(lon(startPT:endPT)).or.\
           lon1d(nn).gt.max(lon(startPT:endPT)))
           continue
        end if

;---Here's the check if the point is in the county.
        if(gc_inout(lat1d(nn),lon1d(nn),\
                    lat(startPT:endPT),lon(startPT:endPT))) then
          data_mask_1d(nn) = 1    ; This point is inside this county
          skip_check(nn)   = 1    ; Don't check this point again
        end if
      end do

end do ; End of collecting points for this county

Best,
Yongli
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