weird strippling/streaking pattern in a map

From: Jonathan Vigh (vigh AT XXXXXX)
Date: Tue Mar 23 2004 - 14:57:23 MST

Greetings All,

I am trying to make some publication-quality plots in NCL, but am
experiencing an odd strippling/streaking pattern when I output to
postscript or eps. I've reduced my plot down to a very simple
configuration (I plot a map using gsn_csm_map and resources for color
fill and boundary outlines). The strippling/streaking often appears in a
north-south oriented box, and sometimes other faint streaks appear going
from north to south. In the example plot attached, the streaking is
visible in a region to the north of Cuba. If I change the domain of the
map to a different region like India, the strippling also appears, so
perhaps the problem is related to the low-level area routines? If I just
plot over the open ocean, with no land in the domain, I think it goes

Maybe this is a bug in the NCL postscript drivers? My NCL version is
a031. (I was making similar plots previously using version a024 and I
don't think I had this problem, but I'm not sure.)

Interestingly, the strippling isn't visible using the Ghostscript viewer
(gs), but it is visible in Ghostview (gv). It's not just a quirk of
Ghostview, because when I convert (using convert) to another format like
png, the streaks are still visible. I've attached my script (test.ncl).
The output file is too large for this list, but I can e-mail it to any
of you off-list if you can't reproduce it with the script.

Has anyone experienced this before, and if so, do you know what the
problem is, or how to prevent this strippling?



Jonathan Vigh
Graduate Research Assistant
Schubert Research Group 
Department of Atmospheric Science
Colorado State University
vigh AT
"Research is formalized curiosity. It is
 a poking and prying with a purpose."
                  -- Zora Neale Hurston

;******************************************************** ; test.ncl ; ; The purpose of this script is to reproduce an apparent ; problem with the NCL/NCAR Graphics EPS driver. ; ;******************************************************** load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl" load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl" load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/shea_util.ncl" begin plottype = "eps" minlat = 0 maxlat = 50 minlon = -90 maxlon = -40 ;***** Define some NICE color maps to use. colors_6 = (/"White","Black","Black","GoldenRod1","PaleTurquoise3","Grey37", \ "MediumPurple1","Aquamarine2","LawnGreen","Red","VioletRed1", \ "DarkGreen","Magenta","DodgerBlue","Moccasin","Brown","RoyalBlue4","SteelBlue","Grey"/) ;******************************** ; create plot ;******************************** wks = gsn_open_wks(plottype,"test") gsn_define_colormap(wks,colors_6) ; Set the new colormap. res = True res@mpMinLatF = minlat res@mpMaxLatF = maxlat res@mpMinLonF = minlon res@mpMaxLonF = maxlon res@mpDataBaseVersion = "Ncarg4_1" ; Alias 'MediumRes' res@mpDataSetName = "Earth..1" res@mpFillOn = True res@mpOutlineOn = True res@mpOutlineBoundarySets = "AllBoundaries" res@mpLandFillColor = "Grey" res@mpInlandWaterFillColor = "SteelBlue" res@mpOceanFillColor = "SteelBlue" res@mpGeophysicalLineColor = "Black" res@mpGeophysicalLineThicknessF = 0.5 res@mpUSStateLineColor = "Black" res@mpUSStateLineThicknessF = 0.5 res@mpNationalLineColor = "Black" res@mpNationalLineThicknessF = 0.5 ;******************************** ; draw map ;******************************** plot = gsn_csm_map(wks,res) end

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