[ncl-talk] creating tile layers from ncl map images
Alan Brammer
abrammer at albany.edu
Thu Oct 9 17:19:42 MDT 2014
Heres a reply I sent to someone on a vaguely similar thread a little while
back. The number of images you plot increases quickly so above a zoom of ~
3 or 4 it can take a long time to work through them all. There may be
(probably is) a better way to do it but this worked for me. Haven't used it
for a while so it may not work the same in recent versions. Unfortunately
the ncl-talk archive machine has changed all the resources so you'll need
to do some find/replace to get it to work.
I believe there was a KML function development somewhere in the
archives of NCL talk. Not sure of the details there, but could be
worth a google.
I tested the tile idea a while back though and it was reasonably
successful. Though it can require a lot of images this way and can
therefore take a long time to plot them all up.
Below is my test script, I put together a while back to trial this
idea (using 6.1.2 at the time). The corners are the key part and are
based on coordinate info from this page, which is very helpful for
understanding how map tiling works, if you choose that route.
http://www.maptiler.org/google-maps-coordinates-tile-bounds-projection/
Good luck,
Alan.
undef("setlatlon")
procedure setlatlon(res, z,x,y)
begin
math_pi = 355/113. ; The Approx for pi I use. res at
mpLeftCornerLonF <http://mailman.ucar.edu/mailman/listinfo/ncl-talk>
:= x / 2^z * 360.0 - 180.0res at mpRightCornerLonF
<http://mailman.ucar.edu/mailman/listinfo/ncl-talk> := (x+1) /2^z *
360.0 - 180.0res at mpRightCornerLatF
<http://mailman.ucar.edu/mailman/listinfo/ncl-talk> :=
atan(sinh(math_pi * (1 - 2 * y / 2.^z))) * 180.0 / math_pires at
mpLeftCornerLatF <http://mailman.ucar.edu/mailman/listinfo/ncl-talk>
:= atan(sinh(math_pi * (1 - 2 * (y+1) / 2.^z))) * 180.0 / math_pi
end
undef("check_dir")
procedure check_dir(name)
begin
if(.not.isfilepresent(name)) ;; this should maybe be fileexists() now.
system("mkdir "+name)
end if
end
mpres = Truempres at mpLimitMode
<http://mailman.ucar.edu/mailman/listinfo/ncl-talk> =
"Corners" ; method to zoommpres at mpProjection
<http://mailman.ucar.edu/mailman/listinfo/ncl-talk> = "mercator"mpres
at mpPerimOn <http://mailman.ucar.edu/mailman/listinfo/ncl-talk>
= False ; turn off map perimetermpres at
mpOceanFillColor <http://mailman.ucar.edu/mailman/listinfo/ncl-talk> =
-1; "darkslategray1"mpres at mpInlandWaterFillColor
<http://mailman.ucar.edu/mailman/listinfo/ncl-talk> = -1;
"deepskyblue"mpres at tmXTOn
<http://mailman.ucar.edu/mailman/listinfo/ncl-talk> = Falsempres at
tmXBOn <http://mailman.ucar.edu/mailman/listinfo/ncl-talk> =
Falsempres at tmYROn
<http://mailman.ucar.edu/mailman/listinfo/ncl-talk> = Falsempres at
tmYLOn <http://mailman.ucar.edu/mailman/listinfo/ncl-talk> =
Falsempres at gsnMaximize
<http://mailman.ucar.edu/mailman/listinfo/ncl-talk>= Truempres at
mpGeophysicalLineThicknessF
<http://mailman.ucar.edu/mailman/listinfo/ncl-talk> = 2.mpres at
mpOutlineDrawOrder <http://mailman.ucar.edu/mailman/listinfo/ncl-talk>
= "PostDraw"mpres at mpOutlineBoundarySets
<http://mailman.ucar.edu/mailman/listinfo/ncl-talk> ="National"
; Turn on country boundariesmpres at mpFillOn
<http://mailman.ucar.edu/mailman/listinfo/ncl-talk> = False
wkst = "png"wkst at wkWidth
<http://mailman.ucar.edu/mailman/listinfo/ncl-talk> = 268 ; 256 with 6
pixels for a border which will get cut off.wkst at wkHeight
<http://mailman.ucar.edu/mailman/listinfo/ncl-talk> = 268 ;
dir = “/plotting_directory/“
do z = 2,4 ; Zoom level of maps.
check_dir(dir+z) ; make sure there is a directory to put the image in.
do x=0,(2^z)-1 ;
check_dir(dir+z+"/"+x+"/“) ; make sure there is a directory to
put the image in.
do y=0,(2^z)-1
wks = gsn_open_wks(wkst, dir+z+"/"+x+"/"+y ) ;; zoom/x/y.png
directory structure is how most tile based utilites expect them.
setlatlon(mpres, z,x,y) ;; Set corners of map based on zoom
level, X, and Y locations.
if(z.ge.4)
mpres at mpDataBaseVersion
<http://mailman.ucar.edu/mailman/listinfo/ncl-talk> = “MediumRes” ;;
personal preference on plotting time vs coast line representation.
end if
map = gsn_csm_map(wks,mpres) ;; create map.
system("mogrify -fuzz 2% -transparent white -shave 6x6
"+dir+z+"/"+x+"/"+y+".png”)
;; Call imagemagick to make background transparent (6.2. may have made
this redundant) and trim the 6pixel border that NCL loves ( may be
machine dependent );
end do ; y- loop
end do ; x-loop
end do ; z-loop
##############################
Alan Brammer,
PhD candidate,
Department of Atmospheric and Environmental Sciences,
University at Albany, State University of New York, Albany, NY,
12222abrammer at albany.edu
<http://mailman.ucar.edu/mailman/listinfo/ncl-talk><mailto:abrammer at
albany.edu <http://mailman.ucar.edu/mailman/listinfo/ncl-talk>>
##############################
On Thu, Oct 9, 2014 at 5:18 PM, Micah Sklut <micahs2005 at gmail.com> wrote:
> Hi,
>
> I was wondering if anyone has gone through the process of creating a tile
> image layer from your NCL maps to use in a web software application or
> otherwise?
>
> If so, what software did you use?
>
> Many of the popular mapping applications allow you to import your own tile
> layers, like Google Maps. I have been looking at the open source software
> leaflet - leafletjs.com. I am just struggling to find the most
> appropriate way to create the tile layer from my NCL images. For my
> purposes it has to be a command line tool for automation.
>
> As an example. Lets say I created a world wide map of precipitation. This
> map would be viewable on the global scale, and then navigated or zoomed
> into any area for greater detail.
>
> Thank you for any suggestions,
>
> --
> Micah Sklut
>
>
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