Re: native mercator projection still having problems.

John,

I think you need to set mpCenterLonF as well, to a value between your
minLon and maxLon:

resources.mpCenterLonF = (maxLon-minLon)/2.

--Mary

On Oct 7, 2008, at 11:14 AM, Ertl, John C CIV 63134 wrote:

> Classification: UNCLASSIFIED
> Caveat (s): FOUO
>
> Mary,
>
> Thanks for the help. Yes the grid is a native mercator grid so I
> do not want to do any transforms. I have the data plotting but the
> map does not line up with the grid. The date is plotting for the
> western Pacific but the map is most of the globe...see attached. I
> am having the same kind of problem with the Lambert Conformal.
>
> For the west pac grid the max/min Lon/Lat
>
> latMin = -7.31
> lonMin = 94.8
> latMax = 51.735433
> lonMax = -174.616947
> I haver also tried lonMax = 185.383053
>
> Thanks again for the help
>
> PyNGL code
>
> #### Uses PyNGL to view/image feilds.
> wks = Ngl.open_wks(self.outPutType,fileName,None)
>
> #### This is set to allow very "buisy" contour plots to
> #### to be made.
> ws_id = Ngl.get_workspace_id()
> rlist = Ngl.Resources()
>
> rlist.wkColorMap = colorScale
>
> rlist.wsMaximumSize = 90000000
> Ngl.set_values(ws_id,rlist)
>
>
> Ngl.set_values(wks,rlist)
>
> resources = Ngl.Resources()
>
> resources.mpGeophysicalLineThicknessF = 3.
>
> ## Automaticly set the contour levels or use set vlaues to
> contour
> if contourMethod.upper() == "AUTO":
> resources.cnLevelSelectionMode = "AutomaticLevels"
> else:
> resources.cnLevelSelectionMode = "ManualLevels"
> resources.cnMinLevelValF = minValue #
> contour levels.
> resources.cnMaxLevelValF = maxValue
> resources.cnLevelSpacingF = interval
>
> if self.projection == "mercator":
> # set the map view to only show the grid region.
> resources.mpProjection = "Mercator" # projection
> resources.mpLimitMode = "Corners" # method to zoom
>
> resources.mpLeftCornerLatF = self.minLat
> resources.mpLeftCornerLonF = self.minLon
> resources.mpRightCornerLatF = self.maxLat
> resources.mpRightCornerLonF = self.maxLon
>
> resources.tfDoNDCOverlay = True # do not change data
> plot
>
> print "latMin = %s" % self.minLat
> print "lonMin = %s" % self.minLon
> print "latMax = %s" % self.maxLat
> print "lonMax = %s" % self.maxLon
>
> resources.tiMainFontHeightF = .015 # Main
> title font size
> resources.tiMainJust = "CENTERCENTER" # Main
> title justification
>
> resources.tiMainString = title
>
> resources.cnFillDrawOrder = "Predraw" # Draw
> contours first.
>
>
> if colorFill == "True":
> ##print "In color fill"
> resources.cnFillOn = True # Turn on
> contour fill.
> resources.cnLinesOn = False
> resources.cnLineLabelsOn = False # Turn off
> line labels.
>
> # if colorFill = false then plot with contours only
> elif colorFill == "False":
> ##print "In contour"
> resources.cnFillOn = False # Turn off
> contour fill.
> resources.cnLinesOn = True
> resources.cnLineLabelsOn = True # Turn on
> line labels.
> resources.cnMonoLineColor = False # Allow
> multiple colors for contour lines.
> else:
> # plot both contour and color fill.
> resources.cnFillOn = True # Turn on
> contour fill.
> resources.cnLinesOn = True
> resources.cnLineLabelsOn = True # Turn on
> line labels.
> resources.cnMonoLineColor = False # Allow
> multiple colors for contour lines.
>
>
> resources.cnInfoLabelOn = False # Turn off
> info label.
>
> resources.lbPerimOn = False # Turn off
> label bar perim.
> resources.pmLabelBarSide = "Bottom" # Change
> orientation of
> resources.lbOrientation = "Horizontal" # label bar.
> resources.lbLabelAngleF = 90
>
> try:
> map = Ngl.contour_map
> (wks,self.grid,resources) # make the plot
> Ngl.destroy(wks)
> except:
> print "sorry %s could not be made" % title
>
> John Ertl
> Meteorologist
>
> FNMOC
> 7 Grace Hopper Ave.
> Monterey, CA 93943
> (831) 656-5704
> john.ertl_at_navy.mil
>
> Classification: UNCLASSIFIED
> Caveat (s): FOUO
>
> From: Mary Haley
> Sent: Tue 10/7/2008 7:34 AM
> To: Ertl, John C CIV 63134
> Cc: pyngl-talk_at_ucar.edu
> Subject: Re: native mercator projection still having
> problems.
>
> John, To back up for a bit, is your data already on a mercator
> grid? I'm assuming it is, as that's what I think of when I hear
> "native mercator grid". If this is the case, then you need to make
> sure you have the map projection resources set up exactly to match
> the projection that the grid is defined on. Then, you do *not* want
> to set the sfXArray/sfYArray resources, and instead, set
> "tfDoNDCOverlay" to True. This tells PyNGL not to put your data
> through the equations for a map projection, because they are
> already projected. We do actually have an example of this. The
> pynglex example "panel2" is done on a native mercator grid, but
> oddly, it uses the sfXArray/sfYArray route, rather than the
> tfDoNDCOverlay route. Try running: pynglex panel2 and then modify
> panel2.py to change the lines: res.sfYArray = lat # Where to
> overlay res.sfXArray = lon # contours on map to: #res.sfYArray =
> lat # Where to overlay #res.sfXArray = lon # contours
> on map res.tfDoNDCOverlay = True # don't put data through # map
> projection equations and rerun. You will see that you get the same
> results, and this is because the mercator projection is set up to
> match the data exactly. I think I need to change this example to
> reflect that the sfXArray and sfYArray resources are not needed
> (this is a bit of overkill). --Mary On Mon, 6 Oct 2008, Ertl, John
> C CIV 63134 wrote: > Classification: UNCLASSIFIED > Caveat (s):
> FOUO > > Seth, > > Thanks for the help...The mercator projection
> looks to still have big problems but I was able to make a good step
> forward on the Lambert Conformal. > > I think it is plotting the
> data correctly but the map is very wrong. It looks to be showing
> the entire northern hemisphere map (in a Lambert conformal plot)
> but the data is only for a portion of the east pacific. What are
> you using for plotting the map on top of the data? > > Thanks for
> you help. > > John Ertl > Meteorologist > > FNMOC > 7 Grace Hopper
> Ave. > Monterey, CA 93943 > (831) 656-5704 > john.ertl_at_navy.mil > >
> Classification: UNCLASSIFIED > Caveat (s): FOUO > > > > From: Seth
> McGinnis > Sent: Fri 10/3/2008 3:58 PM > To: Ertl, John C CIV
> 63134; pyngl-talk_at_ucar.edu > Subject: Re: native
> mercator projection > > >> I have some old PyNGL code that displays
> Spherical grids and it works great. I want to now display native
> mercator and eventually Lambert grids. > > I don't know how a
> native mercator grid works, but for Lambert grids, here's the chunk
> of (NCL) code I use to define the map projection. ("proj" is a
> variable from my NetCDF file that holds the projection
> information.) > > res_at_mpProjection = "LambertConformal" >
> res_at_mpLambertMeridianF = proj_at_longitude_of_central_meridian >
> res_at_mpLambertParallel1F = proj_at_standard_parallel(0) >
> res_at_mpLambertParallel2F = proj_at_standard_parallel(1) >
> res_at_tfDoNDCOverlay = True ;; Lambert Conformal generally needs this
> > > For all the other projections I've worked with (polar
> stereographic, transverse mercator, and rotated pole), you just
> have to set the "mpCenterLatF" and "mpCenterLonF" attributes. So if
> lat looks correct but lon is off, my guess would be that you need
> to set resources.mpCenterLonF to something non-default. > > Cheers,
> > > Seth McGinnis > Associate Scientist > ISSE / NCAR >
> <COAMPS_W_PACw_pac_nest2_comp2ht_sfc2.020081007000>

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Received on Tue Oct 07 2008 - 14:59:41 MDT