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Re: [ferret_users] Overplot track data

Hi Charlotte,
A couple of things. 

You're calling mp_mercator, but then not using the map projection coordinates that the mercator projection script creates when you draw the plot.  You'll want to use the 4-argument form of the vector command:

   !Plot the velocity field 
   vector/length=1/XSKIP=3/YSKIP+3/overlay U,V, x_page, y_page

The SET REGION/X=-90:-80  is getting in the way of reading the lon,lat data onto the "abstract" axis, which is just an axis of indices, 1,2,3,...  Try a CANCEL REGION command before accessing that data. To plot this data on top of your map projection plot, you might look at the script mp_polymark, which overlays locations as polygons on top of another plot

yes? go/help mp_polymark

Charlotte Girard wrote:
I would like to overplot a track on a current velocity field. I managed to plot the current velocity field alone, and also the track alone but I can't find a way to plot both of them!

My track data (longitude, latitude) are stored in an ascii file "track.res", with 2 columns. For instance:

-83.0    25.0
-84.0    28.0
-85.0    26.0

My programme looks like:


use "my_file.nc"    !file containing zonal (U) and meridional (V) speed

set region/x=-90:-80/y=20:35/z=0/t=10-Aug-2006
go mp_mercator
set grid U

!Plot the velocity field
vector/lenght=1/XSKIP=3/YSKIP+3/overlay U,V

!Plot the track
file/format=delim/var="lon,lat" track.res
list lon,lat
plot/line/over/color=red lon,lat

go fland 1


Ferret is not happy with the instruction "list lon,lat" and returns :

**ERROR: illegal limits: "LON" is not in the range X=-90:-80
    Axis extremes are X=0.5:20480.5
list lon,lat
Command file, commande group, or REPEAT execution aborted

Any suggestion?
Thanks for you help !



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Ansley Manke, NOAA/PMEL   ansley.b.manke@xxxxxxxx
7600 Sand Point Way NE, Seattle WA
Phone 206-526-6246,  FAX 206-526-6744

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