Re: Map Projections

[Jonathan Callahan <callahan@xxxxxxxxxxxxx>]

Jeremy,

The map projection capabilities of Ferret are described briefly in the version
4.9
release notes:

http://ferret.wrc.noaa.gov/Ferret/Documentation/Release_Notes/v490/#curvilinear_shade_and_fill

It is not clear from your email whether your data are stored in a rectangular
grid
or in a curvilinear (projected) grid.  If your data are stored in a curvilinear
grid you
can use the 3-argument SHADE command to plot the data in their raw form (ie.
in the curvilinear grid).  If your data are stored in a rectangular grid
(lat,lon) you can use
the map projection scripts to create output plots in any other map projection
(curvilinear grid).  It's also possible to plot curvilinear grid data in a
different
curvilinear projection.  I created an orthographic projection with both
rectangular
grid data (coads) and polar equal area sea ice data.  Notice in the Bering Sea
how
the two different grids are visible.

http://dread.pmel.noaa.gov/ferret/New_Features/gifs/ortho_globe.gif

To answer your questions more directly:

1) Does FERRET support these map projections?

If the data are stored in these projections: Yes, read about curvilinear
coordinates.

If the data are stored in rectangular coordinates:  If the projection you want
is not
supported by a mp_~ script, you can create it based on the projection scripts
provided.

2) Are the data first interpolated to a more standard grid and then plotted?

No, the data are plotted in their raw form.

Please don't hesitate to ask for assistance if this email doesn't answer all
your
questions.


-- Jonathan Callahan


Jeremy S Pal wrote:

> My research involves the use of a regional climate model. I use two
> different map projections with this model: (1) rotated Mercator projection
> (rotated to a pole other than the equator, say 40N) and (2) Lambert
> conformal projection (true at 30N and 60N).  Does FERRET support these
> map projections?  If so, are the data plotted in the raw form or are they
> first interpolated to a more standard grid and then plotted?  If not, how
> are the other regional climate modelers dealing with this issue?  Previous
> emails to the user support group indicate that these map projections are
> supported, however, it seems that they are only supported for special
> cases (e.g. Mercator with the equator as the pole).  I would appreciate
> any information on the matter.