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20040902: topography and map, attn: Don Murray

>From: NATHAN LOUIS UHLENBROCK <address@hidden>
>Organization: SSEC
>Keywords: 200409021500.i82F0o8E005713 IDV 3D map

Hi Nate-

>Tom recently sent me a bundle of a fantastic 3D topography map of North
>America that he got from you (I think). I am writing to see if you know
>of any way to make the map layer (the one that shows state boundaries,
>etc) lay directly on top of the 3D topography so that the boundaries
>follow the heights. I would like to do this so that when I rotate the
>view, the state boundaries appear to be in the correct spot instead of
>floating above the topography. 

First, load in a map data source.  You can do this by opening in the
File chooser a McIDAS map (OUTL*) that covers the area of your grid.  
Alternatively, the following maps are available via URL:

USA:
http://www.unidata.ucar.edu/content/software/idv/data/OUTLUSAM

WORLD:
http://www.unidata.ucar.edu/content/software/idv/data/OUTLSUPW

US counties:
http://www.unidata.ucar.edu/content/software/idv/data/OUTLSUPW

Next, load in your grid with the topography.

Now, from the Formula data source, expand the System Field category
and chose the 3D Map formula.  For the display, choose Topography,
then click the Create Display button.

You will be prompted for two fields - the map lines and the topography.
Choose the appropriate Fields for those two choices, then (like magic)
you should have a 3D map resampled to your topography grid.

A couple of notes:

1) I would turn off the Reset projection with new data button under the
Projections menu.  Since the resampled map may contain points that lie
over the dateline, the projection can be problematic.

2) The map may be obscured by the topography sometimes depending
on the resolution of the grid.

3) I hope to make this a little easier in a future release, possibly
allowing this from the MapDisplayControl.  The big issue is what to
use as a topography dataset.  I was going to use the Vis5D dataset,
but I have problems reading that in (and it's huge).

>Also, any word from the NCDC folks about
>the units issues with NOMADS? Thanks for the help!

The prospect is not good in the short term.  We are going to work
with the NCDC folks through the THREDDS project to add in the necessary
metadata.  Unfortunately, the person who did all the work on the
GrADS/DODS server which is serving up the data in no longer at COLA
(which produces grads).

Don
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