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[IDV #KWE-346293]: degrees_east > 180 plots off map!

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  • Subject: [IDV #KWE-346293]: degrees_east > 180 plots off map!
  • Date: Wed, 16 Apr 2008 09:52:23 -0600
Hi Rich-

> On Tue, Apr 15, 2008 at 5:30 PM, Unidata IDV Support
> <address@hidden> wrote:
> 
> >  It's really that the map lines go from -180 to 180 and the data
> >  goes from 0-360.  Depending on the projection, one will not
> >  line up.
> 
> Ah, okay.

Let me explain that a bit more.  The map projection from the
data is based on the range of the longitude values in the data.
In your case, you have values > 180.  The  map lines are in
-180 to 180.  So, the map projection is going to be to the
right of the map lines:

-180       180  200+(your area)

     map        data

However, when you change the data to be in the -180 to 180 range,
then both are within the same bounds.

(not sure if that clears it up or makes it more  confusing).

> >
> >  > If would be nice if IDV did this so I didn't have to!
> >
> >  That would be nice. ;-)
> >
> >  > http://stellwagen.er.usgs.gov/models/share/peru.ncml
> >
> >  That dataset only goes to about -160.  Is that the correct
> >  link?  I'm not sure I'm understanding the problem you are seeing
> >  with this example.
> 
> If you delete the line in the NcML where I overwrote the Longitude
> values you will see the problem.

I've put a check in there to see if the bounds of the map
projection fall within 0-360 or -180 to 180.  Based on that
I normalize all longitudes to fit in that range.  I've got
a lot of testing to do, but this might just work.  Thanks
for the suggestion.

Don


Ticket Details
===================
Ticket ID: KWE-346293
Department: Support IDV
Priority: Normal
Status: Open