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20000720: GINI to netCDF (cont.)

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  • Subject: 20000720: GINI to netCDF (cont.)
  • Date: Thu, 20 Jul 2000 14:23:38 -0600
>From: David Harper <address@hidden>
>Organization: NCAR/RAP
>Keywords: 200003012325.QAA04248 McIDAS-X GINI netCDF

Dave,

>I put a gif of the netcdf file in 4dwx-dev:/home/mcidas/G10_07191645_cdf.gif.

Got it, thanks.

The first thing that strikes me about this display is that the image
has been reprojected so that lines of constant latitude are horizontal
and lines of constant longitude are vertical.  McIDAS refers to this as
a RECTilinear projection.  The netCDF rendition of the GINI image
should not change the projection of the image.  Rather, it should
simply fill in the latitude and longitude values for each data point
using the navigation module that for the original projection (which is
Lambert Conformal tangent cone).

To demonstrate my assertion that your image has been reprojected, compare
it with:

http://www.unidata.ucar.edu/staff/tom/whiterect.gif

This is the result of a McIDAS remapping of the AREA copy of the
original GINI image into RECTinlinear navigation.  Notice how the
southern border of NM is horizontal.

>Notice the image fills out the whole grid.  If my end were sifting the image I
>would expect to see zeros on the North-East side.

The display in the GIF file does not represent all of the image that is
created by the imgcopy.k in your vis_convert.sh file.  That operation
creates an image that is 800x800 in size.  Your entire GIF display is
870x806 and a good portion of it sorrounding the displayed image is filled
with annotations.  I think that there is enough of the full image missing
that the image could be shifted by half a degree without you seeing zeros
on the North-East side.

Tom

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I see.  I had assumed the lat/lon was squared.  Our image is actually
rotated not shifted.  I'll have to give that one a lot of thought.
Zebra wants single arrays for the lat/lon values.

-Dave