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Re: Longitude weirdness


One comment in line below..


Steve Cousins wrote:
Hi Joe,

On Fri, 27 Jun 2003, Joe McLean wrote:

Is the longitude axis a regular or irregular axis (equal or unequal steps)?  In
Ferret you can tell by opening the data set and using the command "show grid


name             axis                        # pts    start                  end
xaxis name    LONGITUDE          180mr   21E                  19E(379)

next to # pts 180, 'm' means modulo and 'r' means regular (i means
irregular).  The fact that your XML file does not have the arange tag,
but rather the <v>20.140625</v> format, tells me LAS thinks it is
irregular, but this may be a precision issue within addXml.pl.  The
first two steps are each 0.2812, it may be regular.

Ferret shows LONGITUDE as mi so it is modulo irregular.  However, it does
appear to actually be a regular grid with points every .28125 degrees

Since the axis in the NetCDF file is modulo, it wouldn't matter which start point
you use in the XML axis definition.
if the axis is irregular, subtract 20 from all of the <v>.....</v> entries.

If the axis is regular, you can define your axis in the XML file like this:

   <mf1_11b_19990515_nc_longitude units="degrees" type="x">
       <arange start="0.0" step = "0.2812" size="1280"/>

In fact, try it this way first (less editing) and see if you like the way LAS

That works!  I used a step of 0.28125 and it works very well. Should I
just count on hand editing this? It isn't a big deal.  I don't think there
will be that many data sets.  I will be creating the netCDF files so if
there was something I could put in there to help trigger the make file to
do this then that would be ideal but either way I'm just glad something

I think it would be easier at this time to hand edit the axis definition(s) in your data config xml.

By the way, starting the the longitude values at 20 E is for drawing the world by
bisecting Africa at the left and right sides of a plot window, keeping ocean basins

Makes perfect sense now.

Thanks very much for your help with this.



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