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[GEMPAK #MGA-118138]: Filtering of the number of points in LINE

> Steve,
> 
> Thank you for your help on my problems on SFMOD.
> 
> I have a question on a slightly different subject.  It is about the way
> LINE plots contours.  Right now, I am using gdplot2 with DEVICE=vg to
> generate objectively analyzed isobars in a VGF file which can be opened
> and edited in NMAP.  The goal is to have the isobars smooth enough so
> that minimum amount of editing is required.  I've already set a couple
> of things to smooth the isobars.  They are:
> 
> 1. GDPFUN = SM5S(PMSL)
> 2. CONTUR = 9/1
> 3. LINE = 5/1/1-1/2/1

Kwan,

You might have better luck using a higher number of passes in CONTUR rather than
subboxes or SM5S()/SM9S(). I typically find something like CONTUR=3/3 provides 
a nice
amount of smoothing without losing the features of the data. Also note you
are misisng the "/" character before the "-1" in LINE above.

You can also set IJSKIP to subsample your data by every other point
such as IJSKIP=1.

Steve Chiswell
Unidata User Support


> 
> However, the resulting isobars are still not sufficiently smooth.  I
> could use SM5S more than once and get smoother isobars outside of high
> and low pressure centers.  However, some smaller closed centers are
> filtered away.  I could also increase the # of subboxes to e.g. 64/1
> and get smoother isobars.  But then they are broken up into smaller
> line segments (although they look like continuous lines in NMAP).  The
> next thing I do is to set the filter in LINE to 1 (max).  Compared with
> using 0 for the filter, less points are used to produce the line.
> However, there are still too many points used even at 1.  I think I'll
> need only about half of these points.  So I want to double the amount
> of point filtering.  But I can't set it to 2, right?  If I really want
> to do that, I'll have to change the filter program itself, right?
> 
> Kwan
> 
> 


Ticket Details
===================
Ticket ID: MGA-118138
Department: Support GEMPAK
Priority: Normal
Status: Closed