Re: Creating 3D grid from scattered data

[Ansley Manke <ansley@xxxxxxxxxxxxx>]

Hi  Steve

Re Mike McCann's question -

The scat2grid*xy  functions are set up to inherit a time axis, but not a Z from the
third argument.  The reason is that the first three arguments (xpts, ypts, f(xpts,ypts))
are lists of points which may reside on any of the spatial axes.  One could change
the function to inherit a Z axis but it would require more checking of the arguments'
grids.
-Ansley


Steve Hankin wrote:

> hi Mike,
>
> Since it appears that you have only 5 points on your Z axis (?) there is a
> simple solution possible:
>
>     LET VZ0  = scatter2gridlaplace_xy( **arguments at Z=0** )
>     LET VZ25 = scatter2gridlaplace_xy( **arguments at Z=25** )
>     LET VZ50 = ...
>     LET VZ75 = ...
>     LET VZ100 = ...
>
>     DEF AXIS/Z=0:100:25/DEPTH  zaxis
>
>     LET V  = IF K[GZ=zaxis] EQ 1 THEN VZ0  ELSE V2
>     LET V2 = IF K[GZ=zaxis] EQ 2 THEN VZ25 ELSE V3
>     LET V3 = IF K[GZ=zaxis] EQ 3 THEN VZ50 ELSE V4
>     LET V4 = IF K[GZ=zaxis] EQ 4 THEN VZ75 ELSE VZ100
>
> Your variable "V" is now the function of Z that you desire.
>
> This approach is not the ideal solution. Ideally the function
> scatter2gridlaplace_xy() should inherit the Z axis from the arguments XPTS,
> YPTS, and F. In this case, as long as the variable you provide as "F" is,
> itself a function of Z, so, too will the result be. I suspect it was a simple
> oversight that the function does not work this way. We will look into fixing
> this. Note that the function *does* inherit correctly in this manner on the T
> axis.
>
>     - steve
>
> ===========================================================
>
> "McCann, Mike" wrote:
>
> > Hi,
> >
> > I have a set of scattered ocean observations that I'd like
> > to grid into a 3D volume.  The strategy I'm considering is
> >
> > 1. Create horizontal sections and grid to a level with
> >    scatter2gridlaplace_xy()
> >
> > 2. Assemble these sections into a 3D volume following the
> >    multiple-slab example:
> >
> > yes? DEF AXIS/x=1:360:1  xaxis
> > yes? DEF AXIS/y=1:180:1  yaxis
> > yes? DEF AXIS/Z=0:100:25/DEPTH  zaxis
> > yes? DEF GRID/X=xaxis/Y=yaxis/Z=zaxis uv_grid
> > yes? DEF AXIS/Z=0:0:1  zaxis1
> > yes? DEF GRID/LIKE=uv_grid/Z=zaxis1  uv_grid1
> > yes? FILE/GRID=uv_grid1/BAD=-999/VAR="u,v"  uv.data1
> > yes? LET/TITLE="My U data"  u1 = u[G=uv_grid]
> > yes? LET/TITLE="My V data"  v1 = v[G=uv_grid]
> > yes? SAVE/FILE=uv1_5z.cdf/KLIMITS=1:5  u1, v1
> > yes? CANCEL DATA uv.data1
> > yes? DEF AXIS/Z=25:25:1  zaxis1
> > yes? FILE/GRID=uv_grid1/BAD=-999/VAR="u,v"  uv.data2
> > yes? SAVE/FILE=uv1_5z.cdf/APPEND  u1,v1
> > . . .
> >
> > My problem is that I need to get the output of scatter2gridlaplace_xy()
> > onto a 3D grid where the Z axis is a single value.  How can I do this?
> >
> > I tried
> > SET VAR/GRID=newgrid <variable_from scatter2gridlaplace_xy()>
> > but I get an error.
> >
> > I think I can list the level out to an ascii file, then read it back
> > in onto the 3D grid, but I'd rather not have to do this.  Is there
> > a more efficient way?
> >
> > Thanks in advance,
> > Mike
> >
> > --
> > Mike McCann   (mccann@mbari.org)
> > Group Leader, Information Applications Group
> > Monterey Bay Aquarium Research Institute
> > 7700 Sandholdt Road
> > Moss Landing, CA 95039-9644
> > Voice: (831) 775-1769   Fax: (831) 775-1646 http://www.mbari.org/rd/iag.htm
>
> --
>
>                 |  NOAA/PMEL               |  ph. (206) 526-6080
> Steve Hankin    |  7600 Sand Point Way NE  |  FAX (206) 526-6744
>                 |  Seattle, WA 98115-0070  |  hankin@pmel.noaa.gov

--
Ansley Manke  Pacific Marine Environmental Laboratory  Seattle WA  (206)526-6246