On 10/31/2013 5:37 PM, Ghansham Sangar
wrote:
Thanks a lot sir...
That means it is supported in ferret. Am i right in saying
that? I am using version 6.84.
Regards
Ghansham
Yes, Discrete Geometries datasets are supported in Ferret.
Data that is organized on rectiliner grids have simpler means of
doing graphics and analysis, such as simply opening a dataset and
issuing a VECTOR command to make a plot; and one can easily do such
things as area averages and integrals. The support of Discrete
Geometries datasets is less complete than for gridded data. However
there are methods for handling discrete geometries data as well.
In addition to the graphics commands I discussed yesterday, point
data and other non-gridded data is discussed in Chapter 8 of the
Ferret Users Guide.
http://ferret.pmel.noaa.gov/Ferret/documentation/users-guide/working-with-special-data-sets/
That chapter does not include discussion of the Discrete Geometries
definitions in the CF standard, but the first several sections
correlate to these file types.
Ansley
On Friday, November 1, 2013, Ansley Manke wrote:
Hi Ghansham, and all,
After a couple of messages off -line, I'd like to show some
things that we can do with point data such as this, if we're
interested in vectors. I've attached the files that the
script makes.
The dataset has lists of locations, times and variables.
It's a feature_type = "point" dataset in the Discrete
Geometries definitions of the CF standard.
http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.6/cf-conventions.html#appendix-examples-discrete-geometries
yes? show data
currently SET data sets:
1> ./sample.h5 (default)
name title
I J K L M N
LATITUDE latitude
1:7170 ... ... ... ... ...
LONGITUDE
longitude
1:7170 ... ... ... ... ...
MEAN_BT Average Brightness Temperature
1:7170 ... ... ... ... ...
MIN_BT Minimum Brightness Temperature
1:7170 ... ... ... ... ...
OBSERVATION_TIME
Time of Observation
1:7170 ... ... ... ... ...
PIXELS Corresponding Image Pixel
1:7170 ... ... ... ... ...
PRESSURE Pressure
1:7170 ... ... ... ... ...
QUALITY_INDICATOR
Wind Retrieval Quality Indicato
1:7170 ... ... ... ... ...
SCANS Corresponding Image Scan
1:7170 ... ... ... ... ...
UCOMP U Component of Wind Speed
1:7170 ... ... ... ... ...
VCOMP V Component of Wind Speed
1:7170 ... ... ... ... ...
WIND_DIRECTION
Wind Direction
1:7170 ... ... ... ... ...
WIND_SPEED
Wind Speed
1:7170 ... ... ... ... ...
! Get an idea of the data locations with a PLOT/VS
command.
! The RIBBON plot lets us color the locations
by any variable.
yes? plot/vs/ribbon/symbol=23/palette=rainbow
longitude, latitude, wind_speed
yes? go land thick
yes? frame/file=points.gif
! Make a vector plot, using the filled-polygon method.
That's explained here,
!
http://ferret.pmel.noaa.gov/static/Demos/polygon_vector_arrows/poly_vec_demo.html
! First draw a land underlay, using the lon/lat
region from the ribbon plot above,
yes? go basemap x=0:155 y=-72:68 20
! Set up for a polygon arrow plot. The script
writes the lines starting with ***
yes? go poly_vectors longitude, latitude,
ucomp, vcomp, 50 "arrow"
*** POLY_VECTORS: Issue commands such as follow
to plot the vectors ***
*** POLYGON/OVER/NOLABEL/KEY/NOAXES/LINE
PLT_X_ARROW, PLT_Y_ARROW, MY_VALUES[J=1:7170] ***
*** SET REGION SAVE ***
! Draw the arrow plot, coloring it by wind speed. The
color-by variable needs to be on the Y axis.
! Also add a label.
yes?
POLYGON/OVER/NOLABEL/KEY/NOAXES/LINE/pal=rainbow
PLT_X_ARROW, PLT_Y_ARROW, ysequence(wind_speed)
yes? LABEL/nouser `($ppl$xlen)/2`
`($ppl$ylen)+0.5`, 0, 0, 0.12, Colored by wind speed
(`wind_speed,return=units`)
yes? frame/file=arrows.gif
! Now try the other style of polygon vector plots,
"stick" vectors.
! We'll color these by another variable.
yes? go poly_vectors longitude, latitude,
ucomp, vcomp, 50 "stick"
yes?
POLYGON/OVER/NOLABEL/KEY/NOAXES/LINE/pal=rainbow
PLT_X_ARROW, PLT_Y_ARROW, ysequence(pressure)
yes? LABEL/nouser `($ppl$xlen)/2`
`($ppl$ylen)+0.5`, 0, 0, 0.12, Colored by wind pressure
(`wind_speed,return=units`)
yes? frame/file=sticks.gif
On 10/28/2013 11:04 AM, Ansley Manke wrote:
Hi Ghansham,
You can certainly open these datasets, and work with the
variables and attributes in the file. We are working on
some tools ourselves to make use of some of these file
types, but there is not yet much in the way of automatic
handling of this data. Watch for new capabilities in
upcoming releases of Ferret.
Ansley
On 10/27/2013 5:53 PM, Ghansham Sangar wrote:
Is it possible to open point
datasets in netcdf format following CF conventions (see
discrete sampling geometry in cf metedata conventions1.6
document available online). I could not find online
documentation regarding same. I am usinfg ferret 6.84.
The dataset is satellite derived wind vectors having
relevant fields (ucomp, vcomp, wind speed, Windows
direction, latitude, longitude, date/time of each
observation).
Ghansham
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