Re: [ferret_users] netcdf point datasets in ferret

[Ansley Manke <ansley.b.manke@xxxxxxxx>]

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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Attachment: arrows.gif
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