Session 3: Using OPeNDAP-enabled Applications to Access Australian Data Services and Repositories eResearch Australasia 2011, ½ Day Morning Workshop, Thursday.

Session 3: Using OPeNDAP-enabled Applications to Access Australian Data Services and RepositorieseResearch Australasia 2011, ½ Day Morning Workshop, Thursday 10th November 2011

GENERAL INFORMATION

• This is a half-day workshop (9am to 12:30pm)

• 9:00am Introductions and Participants Goals

• 9:15am Session 1: Discovering OPeNDAP data access services

• 10:00am Session 2: Applicable use cases of OPeNDAP data services

− 10:30am Tea Break for 15 minutes

• 11:00am Session 3: OPeNDAP service protocols and features

• 11:45am Session 4: Accessing complementary features and services

• 12:30pm End of Workshop

11:00am Session 3: OPeNDAP service protocols and features 11:00am Session 3: OPeNDAP service protocols and features

Session 3

• OPeNDAP service protocols and features to support meta-data discovery and efficient data access and extraction.

• A short tutorial on meta-data and data access and extraction using an OPeNDAP-enable client application.

• 45 minutes in length

MATLAB

MATLAB® is commercial software, that is a high-level technical computing language and interactive environment for algorithm development, data visualization, data analysis, and numerical computation

To support OPeNDAP remote data access, do the following:1. Get a matlab-macos.zip or matlab-windows.zip from Tim2. Install in users home directory and unzip3. Modify the startup.m paths to suit each user4. Startup MATLAB and check whether the startup.m file was read,

and the paths are correct.

MATLAB demo

>> addpath /usr/local/bin

>> url = 'http://test.opendap.org/opendap/hyrax/netcdf/examples/ECMWF_ERA-40_subset.nc’

>> ce='time’

>> loaddap('-V')

loaddap: 3.7.0

>> loaddap([url '?' ce])

… the vector ‘time’ is loaded into the workspace

>> ce1=’lsp’

>> loaddap([url '?' ce1])

Creating matrix lsp (62 x 73 x 144) with 651744 elements.

Creating vector time with 62 elements.

Creating vector latitude with 73 elements.

Creating vector longitude with 144 elements.

>> addpath /usr/local/bin

>> url = 'http://test.opendap.org/opendap/hyrax/netcdf/examples/ECMWF_ERA-40_subset.nc’

>> ce='time’

>> loaddap('-V')

loaddap: 3.7.0

>> loaddap([url '?' ce])

… the vector ‘time’ is loaded into the workspace

>> ce1=’lsp’

>> loaddap([url '?' ce1])

Creating matrix lsp (62 x 73 x 144) with 651744 elements.

Creating vector time with 62 elements.

Creating vector latitude with 73 elements.

Creating vector longitude with 144 elements.

MATLAB demo, cont

>> ce2='lsp[61][0:72][0:143]’

>> loaddap([url '?' ce2])

Creating matrix lsp (1 x 73 x 144) with 10512 elements.

Creating vector time with 1 elements.

Creating vector latitude with 73 elements.

Creating vector longitude with 144 elements.

>> ce3='grid(lsp,"time=899202")’

>> loaddap([url '?' ce3])

Creating matrix lsp (1 x 73 x 144) with 10512 elements.

Creating vector time with 1 elements.

Creating vector latitude with 73 elements.

Creating vector longitude with 144 elements.

>> ce2='lsp[61][0:72][0:143]’

>> loaddap([url '?' ce2])

Creating matrix lsp (1 x 73 x 144) with 10512 elements.

Creating vector time with 1 elements.

Creating vector latitude with 73 elements.

Creating vector longitude with 144 elements.

>> ce3='grid(lsp,"time=899202")’

>> loaddap([url '?' ce3])

Creating matrix lsp (1 x 73 x 144) with 10512 elements.

Creating vector time with 1 elements.

Creating vector latitude with 73 elements.

Creating vector longitude with 144 elements.

MATLAB and SNCtools demo

% ex_snctools_opendap.m

% Read from a remote OPeNDAP server with the same file

%

ncRef = 'http://opendap.bom.gov.au:8080/thredds/dodsC/gamssa_4deg/2011/20111106-ABOM-L4LRfnd-GLOB-v01-fv01.nc'

nc_dump( ncRef );

pause

temp = nc_varget( ncRef, 'analysed_sst');

lon = nc_varget( ncRef, 'lon');

lat = nc_varget( ncRef, 'lat');

imagesc(lat, lon, temp); axis xy

% ex_snctools_opendap.m

% Read from a remote OPeNDAP server with the same file

%

ncRef = 'http://opendap.bom.gov.au:8080/thredds/dodsC/gamssa_4deg/2011/20111106-ABOM-L4LRfnd-GLOB-v01-fv01.nc'

nc_dump( ncRef );

pause

temp = nc_varget( ncRef, 'analysed_sst');

lon = nc_varget( ncRef, 'lon');

lat = nc_varget( ncRef, 'lat');

imagesc(lat, lon, temp); axis xy

MATLAB and NJTbx demo

% ex_njtbx.m

% Read from a remote OPeNDAP server with the same file

%

ncRef = 'http://opendap.bom.gov.au:8080/thredds/dodsC/gamssa_4deg/2011/20111106-ABOM-L4LRfnd-GLOB-v01-fv01.nc'

nj_info( ncRef )

pause

[temp, grid] = nj_grid_varget(ncRef,'analysed_sst');

imagesc(grid.lon, grid.lat, temp); axis xy; colorbar

% ex_njtbx.m

% Read from a remote OPeNDAP server with the same file

%

ncRef = 'http://opendap.bom.gov.au:8080/thredds/dodsC/gamssa_4deg/2011/20111106-ABOM-L4LRfnd-GLOB-v01-fv01.nc'

nj_info( ncRef )

pause

[temp, grid] = nj_grid_varget(ncRef,'analysed_sst');

imagesc(grid.lon, grid.lat, temp); axis xy; colorbar

Panoply

Panoply is a cross-platform application which plots geo-gridded arrays from netCDF, HDF and GRIB datasets.

To install Panoply on Windows, go to http://www.giss.nasa.gov/tools/panoply/download_win.html

To install Panoply on Mac OS X, go to http://www.giss.nasa.gov/tools/panoply/download_mac.html

To install Panoply on Linux and other systems, go to http://www.giss.nasa.gov/tools/panoply/download_gen.html

Panoply demo

1. Load the catalog and navigate it to the data set of interest

2. Select a data set and view the metadata

3. Graph some data

4. Select velocity data and plot vectors

Tutorial: Pick a demo to try

Please select from MATLAB or Panoply demos1. Install the software on your machine2. Run a test case and see if the software is installed correctly3. Access a different file from a TDS or Hyrax data service4. Get the metadata information5. Access some data and graph it

Thank you

Authors:

Tim F. Pugh1, James Gallagher2, Dave Fulker3

1Australian Bureau of Meteorology, Melbourne, Australia, [email protected] OPeNDAP, Butte, Montana, USA, [email protected] OPeNDAP, Boulder, Colorado, USA, [email protected]