How to Visualize HDF-EOS data Using Ferret OPeNDAP
Ferret
is a visualization and analysis tool for gridded
and non-gridded data. The
OPeNDAP
protocol allows users to access
data anywhere from the internet using a variety of client/server methods,
including Ferret.
Installing Ferret
Users can download Ferret from
here
.
Recent binary distributions exist for RedHat Linux. Windows users are
recommended to run the Linux executable under the (free) Virtual Box
virtualization environment. See the
WINDOWS README
file for more details.
We will examine an
HDF4
data file from the NASA Goddard Earth
Sciences Data and Information Services Center
(GESDISC)
.
Ferret can retrieve the attributes and fields of the data file via the
OPeNDAP interface using the
show data command.
Ferret responds as follows.
Figure 3 Ferret show data response
currently SET data sets:
1> https://eosdap.hdfgroup.org:8080/opendap/data/NASAFILES/hdf4/3B43.070901.6A.HDF(default)
name title I J K L
PRECIPITATION_DATA_GRANULE_PLANETARYGRID
precipitation1:14401:400 1:1 ...
RELATIVEERROR_DATA_GRANULE_PLANETARYGRID
relativeError1:14401:400 1:1 ...
The
SHOW DATA command verifies that this is indeed a remote
dataset.
Next we will examine an
HDF5
data file from NASA
GESDISC
.
Figure 4 Connect to the remote HDF5 data file via OPeNDAP in Ferret
yes? USE "https://eosdap.hdfgroup.org:8080/opendap/data/NASAFILES/hdf5/OMI-Aura_L3-OMTO3e_2005m1214_v002-2006m0929t143855.he5"
yes? show data
currently SET data sets:
1> https://eosdap.hdfgroup.org:8080/opendap/data/NASAFILES/hdf5/OMI-Aura_L3-OMTO3e_2005m1214_v002-2006m0929t143855.he5
(default)
name
title
I J K L
COLUMNAMOUNTO3
1:14401:720 ... ...
REFLECTIVITY331
1:14401:720 ... ...
UVAEROSOLINDEX
1:14401:720
...
...
Generate a FILLED plot of the COLUMNAMOUNTO3 data field
Draw the coastlines onto the map using the
land script.
Next we will examine an HDF-EOS2 grid file from NASA
Land Processes Distributed Active Archive Center
(LPDAAC).
Figure 8 Access HDF-EOS2 data file via OPeNDAP in Ferret
yes? USE "https://eosdap.hdfgroup.org:8080/opendap/data/NASAFILES/hdf4/MYD11C2.A2006337.004.2006348062459.hdf"
yes? show data
currently SET data sets:
1> https://eosdap.hdfgroup.org:8080/opendap/data/NASAFILES/hdf4/MYD11C2.A2006337.004.2006348062459.hdf(default)
name title I J K L
...
LST_NIGHT_CMG
8-day nighttime 3min CMG Land-s1:72001:3600... ...
...
We have omitted 15 data fields from the output report.
We generate a FILLED plot of the LST_NIGHT_CMG data field.
The dataset size is big.
Thus, you may want to increase the memory to 512M with set MEMORY/SIZE=512 command
if you encounter a memory error during fill command execution.
Last modified: 06/02/2017
