This version of LinkWinds is the last planned release. Our work
continues with a similar package, written in Java, called WebWinds
(http://webwinds.jpl.nasa.gov).
This release fixes several bugs and adds a database interface to the list
of compatible formats. Due to a lack of available hardware, the IBM version has
not been updated.
BUG FIXES:
Previous versions of LinkWinds would crash when they encountered arrays
with more than 4 dimensions. Although this version still can only handle
4 or fewer dimensions, errors are handled more gracefully. Dimensions beyond
4 are ignored.
LIBRARY UPDATE:
LinkWinds Version 2.3 uses NCSA's Hierarchical Data Format (HDF)
version 4.1, release 1 (1). Note: HDF 4.1 release 1 had a bug in its
NetCDF interface. LinkWinds 2.3 executables include a patch from NCSA
that fixes this bug.
DATABASE INTERFACE:
The addition to the database interface in 2.3 is the last
format in the list below, namely HDF-EOS.
The formats accepted by LinkWinds 2.3 are:
- Raw binary data in signed and unsigned 1, 2 and 4 byte integers and 4 and 8 byte floating point.
- The Common Data Format (CDF).
- NetCDF.
- The Silicon Graphics, Inc. native RGB image format.
- Data with Planetary Data System (PDS) headers.
- The astrophysics Flexible Image Transport System (FITS).
- ASCII text data.
- Two data formats of UARS, the Upper Atmosphere Research Satellite. Both the format maintained by the Goddard DAAC and the UNIX variant of the format of the Central Data Handling Facility (CDHF) are readable.
- The Stratospheric Aerosol and Gas Experiment (SAGE) data format.
- HDF-EOS including NASA Scatterometer data.
HDF-EOS is an particular application of HDF developed for NASA's Earth
Observing System (EOS). It is a schema built from basic HDF data
elements. LinkWinds currently uses version 2.00 of the HDF-EOS
programming interface. We give a very brief description here of the
data structures defined in HDF-EOS. For a little more detail, see
Volume 1 of the HDF-EOS User's Guide. It's available from the
following web sites:
http://ulabhp.gsfc.nasa.gov/~workshop/hdf.html
http://ecsinfo.hitc.com/iteams/HDF-EOS/HDF-EOS.html
HDF-EOS was designed to store data from a wide variety of instruments,
aboard Earth-orbiting satellites, plus other data sources. The three
basic structures are known as Grids, Swaths, and Points.
Grids are rectilinear arrays. The data have been converted from their
original sources into physically meaningful quantities. In remote
sensing parlance, these are referred to as "processing level 3" and
above. LinkWinds reads Grid data through the vanilla SD interface.
Swaths were designed specifically to handle data from satellites and
aircraft. A swath is typically thought of as all the data from a
single orbit. However, the swath data structure may hold any number
of orbits or fractions of an orbit. So-called "level 2" data are
georeferenced, and sometimes expressed in physically meaningful units.
Other, less processed data, known as level 1b, are not georeferenced,
and contain only time and signal strength and quality information.
When it can, LinkWinds will match data to geographic coordinates and
rebin the data onto a latitude-longitude grid. Otherwise, the data
will be rendered in their original dimensions.
Points are linked tables of loosely structured data. The most common
application would probably be to hold data from ground stations or
balloons. Unlike remotely-sensed data, these would normally be direct
measurements of physical quantities, such as temperature, soil type,
downward radiation, and sea-level height. As of this writing, we are
unaware of any real examples of point structures,
and the format is not supported in LinkWinds.
NSCAT:
Some code has been included to read NASA Scatterometer data from
the JPL Physical Oceanography Distributed Active Archive Center
(PO-DAAC). These functions were merely an attempt to understand
orbital swath data, and were written before the LinkWinds Team had
access to actual HDF-EOS samples. The functions have not been
fully tested, so you may encounter limitations if you try
to do something very sophisticated with such data, such as
concatenation of files.
NOTE:
File concatenation is not supported for HDF-EOS datasets.
