Introduction by Attila Komjathy
-------------------------------
Colleagues,

In the corresponding directories below you will find the 
JPL GPS-derived TEC data in the *.dump files. Please find below the 
description of the individual columns. We also generated VTEC movies 
using this dump files below. If you have any questions please feel 
free to contact me at <komjathy@jpl.nasa.gov>.
Look forward to hearing from you.

Best wishes,

Attila Komjathy

Main README by Tony Mannucci
----------------------------
Do not hesitate to contact me: tony.mannucci@jpl.nasa.gov

Much of the information below applies to the November 20, 2003 data
set, although other data sets have similar features, however, they may
not be so complete. Feel free to contact me about the availability of
other days.

The *.dump files may be in compressed format (.Z). This is the UNIX
"compress" program. The files can be uncompressed on a UNIX box using
uncompress, or one can use a utility for your operating system.  This
is a widely recognized compression scheme, so uncompressors can be
found readily. These are text files with UNIX line endings.

MOVIE FILES
-----------
mpeg format movies are in the corresponding directories,
with file names similar to allsitesYMMDD.mpeg. More specifically:

"allsites" -- many sites from the GPS global network "cors_conus" --
the CORS network over the US ***BRAND NEW*** "diff" -- a difference
map, showing features associated with the storm day of interest. The
difference is taken between the day of interest and approximately the
mean of five quiet days just prior to or after the storm day.  NOTE:
this is an experimental product, but we believe it will turn out to be
very useful. Your feedback is welcome.

NOTE about mpeg movies:
The information content of the mpegs depends strongly on the 
color scale used. The community should provide a mechanism for 
replotting mpegs. We could upload the raw grid files used to generate
them if there is sufficient interest.

Station Locations 
----------------- 
Station locations can be found in the file coord.all.stlocs for days
it is provided (e.g. Nov 20, 2003).

Format: stnid  latitude longitude height (m)

latitude and longitude are geographic degrees.

REMARK ABOUT DATA SETS AND DATE:
--------------------------------
Currently, the November 20 2003 data set is by far the most
complete. The same information does not yet exist for other days
listed here. We are working towards complete data sets for other
storms.  Please let us know what you need.

J2000 reference times (see the space_data readme for more info):
Nov 20, 2003: 122558400.0 (seconds past "J2000": 1200UT, Jan 1 2000)

IMPORTANT NOTE:
---------------
Use the "lowrate" data for most TEC studies...

To meet the needs of studies that examine rapid TEC fluctuations
associated with ionospheric irregularities, some of these data sets
were generated using "loose" editing criteria that may have left cycle
slips in the data.  Therefore, users of these data should apply
additional quality control and data editing criteria before reaching
scientific conclusions. We at JPL would be happy to work with data
users on this point.

The data in the subdirectory "lowrate" is "tightly" edited 5-minute
data. The data in the "highrate" subdirectory is loosely edited data
at a 30-second cadence. BEWARE that these data files are much larger
than the 5-minute files.

TEC file format
---------------
TEC dump file format:
       Data Format:

        time (seconds past J2000, GPS time)
        receiver name
        transmitter name
        azimuth (degrees)
        elevation (degrees)
        IPP latitude, in Earth-fixed degrees
        IPP longitude, Earth-fixed
        IPP longitude, Sun-fixed
        reference station name
        Angular distance between IPP and reference station zenith
point(degrees) -- ignore
        Linear distance at ionospheric shell height -- ignore
        Hour in the day (UTC time)
        Human-readable date-time (GPS time)
        Slant tec, unbiased, TECU
        Vertical TEC, unbiased, TECU, using fixed obliquity function
        GIM delay (TECU, if applicable)
        Difference between GIM and measured vertical TEC (stec_diff, if
applicable)
        Data noise (estimate, not validated)
        Obliquity ratio for this measurement
        Satellite bias value (TECU)
        Receiver bias value (TECU)
        IPP latitude, Solar-magnetic coordinates
        IPP longitude, Solar-magnetic coordinates
        Receiver X Coordinate, relative to geocenter (km)
        Receiver Y Coordinate (km)
        Receiver Z Coordinate (km)
        Transmitter X Coordinate (km)
        Transmitter Y Coordinate (km)
        Transmitter Z Coordinate (km)
        UTC Time (sec)
        UTC Date/Time
        Obs Slant TEC from Pseudorange (TECU)