Product types
Several STEC/VTEC products are available on our server:
- Daily raw STEC data, sampled every 30 seconds.
- Daily VTEC maps:
- VTEC data interpolated on a regular grid and sampled every 30 seconds.
- VTEC data interpolated on a regular grid and filtered by a 15 minute low pass filter.
- VTEC data interpolated on a regular grid and filtered by a 1 hour low pass filter.
The map extensions are:
- 15° West to 40° East by steps of 2.5°.
- 30° North to 70° North by steps of 2.5°.
Nomenclature
The general product nomenclature is:
AB_YYYY_MM_DD.cdf
The meanings of the fields are:
| A |
Type of the product:
T: raw product (STEC)
M: map product (VTEC)
|
| B |
Time sampling of the product:
H: 1 hour
V: 15 minutes
L: 30 seconds
S: 1 second (only available on demand for specific studies) |
| YYYY |
Year of the GPS data used for the product creation
|
| MM |
Month of the GPS data used for the product creation
|
| DD |
Day of the GPS data used for the product creation
|
Formats
Products are delivered in the netCDF format (platform independent format).
The netCDF format is recognized by many scientific software and is also easily read by users' programs calling the netCDF library (see the Unidata web site for details).
The product formats are described hereafter.
Raw products
- List of the satellite identifiers observed during the day.
- Names of the station that have received GPS signals during the day.
- Positions (longitude, latitude, and altitude) of the stations (assumed fixed during the day).
- For every GPS measurement:
- Instant of the observation (hh:mm:ss).
- Position (x, y, and z in WGS 84) of the observed satellite.
- Satellite identifier.
- TGD of the satellite (TEC unit).
- Uncertainty on the TGD of the satellite (TEC unit).
- Name of the station receiving the GPS signal.
- IFB (TEC unit) of the station compared to the station taken as reference (IFB=0).
- Uncertainty on the IFB of the station (TEC unit).
- Longitude of the SIP (degrees).
- Latitude of the SIP (degrees).
- Estimated STEC at the SIP (TEC unit), including the biases (IFB and TGD).
- Obliquity factor between the satellite and the station.
A detailed description of the raw product format can be found here.
Note that VTEC data at the SIP can be obtained using the formula:
VTEC = ( STEC - TGD - IFB ) * Obliquity
VTEC maps
- Date of each VTEC map.
- Longitude of the grid points (degrees).
- Latitude of the grid points (degrees).
- List of the satellite identifiers.
- List of the station names.
- Matrix of the observation pairs between satellites and stations.
- Interpolated VTEC at the grid points (TEC unit).
- Uncertainty on the interpolated VTEC (TEC unit).
A detailed description of the VTEC map format can be found here.
Filtered VTEC maps
- Date of each original VTEC map (hh:mm:ss).
- Date of each filtered VTEC map (hh:mm:ss).
- Longitude of the grid points (degrees).
- Latitude of the grid points (degrees).
- List of the satellite identifiers.
- List of the station names.
- Matrix of the observation pairs between satellites and stations.
- Interpolated VTEC at the grid points (TEC unit).
- Uncertainty on the interpolated VTEC (TEC unit).
Detailed descriptions of the filtered VTEC maps can be seen here (15 minute filtered map) and there (1 hour filtered map).
Data volume
Below are reported typical product sizes.
| Product |
Original size
(MBytes) |
Gzipped
(MBytes) |
| Raw |
300 |
150 |
| Map |
46 |
10 |
| 15 minute map |
38 |
1.6 |
| 1 hour map |
37 |
1.4 |