GNSS Atmospheric Products

Other IGS products, such as troposphere and ionosphere products, have been developed through working group or pilot project activities and are stored using separate directory structures within the GNSS products area of the archive. These products include troposphere ZPD estimates, along with statistics about the product, derived from GNSS measurements and ionosphere vertical total electron content maps for climate research and atmospheric studies.

Troposphere

IGS associate analysis centers generate troposphere products from ground-based GNSS data. These products include five-minute estimates of zenith path delay (ZPD) and north and east troposphere gradient components. Data are available in daily files by site for over 350 GNSS stations in the IGS network. Measurements of surface pressure and temperature at GNSS sites allow the extraction of precipitable water vapor from the total zenith path delay. Final troposphere estimates for over 350 stations in the IGS network. The troposphere products utilize the IGS final satellite, orbit, and EOP products and are therefore available approximately three weeks following the observation day. Troposphere products are available in a standard, IGS format.

Since the inception of the troposphere product, three analysis groups (GFZ, JPL, and currently USNO) have generated the IGS combination solution each using different methodologies. Therefore, the resulting file types have changed through the years. The current product consists of files containing daily ZPD estimates for selected sites in the IGS network. The original product consisted of one file per site per GPS week.

Historical tropospheric producst are also available. These products are no longer updated.

The starting directory for the current troposphere solution files is:

ftp://cddis.gsfc.nasa.gov/gnss/products/troposphere/zpd/

Append the following directory and file names to the starting directory for current files:

TYP/SSSSDDD#.YYzpd.gz

as described in the table below.

Code Meaning
TYP type of solution (zpd or sub, analysis center input products to combined zpd product)
SSSSIGS monument name
DDD3-digit day of year
#file number for the day, typically 0
YY2-digit year
.gz gzip compressed file

The starting directories for the historical troposphere product files are:

Starting DirectoryProducts
ftp://cddis.gsfc.nasa.gov/gnss/products/troposphere/cmp/Comparison results between initial IGS troposphere product (generated by GFZ) and JPL solution (through 2009)
ftp://cddis.gsfc.nasa.gov/gnss/products/troposphere/old/Earlier versions of IGS troposphere products, produced by GFZ
ftp://cddis.gsfc.nasa.gov/gnss/products/troposphere/rpt/Product reports by GPS week, produced by JPL (through 2009)
ftp://cddis.gsfc.nasa.gov/gnss/products/troposphere/sta/Reports and supporting information on station troposphere products, produced by JPL (through 2009)

Ionosphere

Since 1998, IGS associate analysis centers have provided products containing ionosphere vertical total electron content (TEC) maps and daily GPS satellite differential code bias (DCB) values derived from the dual-frequency GPS data. Daily ionospheric fluctuation maps are also available. The IGS product is derived from analysis center solutions, both rapid and final. These ionosphere products are available in a rapid solutions with a latency of less than 24 hours, a final solution with a latency of approximately 11 days, and a predicted solution, available both one and two days prior. Ionosphere products are provided in IONEX (ionosphere exchange) format.

The starting directory for the current ionospheric solution files is:

ftp://cddis.gsfc.nasa.gov/gnss/products/ionex/

Append the following directory and file names to the starting directory for current files:

YYYY/DDD/AAAgDDD#.YYi.Z

Vertical total electron content (TEC) maps


YYYY/DDD/rotiDDD0.YYf.Z

Daily ROTI (rate of TEC index) product


as described in the table below.

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CodeMeaning
c1p1-day predicted solution (CODE)
c2p2-day predicted solution (CODE)
codFinal solution (CODE)
corRapid solution (CODE)
e1p1-day predicted solution (ESA)
e2p2-day predicted solution (ESA)
ehrRapid high-rate solution, one map per hour, (ESA)
esaFinal solution (ESA)
esrRapid solution (ESA)
ilp1-day predicted solution (IGS combined)
i2p2-day predicted solution (IGS combined)
igrRapid solution (IGS combined)
igsFinal combined solution (IGS combined)
jplFinal solution (JPL)
u2p2 day predicted solution (UPC)
upcFinal solution (UPC)
uhrRapid high-rate solution, one map per hour, (UPC)
uprRapid solution (UPC)
uqrRapid high-rate solution, one map per 15 minutes, (UPC)
Code Meaning
YYYY 4-digit year
DDD3-digit day of year
AAAAnalysis center name
#file number for the day, typically 0
YY2-digit year
.Z Unix compressed file

The IGS analysis centers re-processed the historical IGS data set (from 1994 to 2007 for repro1, from 1994 through 2012/2013 for repro2) to produce a fully consistent set of products utilizing the most recent models and updated processing strategies.