Global Navigation Satellite System (GNSS) Troposphere Zenith Path Delay (ZPD) product from NASA CDDIS

This derived product set consists of Global Navigation Satellite System Final Troposphere Zenith Path Delay (ZPD) Product (daily files by station) from the NASA Crustal Dynamics Data Information System (CDDIS). GNSS provide autonomous geo-spatial positioning with global coverage. GNSS data sets from ground receivers at the CDDIS consist primarily of the data from the U.S. Global Positioning System (GPS) and the Russian GLObal NAvigation Satellite System (GLONASS). Since 2011, the CDDIS GNSS archive includes data from other GNSS (Europe’s Galileo, China’s Beidou, Japan’s Quasi-Zenith Satellite System/QZSS, the Indian Regional Navigation Satellite System/IRNSS, and worldwide Satellite Based Augmentation Systems/SBASs), which are similar to the U.S. GPS in terms of the satellite constellation, orbits, and signal structure. Analysis Centers (ACs) of the International GNSS Service (IGS) retrieve GNSS data on regular schedules to produce troposphere ZPD estimates for stations of the IGS network. The primary troposphere products generated from ground-based GNSS data are estimates of total zenith path delay and north/east troposphere gradient. Ancillary measurements of surface pressure and temperature allow the extraction of precipitable water vapor from the total zenith path delay. The IGS Troposphere Analysis Center Coordinator (ACC) uses these individual AC solutions to generate the official IGS troposphere ZPD estimates for many of the stations in the IGS network. The final products consist of daily files containing data from each observing station. All ZPD solution files utilize the Solution INdependent EXchange format for combination of TROpospheric estimates (SINEX_TRO) and span 24 hours from 00:00 to 23:45 UTC.