DESCRIPTION  Geodetic Institute, Karlsruhe Institute of Technology, Germany
 OUTPUT       5-min enhanced GPS Integrated Water Vapour product
 CONTACT      Peng Yuan, peng.yuan@kit.edu; Geoffrey Blewitt, gblewitt@unr.edu 
 INPUT        NGL: GPS ZTD; ERA5 pressure level product: pressure and Tm

 NGL: Nevada Geodetic Laboratory, University of Nevada, http://geodesy.unr.edu
 ERA5: the fifth generation ECMWF reanalysis, https://www.ecmwf.int
 Authors:     Peng Yuan, Geoffrey Blewitt, Corné Kreemer, William C. Hammond, 
              Donald Argus, Xungang Yin, Roeland Van Malderen, Michael Mayer,
              Weiping Jiang, Joseph Awange, Hansjoerg Kutterer

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File: NGL2020_12552_blgph.txt
Description: coordinates of the 12552 GPS stations worldwide
Format:
  column #1: Site name
  column #2: Latitude (degree)
  column #3: Longitude (degree)
  column #4: Geopotential altitude (geopotential meter)

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ZIP files: data saved according to the first letter of the station names
Description: enhanced GPS IWV data product at 12552 stations worldwide
Structure:   saved as each day for each station, and then all the daily
             files of each station were saved as respective ZIP file
             which named as "site"_2020.trop.zip
Format: IGS TROP format