Ground-based GPS receivers measure the Zenith Total Delay (ZTD) in mm which is the sum of the Zenith Hydrostatic Delay (ZHD) caused by the atmospheres dry components and the Zenith Wet Delay (ZWD) resulting mainly from atmospheric water vapor.
ZTD = ZHD + ZWD
Knowing the atmospheric pressure ZWD can be derived and in a second step converted to the Integrated Water Vapor (IWV).
|Name||Code||PI||Location||Temp. Reso.||No. stations||Products||Data/Day||Availability|
|GFZ GPS Standard net||gps_gfzn||Dick||Central Europe||15 min||∼200||ZTD, ZWD, IWV||∼100 KB||check|
|GPS Standard Switzerland||gps_swit||Brocard||Switzerland||1 h||∼30||ZTD, ZWD, IWV||∼80 KB||check|
— Susanne Crewell 2007/03/25 12:04