| |
 |
|
|
Science Forum Index » Geology - Satellite Navigation Forum » NOAA APPLIES GPS DATA TO MONITOR THE GLOBAL TROPOSPHERE
Page 1 of 1
|
| Author |
Message |
| Sam Wormley |
 Posted: Fri Jan 19, 2007 11:17 pm |
|
|
|
Guest
|
January 19, 2007
NOAA APPLIES GPS DATA TO MONITOR THE GLOBAL TROPOSPHERE
For almost two decades, NOAA's National Geodetic Survey has been generating
accurate orbits for Global Positioning System (GPS) satellites by processing
data collected at a global network of ground-based satellite tracking stations.
While this activity has primarily supported precise positioning activities,
it can also provide valuable meteorological information in the vicinity of each
tracking station. For this latter purpose, NOAA is collaborating with about
seven other international GPS-analysis organizations to publish hourly values
for the zenith tropospheric delay (ZTD) at about 200 GPS satellite tracking
stations spanning the Earth. ZTD quantifies the delay in the travel time of
a radio signal, which is due to refraction, as this signal passes through the
troposphere from a GPS satellite to a point on the Earth's surface. ZTD equals
the sum of the delay due to the hydrostatic atmospheric constituents ("dry delay")
and that due to the water vapor in the atmosphere ("wet delay"). Because the
dry delay can be reliably determined from barometric pressure values, the amount
of water vapor situated above the tracking station can be accurately deduced.
Information about water vapor is important to meteorologists because adverse
weather is most often associated with water vapor precipitation. In the near
future, NOAA plans to provide two additional parameters for each tracking station.
These parameters would quantify the horizontal gradient of tropospheric refraction.
That is, they would better quantify the tropospheric delay in other directions
above a point, in addition to the zenith direction. (For more information
contact: Bill.Kass@noaa.gov) |
|
|
| Back to top |
|
| |
|
Page 1 of 1
All times are GMT - 5 Hours
The time now is Thu Jan 08, 2009 3:05 pm
|
|