Parameterization of atmospheric delay Given the sensitivity of GPS position estimates to atmospheric delay, and that external calibration of the delay is only good to a few centimeters; atmospheric zenith delays and often gradients are estimated high precision GPS analyses Parameterization is either Kalman filter or coefficients of piece-wise linear functions(GAMIT) for comparison of GPS estimates with calculations for global forecast models(NCEP) 0409/03 12540Lec15 Example using NCEP analysis field z0208z0210z02.12 00220 Blue is GPs estimates of delay, red is NCEP calculation 04o903 12540Lec1504/09/03 12.540 Lec 15 23 Parameterization of atmospheric delay • Given the sensitivity of GPS position estimates to atmospheric delay, and that external calibration of the delay is only good to a few centimeters; atmospheric precision GPS analyses. • Parameterization is either Kalman filter or coefficients of piece-wise linear functions (GAMIT) • See: http://www-gpsg.mit.edu/~katyq/plots_gpsdelay/ for comparison of GPS estimates with calculations for global forecast models (NCEP) 04/09/03 12.540 Lec 15 24 Example using NCEP analysis field Blue is GPS estimates of delay, red is NCEP calculation zenith delays and often gradients are estimated high- 12