ASSESSMENT OF EGNOS TROPOSPHERIC CORRECTION MODEL IN SOUTH EGYPT

Aswan-Faculty of Engineering, South Valley University, EGYPT

Tropospheric delay is the second major source of error after the ionospheric delay for satellite

navigation systems. The transmitted signal could face a delay caused by the troposphere of over

2m at zenith and 20m at lower satellite elevation angles of 10 degrees and below. Positioning

errors of 10m or greater can result from the inaccurate mitigation of the tropospheric delay. Many

techniques are available for tropospheric delay mitigation consisting of surface meteorological

models and global empirical models. Surface meteorological models need surface meteorological

data to give high accuracy mitigation while the global empirical models need not. Different

satellite based augmentation systems use this type of models such as EGNOS model for the

EGNOS augmentation system. This paper presents an assessment study of the behaviour of the

EGNOS model compared with highly accurate IGS-tropospheric estimation for South Egypt

region (Aswan city). The study was assessed for TNML station in China as it has similar latitude

and height with Aswan station for the lake of IGS-trop. Estimates for Aswan station. The study

was performed over four non-consecutive weeks on different seasons over one year. It can be

concluded that the EGNOS tropospheric correction model has shown acceptable level of

accuracy in describing the average tropospheric delay model as it agrees reasonably well with the

IGS-tropospheric estimates based on GPS measurements. The mean difference in total zenith

delay between the EGNOS model and the precise IGS-estimations of the tropospheric delay is

about 3.9 cm with maximum difference of up to 5.8 cm. The root mean square of the difference

in total zenith delay is 6.5 cm.