TITLE:
Satellite Clock Error and Orbital Solution Error Estimation for Precise Navigation Applications
AUTHORS:
Bharati Bidikar, Gottapu Sasibhushana Rao, Laveti Ganesh, MNVS Santosh Kumar
KEYWORDS:
Satellite Clock Error; Satellite Clock Offset; Orbital Solution; Broadcast Ephemerides
JOURNAL NAME:
Positioning,
Vol.5 No.1,
February
13,
2014
ABSTRACT:
Global Positioning System (GPS) is a satellite-based navigation system that provides a three-dimensional user position (x,y,z), velocity and
time anywhere on or above the earth surface. The satellite-based position accuracy is affected by several factors such as satellite clock error, propagation path
delays and receiver noise due to which the GPS does not meet the requirements
of critical navigation applications such as missile navigation and category
I/II/III aircraft landings. This paper
emphasizes on modelling the satellite clock error and orbital solution (satellite position) error considering the
signal emission time. The transmission time sent by each satellite in broadcast
ephemerides is not accurate. This has to be corrected in order to obtain
correct satellite position and in turn a precise
receiver position. Signal transmission time or broadcast time from satellite
antenna phase center is
computed at the receiver using several parameters such as signal reception
time, propagation time, pseudorange
observed and satellite clock error correction parameters. This corrected time
of transmission and broadcast orbital parameters are used for estimation of the
orbital solution. The estimated orbital solution was validated with the precise ephemerides which are
estimated by Jet Propulsion Laboratory (JPL), USA. The errors are estimated for a typical day data
collected on 11th March 2011 from dual frequency GPS receiver
located at Department of Electronics and Communication Engineering, Andhra
University College of Engineering, Visakhapatnam (17.73°N/83.319°E).