International Global Navigation Satellite Systems Association
IGNSS Symposium 2018
Colombo Theatres, Kensington Campus, UNSW Australia
7 – 9 February 2018
Integrity Capability of Standalone GPS
Elizabeth Smith
UNSW/DST Group/Australia
(08) 7389 6438 liz.smith@dst.defence.gov.au
Mark Knight
DST Group/Australia
(08) 7389 6864 mark.knight@dst.defence.gov.au
Andrew Dempster
UNSW/Australia
(02) 9385 6890 a.dempster@unsw.edu.au
Joon Wayn Cheong
UNSW/Australia
(02) 9385 6702 cjwayn@unsw.edu.au
ABSTRACT
A vehicle was driven around a rural environment in Albert Park, Victoria
and an urban environment in Melbourne CBD. The GPS receiver data was
collected and processed to determine the position of the vehicle and its
associated position errors and Horizontal Protection Levels (HPL). It was
found that the HPL calculated for the CBD serials did not accurately reflect
the calculated position error of the vehicle, unlike the Albert Park data
which showed consistency between predicted and measured errors. The
cause of the inconsistencies in the CBD data is postulated to be due to
multipath signals contaminating the data, which is supported through
simulation. The faulty satellite pseudoranges were removed using a Fault
Detection and Exclusion process to improve the calculated and reported
errors. The conclusion of this paper is that GPS alone is not capable of
providing accurate position error estimations within urban environments and
is limited in its integrity monitoring capability due to a lack of visible
satellites.
KEYWORDS: Cooperative Intelligent Transport Systems(CITS), GPS,
Horizontal Protection Level (HPL), Integrity, Receiver Autonomous
Integrity Monitoring (RAIM)
