International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 2
Number 3
September 2008
235
An Effect of Urban Development on the
Accuracy of the GPS/EGNOS System
R. Bober, T. Szewczuk & A. Wolski
Maritime University of Szczecin, Szczecin, Poland
ABSTRACT: This article presents the results of research into the accuracy of position determination by a
GPS/EGNOS system in a densely built-up residential area. These results are compared with the relevant
results obtained for a position in an open area.
1 INTRODUCTION
The EGNOS system makes up a superimposition for
the GPS and GLONASS systems which allows to
enhance the accuracy, availability, reliability and
continuity of position determination.
The accuracy of position determination in the
GPS/EGNOSS system is about 3-5 m (p=0.95) and
depends on a number of factors. The number and
configuration of observable satellites is one of the
factors significantly affecting the accuracy. These
depend on the position of the antenna and its
environment. The antenna location has an influence
on the number of tracked satellites, while the
environment may cause the effect of multitracking.
This article attempts at assessing the accuracy of
position determination by a GPS/EGNOS system in
an urban densely built up area and at comparing it
with positions obtained in an open area.
2 RESEARCH AREA
Three characteristic measurement locations were
chosen within Szczecin area (Fig. 1) for the
assessment of position determination accuracy
obtained with the use of a GPS/EGNOS system:
− measuring point Glinki(A), located in an open
area without buildings, with grassy ground,
offering good conditions of signal reception;
− measuring point ul. Bolesława Śmiałego(B),
located in a narrow street with rows of adjacent
buildings about 25 metres high. The antenna was
installed on a car roof (at height of 2 metres): the
celestial sphere was considerably covered by
buildings, so reflections from walls could be
expected;
− measuring point AM Szczecin(C), located on an
antenna platform, about 35 metres above the
ground, overlooking the roofs of neighbouring
buildings; the antenna could see the whole
celestial sphere, although there were chances for
reflections from neighbouring roofs and slight
shades from radio antennas at a distance of 2 to 4
metres.