International Global Navigation Satellite Systems Association
IGNSS Conference 2018
Colombo Theatres, Kensington Campus, UNSW Australia
7 – 9 February 2018
Use of GPS Data as Evidence in Court
Andrew Dempster (1)
Australian Centre for Space Engineering Research
School of Electrical Engineering and Telecommunications
UNSW Sydney
+61 2 93856890, a.dempster@unsw.edu.au
ABSTRACT
There has been a proliferation of the use of GNSS logged data in court as
evidence. This paper acts as a short literature survey on the topic, looking
particularly at the quality of that data. It does not present new results; rather
it identifies areas where research can be developed that results in reliable
evidence in court.
KEYWORDS: GPS, GNSS, Data reporting, Court evidence.
1. INTRODUCTION
Satellite navigation data is increasingly being presented in court to support prosecution and
defence of both civil and criminal cases. The range of applications being examined is wide;
the range of questions that the Global Navigation Satellite Systems (GNSS) receiver is
required to answer is also wider than may appear obvious. Despite this wide-ranging use of
GNSS, there are surprisingly few contributions to the research literature on GNSS data used
as evidence.
In the early days of the Global Positioning System (GPS), especially when space-based
augmentation systems (SBAS) were being developed, the main legal concern regarding GPS
was liability for “error”, where the word error could be considered to have a binary value –
either an error was made or it was not [1]. GPS and the open Galileo signals were considered
unlikely to attract liability but SBAS and the Galileo commercial and safety of life signals
were more likely because they were committed to a level of service [2]. It was found that
“Space Law treaties cannot solve liability questions about the failure of a GNSS signal” [3].
Efforts by ICAO to develop an international treaty or convention on GNSS liability have not
yet borne fruit [4]. The greater exposure of the Galileo commercial and safety of life signals
to liability was marketed during system development as an advantage over GPS [5], giving a
stick for the Europeans to beat the Americans with, as Selective Availability (SA) was still
operating (i.e. Galileo was a civilian system, with guaranteed accuracy, for which they would
take responsibility, whereas GPS was a system the US military could arbitrarily degrade to
