Title: Performance Analysis of a Single-Frequency, Low-Cost GPS Surveying System
Abstract: Over the last decade (or carrier phase-based)
technology has undergone tremendous improvement
and can now routinely deliver centimetre accuracy, though
a not inconsiderable cost. Each receiver typically
costs between US$10,000 and $25,000. Furthermore, two
of them are needed to perform baseline surveys. Top-of-the-
line RTK (real-time-kinematic) systems are even
more expensive. Must there always be a high price to pay
for high performance survey technology? Single-frequency
GPS receiver boards are now available that
cost significantly less than US$1,000. (Dual-frequency
GPS receiver boards are significantly more expensive,
around US$10,000 each, and are therefore not considered
here.) Baseline processing software is also now available
less than US$5,000 a licence. However, real gains in
efficiency, and hence significant reductions in operating
costs, will require the development of new operational pro-cedures.
One strategy is to use data from reference
stations operated by government agencies or private com-panies.
The user need only purchase one unit, and the
requirement for user ownership and operation of a refer-ence
station receiver is removed. A serious impediment in
many countries is therefore the lack of a public refer-ence
station network at sufficient density to support sur-veyors.
The GPS traversing technique developed by the
authors a few years ago overcomes such a constraint and a
reference receiver located many tens of kilometres away
can be used.
In this paper, a carrier phase-based positioning system
based on a low-cost hardware configuration is described.
Several innovative data processing algorithms have re-cently
been developed, such as the aforementioned GPS
traverse mode, and these have been incorpo-rated
within the system design. Testing of the three main
functional positioning modes has commenced: (1) Rapid
static positioning, (2)GPS kinematic positioning, and (3)
the traverse surveying mode.
Preliminary results indicate that the occupation time for
each baseline in the rapid static positioning mode, to ensure quick ambiguity resolution, is of the order of 10 min-utes,
although it varies for different antenna environments.
GPS kinematic positioning with centimetre accuracy using
on-the-fly ambiguity resolution is not reliable enough,
though the system is capable of delivering 1 to 2 decimetre
accuracy. (Kinematic positioning after initial static ambi-guity
resolution is, however, accurate to the few centimetre
level.) The GPS traverse mode is a very at-tractive
technique for surveying across areas where lock on
the satellite signals can be easily maintained, and
hence is a feasible alternative to the stop & go technique.
It can then be used for rapid static positioning (with very
short observation periods of 1-2 minutes) and for kinematic
positioning with centimetre accuracy.
A low-cost surveying system such as this can be used
for a variety of applications, including low order geodetic
control surveys, detail surveys, profile and engineering
surveys, large-scale mapping, cadastral surveys, and so on.
However, new base station-user receiver configurations
that do not mimic current state-of-the-art surveying
systems may have to be developed in order to truly unlock
the potential of such a no-frills system as is proposed
here. One promising option is to use a multi-reference sta-tion
network. A network of 3 or 4 reference receivers
could service an entire metropolitan area. Accuracy and
speed of survey using low-cost receivers could be
considerably enhanced, and new services such as Internet-based
data processing introduced.
Publication Year: 1998
Publication Date: 1998-09-18
Language: en
Type: article
Access and Citation
Cited By Count: 9
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