Journal of Global Positioning Systems (2004)
Vol. 3, No. 1-2: 280-289
GNSS for sports – sailing and rowing perspectives
K.Zhang, R. Deakin, R. Grenfell, Y. Li, J. Zhang, W.N. Cameron, D.M. Si lcock
School of Mathematical and Geospatial Sciences, RMIT Univer sity, Melbourne, Australia
e-mail: Kefei.zhang@rmit.edu.au; Tel: + +61-3-99253272; Fax: + 61-3-96632517
Received: 9 Dece mber 2004 / Accepted: 3 February 2005
Abstract. This paper introduces two sport-related
projects conducted by the Satellite Positioning and
Orientation R esearch Te am (SPOR T ) at R M IT Uni v ersi ty
– the speed sailing world record challenge and
development of a smart GPS rower tracking system. In
the first project, both traditional and contemporary
surveying technologies are investigated to assist the
Macquarie Speed Sailing Team to reliably record and
subsequently claim a world speed sailing record. In the
second project, an integrated rower tracking system has
been developed in collaboration with other research
partners and the system has been used prior to and during
the Athens Olympic Games. Three Olympic rowing
medals were won by Australia. The technology, research
procedures and maj o r developments are presented.
Key words: GNSS for sports, low-cost GPS, speed
sailing, rowing
1 Introduction
The School of Mathematical and Geospatial Sciences
RMIT University has been involved in a number of sports
related research projects in the past few years. Two
notable projects are: (1) the world sailing speed challenge
and (2) Development of a miniaturised, high precision
GPS rower monitoring and coaching system. The aim of
first project was to identify the best technology to help
the Macquarie Speed Sailing Team improve their sailing
speed recording. The second project is funded by the
Australian Cooperative Research Centre (CRC) for
microTechnology, under Project 2.5 “Interface
Technologies for Athlete Monitoring”. An aim of Project
2.5 is to develop monitoring equipment that is essentially
unobtrusive such that the athlete is virtually una ware of
its presence in training and competition. This also
includes investigation into the acquisition and
interpretation of sport’s data and its meaningful
presentation to both coaches and athletes (CRC
microTech n ol o gy, 2 0 03) .
1.1 World sailin g s pe ed re cord project
World Sailing Speed Records are awarded by the World
Sailing Speed Record Council (WSSRC, 2002), an
affiliated body of the International Sailing Federation
(ISAF, 2002). Eligible records are average velocities over
a 500-metre course by a yacht whose only method of
propulsion is the natural action of the wind on the sail. A
record will only be ratified if the attempt has been
monitored by a commissioner appointed by the
ISAF/WSSRC. The course may be defined by floats on
the water or by transit posts on shore and a timed run is
the difference between start and finish times recorded to
the nearest one hundredth of a second. Speed, distance
divided by time, is calculated to the nearest one
hundredth of a k not wi th all owanc e mad e fo r the resol ved
component of any tidal stream and/or current flow on the
course. A course is deemed unsuitable if the tidal flow
and/or curre nt exc ee d o ne kn ot.
This paper presents an analysis of both GPS and video
methods of determining sailing velocity. Simulations of
GPS position recording and video recording were made
during a recent record attempt by mounting a GPS
receiver and the video camera on the Macquarie team's
support boat (a power boat) and making three runs along
the marked course. Comparing the GPS-derived velocity
with the video-derived velocity is a useful means of
benchmarking GPS velocity against an approved
ISAF/WSSRC technique. In addition, a Kalman filter is
used to verify a simple method of determining
approximations to instantaneous velocity from kinematic
GPS.
Zhang et al.: GNSS for sports – sailing and rowing perspectives 281
1.2 CRC for micr o technology rower tracking project
The five-year project, “Development of a miniaturised,
high precision GPS rower monitoring and coaching
system”, initially investigated the feasib ility of using GPS
to aid inertial devices for Position, Velocity and
Acceleration (PVA) determination in real-time. The
positional information is then combined with other
athlete physiological information and integrated into a
dedicated electronic device to package, analyse and relay
the information to the coach. The continuous monitoring
of three-dimensional PVA of the rowing boat with a very
high frequency and accuracy is achieved through an
integration of GPS, an inertial navigation system with
sensors for athlete physiological information, a data
communication mechanism, and an interactive
visualisation procedure.
The ability to measure and record athlete physiological
information (eg. aerobic capacity, strength training and
endurance performance) and positional information
associated with athlete movement in real-time is critical
in the process of athlete training and coaching. Blood
oxygen (oxygen consumption), respiration, heart rates
(myocardial and hemodynamic responses), velocity,
acceleration/force, changes in direction and position, and
many other factors are required in elite athlete training
and coaching. The position, movement (i.e. velocity and
direction) and force (i.e. acceleration) information plays
an important role in effective analysis of the athlete
performance, especially for rowers. For example, the
stroke rate, force and synchronisation of athletes are
critical for the performance of rowers in a competition.
Currently, the stroke information can only be measured in
either well-controlled situations in dedicated sports
laboratories or using simulation devices. Much of the
equipment is either too heavy, expensive or obtrusive and
multiple factors which are difficult to control have
limited the use of sport-specific field testing. Reliable
analysis of the stroke rate and stroke length in rowing has
been a challenge for a long time due to the unavailability
of the real scenario data, in particular high-precision PVA
data (Larsson, 2003). Existing technologies used for this
purpose include theoretical studies (eg. Zatsiorsky and
Yakunin, 1991), video-footage procedure (Kleshnev,
2001), indoor tank procedure (Lin et al., 2003), computer
modelling (Atkinson, 2003; Kirtley and Smith, 1996) and
ergometer (Upson, 2003; Elliott et al., 2003). Therefore,
smart real-time monitoring during training and
competition to help elite athletes to improve their
performance and avoid injuries is critical for both athletes
and coaches.
This paper introduces an innovative "smart” GPS rover
tracking system that is currently under development at
SPORT, RMIT. This paper first outlines the main phases
in a standard rowing stroke for a better understanding of
the specific technique. The paper then briefly summarises
the proposed research methodologies for the project and
presents some selected results of recent tests. Promising
results have been obtained using low-cost GPS. It has
shown that low-cost, code-only GPS can provide great
potential for rowing applications and the stroke signature
captured from GPS is of great value for rowers and their
coaches. A prototype system has been built and the
system was extensively used by Australian rowers prior
to and in the Lucerne Regatta and Athens Olympic
Games whe re a number of gold medals were won.
2. World sailin g sp eed r e cor d s
World Sailing Speed Records (WSSRC, 2002) are
established in sail area divisions:
9 10 Sq. m Class: up to and incl u ding 10 m 2;
9 A Class: from 10 m2 up to and including 150
square feet (13.94 m2);
9 B Class: from 150 square feet up to and including
235 square fe et (21. 83 m 2);
9 C Class: from 235 square feet up to and including
300 square fe et (27. 87 m 2); and
9 D Class: ove r 30 0 sq u are fe et .
The fastest of these class records also becomes the
outright Wor l d S a iling Sp ee d Record.
In 1993 at Shallow Inlet, Simon McKeon and Tim Daddo,
sailing the triplanar wing sail yacht Yellow Pages
Endeavor, captured the B, C and D Class WSSRs on the
way to recording the highest speed ever attained by any
craft under sail of 46.52 knots. They achieved these
multiple records by adjusting the area of the wing sail
between runs. Yellow Pages Endeavour was designed and
constructed by Lindsay Cunningham and raced by a
group of volunteers. In March 2002, the group, then
known as the Macquarie World Speed Sailing Team
attempted to raise their own record above 50 knots with a
new yacht Macquarie Innovation (see Fig. 1). This yacht,
an improvement on Yellow Pages Endeavour, is a solid
wing sail attached by aerofoil sections to three small
pontoons, one of which contains the skipper and crew. In
the right wind and sea conditions, with the skipper
steering and the crew trimming the wing sail, the crew
capsule lifts clear of the water and the yacht rises slightly,
planing on the pontoons. Small hydrofoils under the
pontoons assist the hull planing and offer side force
resistance as well as steering control from the front
pontoon.
Both Macquarie Innovation and Yellow Pages Endeavour
are developments of the speed potential exhibited by C
Class catamarans, the yachts that contest the Little
America's Cup – a challenge cup, like the America's Cup,
where a sailing club challenges the cup holder (another
sailing club) to a series of match races. McCrae Yacht
Club on Port Phillip Bay, Victoria won the cup in 1985
282 Journal of Global Positioning Systems
with Victoria-150 and defended it successfully until 1996.
Victoria-150, designed and built by Lindsay Cunningham,
was the first C Class to effectively use a multi-slotted
aerofoil wing section as a sail (Landmark, 2002).
2.1 Time reco rding of the sailing r e cord attemp ts
Timing of the record attempt by the Macquarie team
employed a “clever , lo w-technology” solution dev eloped
by the team in previous attempts and now embodied in
the ISAF rules. It uses a video camera mounted in the
crew capsule and aimed to capture images of the transit
posts onshore. The camera is capable of recording images
at 25 frames per second. The transit posts, placed 8m
apart in pairs, define start and finish lines of the 500m
course (see Fig. 2). As the yacht passes the start line the
video camera records an image of two starting posts in
transit and some time later, crossing the finish line,
Fig. 1 Images of the Macquarie Innovation – a triplanar asymmetrical wing-sail yacht
sho
re
l
i
n
e
Fini
s
h
Start
Path of Yacht
500
metres
Transit Posts
8
metres
50
metres
Fig. 2 Schematic plan of transit posts defining the cou rse
Fig. 3 Diagrammatic vie w of the transit posts surveyed by both conventional and GPS methods (b) and video image frames “m” and “n” at
the sta rt (c) and finis h (a)
meticulously-shaped
steerable hydrofoils
Window for video image capture
A small pontoon at the
end of each wing
A tiny crew capsule built into the pontoon
(a) video ima ge frame “n” just
before crossing finish line
(c) video ima ge frame “m” just
after crossing start line
(b)transit post pair surv eyed by both total
station and GPS
Zhang et al.: GNSS for sports – sailing and rowing perspectives 283
records another image of the finish posts in transit (see
Fig. 3).
After a run on the course, the video is reviewed frame by
frame, noting the frame numbers m and n showing the
start and finish transits. Subtracting frame numbers and
multiplying by the frame rate gives the elapsed time,
which divided int o the distance yields the average speed.
2.2 GPS an d the transit post recording procedure
This timing technique, video camera and transit posts
described above, presents some difficulties and
restrictions for competing teams. These inclu de:
The positioning of the transit posts is critical; not
only must they produce parall e l transit lines but these
lines must be at least 500m apart and approximately
perpendicular to the path of the yacht. This
requirement necessitates a survey to mark the
positions of the posts and a plan endorsed by a
surveyor to satisfy the ISAF /WSSRC commissioner.
The yacht is restricted to sailing close to the shore
(and transit posts) so that video images of transits are
clear and distinct.
Since the yacht must travel relatively close to the
transit posts and at a great speed, there is some
danger to the crew if the yacht becomes
uncontrolla ble and co l lide s wi th the transit pos ts.
The direction of the shore (and hence the course)
limits the allowable wind direction since a yacht's
maximum potential speed is restricted to a narrow
range of wind ang les from the directio n of t rav e l.
The video camera must be calibrated to ensure an
accurate frame rat e.
Reviewing the video images is a time consuming
process and is subject to human error (errors in
visually interpreting the actual trans it).
Recognising these restrictions, the Macquarie team
approached the School of Mathematical and Geospatial
Sciences, RMIT, with a proposal to investigate the use of
on-board GPS as a more flexible means of determining
sailing velocity and distance. GPS has the following
attractions and possible advantages over the present
method.
GPS is a proven robust positioning technology, well
documented in the surveying and geodetic literature.
When used in kinematic differential mode, GPS is
capable of determining positions at centimetre level
precision at precise and regular time intervals as
small as 0.1 sec.
Kinematic Differential GPS positioning removes the
restriction of marked courses. Positions can be
determined at time intervals, say 0.1 sect∆= ,
independent of the yacht's sailing direction.
Differences in position divided by time differences,
yield velocity. In addition, simple velocity plots can
be used to determine which section of a yacht's speed
record attempt should be used to determine average
velocity.
Simulations of GPS position recording and video
recording were conducted during a recent record attempt
by mounting a GPS receiver and the video camera on the
Macquarie team's support powerboat and making three
runs along the marked course. Table 1 shows a
comparison of the GPS-derived velocity with the video-
derived velocity which is a useful means of
benchmarking GPS velocity against an approved
ISAF/WSSRC technique. In addition, a Kalman filter is
used to assess the precision of kinematic GPS positions
and verify a simple method of determining
approximations to instantaneous velocity from kinematic
GPS. Comparing the average velocities derived from
GPS observations with those derived from Video Camera
observations shows that the average differences for the
three courses are 0.017m/s for velocity and -0.026s for
time respectively. It is therefore concluded that GPS is a
viable alternative to the video camera technique.
3. Science of rowing a nd athlete tracking
Rowing is a highly developed, and becomes an
increasingly popular, international sport. It combines a
wonderful spectacle with a heated competition. Rowing
races usually cover a distance of 2,000m in river, canal or
lake-type competition environments in six lanes. To win
the competition, atheltes have to qualify through four pre-
determined rounds: the preliminary round (heats), the
repeat round (repechages), the semi-finals and the finals.
The "A" final determines the first six places and the
runners-up; the "B" final determines the next six places
(ie 7th to 12t h positions). The number of rounds per event
depends on the number of crews takin g part.
The races are judged under the supervision of umpires,
who are members of the Jury for the event. The Jury
members are placed at various locations on and off the
competition course, such as the starting line, where the
races begin under the supervision of the aligner and the
starter; along the course of the race in the competition
lanes under the supervision of umpires; the finishing line
with the finish-line umpire; the identity verification stage
of the crews before their embarkation onto the boats; the
weighing-in of the athletes; the weighing-in of boats; and,
in general, in all areas directly related to the competition,
the athletes and their equipment (Athens Olympics, 2004).
There are 14 different boat classes raced in Olympic
rowing. Thes e include eigh t sculling events in whic h two
oars are used (see Fig. 4a), one in each hand, and six
sweep-oare d e ven ts i n whi c h the row e rs use one o ar w it h
284 Journal of Global Positioning Systems
Table 1 A comparison of velocity and time derived from kinematic GPS and video cam era
GPS Video camera Differences
Course Velocity
(m/s) Time
(seconds) Velocity
(m/s) Time
(seconds) Velocity
(m/s) Time
(seconds)
A3 17.28 28.94 17.30 28.90 0.02 -0.04
A4 17.34 28.83 17.37 28.78 0.03 -0.05
A5 17.30 28.89 17.30 28.90 0.00 0.01
Fig. 4. Scul ling (t wo o ars used, one in each hand) and sweep-oared (one oar with both hands) scenarios in Olympic
competition (Athens Olympics, 2004)
Fig. 5. Schematic diagrams showing the four main sequential phases (ie. a) catch, b) drive, c) finish and d) recovery) in a
rowing stroke and the position of head, arm and legs of the rower)
both hands (see Fig. 4b). The sculling boat classes are the
single, the double and the quadrupl e sculls with crews of
one, two or four athletes respectively, as well as the
lightweight double. The sweep row categories include the
pair, the four, the lightweight four (for men only) and the
eight with coxswain.
The Athens 2004 Olympic Games Rowing events were
held at the Schinias Olympic Rowing and Canoeing
Centre from 14 to 22 August 2004. A total of 550 athle tes
(358 men and 192 women) from all over the world took
part in 14 rowing e ve n ts. F orty-five Australian rowers (28
men and 17 women) took part in 11 rowing events.
3.1 Rowing stroke
A rowing stroke is a precise movement with rowers using
their legs, back and arms to generate power. A stroke
begins with the placing of the blade in the water and ends
with the re-emergence of the blade from the water and
positioning for another cycle. The rowing stroke can be
divided into four main phases: catch, drive, finish and
recovery (Mickelson and Hagerman, 1979) (see Fig. 5).
These sequential phases must flow from and into each
other to produc e a con ti nuo us a nd fl ui d m ove m en t.
At the catch, the blade is placed into the water quickly
with minimal disturbance to the boat. The rower's arms
are extended outward, torso is tilted forward, and legs are
compressed. A good catch produces a minimal amount of
back and f r ont splash and causes no check. The catches of
all crews of a boat must be identical. Out of step catches
(unsynchronisation) cause balance problems and reduce a
boat's speed. The blade must be fully squared to the water
at the catch (RowersWorld, 2003).
The boat gains its speed on the drive. In this portion of
the stroke, the oarsman applies power to the oar with
forces from arms, back and legs, and swings his torso
away from the stern of the boat. The handle of the oar is
pulled in a clean, powerful and levelled motion towards
the bow of the boat with a constant force .
(a) 8 sculling events(b) 6 sweep-oa red events
(a) Catch (b) Drive (c) Finish (d) Recovery
Zhang et al.: GNSS for sports – sailing and rowing perspectives 285
At the finish, the oarsman finishes applying power to the
oar handle, removes the blade from the water sharply, and
feathers the oar (rotate it by 90º) so that the blade
becomes para l le l to the su r face of the water.
At the recovery, rowers are given a brief rest to prepare
for the next stroke. The oarsman must slide towards the
stern of the boat and prepare the blade for the next catch.
Crews exhibit an approximate 2:1 ratio between the times
spent on the recovery and the times spent on the drive. At
the end of the recovery, the oar is gradually squared and
prepared for the catch (ibid .).
Understanding which movements should occur in each
phase of the stroke allows coaches to design effective
conditioning programs and evaluate rowing performance
effectively. Success in competitive rowing is achieved by
taking the shortest time to complete a course (usually
2000m) wh i ch directly li nks to the av erage velo cit y of the
boat. Acceleration is proportional to force since the boat
is accelerated as it reacts with th e s weeping arc of the oar.
Three factors affecting boat velocity are: stroke power,
stroke length and stroke rate. These factors are important
determinants of rowing performance. The stroke power
determines how fast the boat travels in a stroke, the
length is associated with how far t he boat travels in each
stroke and the rate is the number of strokes rowed per
minute (Seiler, 2003). Therefore the rower must achieve
an optimal combination of high stroke power, long stroke
length and high stroke rate.
Fig. 6 presents the stroke signals captured using geodetic-
type GPS receivers. It is demonstrated that the signals
captured provide a clear picture of the rowing stroke
phases as described above. In this particular stroke, the
graph indicates that the rower has harmonised well in his
stroke cycle by using appropriate time (1:2) in the catch
and the drive.
3.2 Indoor training usin g ergome ter
Fig. 7 shows a typical athlete training procedure in an
indoor environment using an ergometer (O'Sullivan and
O'Sullivan, 2001). Much of the equipment is either too
heavy, expensive, obtrusive or unreliable. Therefore,
smart real-time monitoring during training and
competition to help elite athletes to improve their
performance and avoid injuries is critical for both athletes
and coaches. Any methodology that would improve the
situation would not only bring benefits to the rower
practice, but also to many other sport-related applications
including both team sports and individual athletes (eg.
Zhang et al., 2 003) .
A major step forward would be achieved by a
comprehensive system that could be used to obtain
physiological information of the athlete together with
precise movement information through an independent
platform which is a low-cost, low-maintenance,
miniaturised and integrated sensor system. GPS has been
identified as a key element to the success of the project.
Such a system is clearly ambitious and will not be
achieved in a single step. This project will provide a
starting point towards this ultimate goal, through the
combination of advanced global navigation satellite
systems technology, smart wireless communication, on-
line signal processing and GIS, to measure movement
information in real-time to a high precision.
4. Developmen t of GPS Based Pro tot yp e System
In many sports, it is desirable for movements to be
repeated multiple times to obtain a consistent positive
result. A greater understanding of sensor-based human
performance measurement, such as the determination of a
characteristic signature of the "perfect" movement, is
required to a nalyse the pe rforma nce o f the athl ete (Sei ler,
2003). Therefore, the ability to measure and record
positional information together with athlete physiological
information in real-time is critical to the process of
athlete training and coaching. Physiological information
can be relativel y easy to o bta in usin g relevant detec tor s as
described above. However, real-time high precision
positioni ng of th e athlet e has been a challeng ing task (eg.
Fyfe et al., 2001; Hutchings et al., 2000; Larsson, 2003).
A prototype rower tracking system has been developed.
Fig. 8 outlines the system architecture and Fig. 9 presents
the major phases of the development. Online calculation
and a user friendly visualisation mechanism is also
integrated into the system.
4.1 Low-cost cod e GPS
A number of critical factors contribute to the applicability
of the GPS system to rowing practice. This includes the
precision, cost, volume and weight of the system, and its
integration with other sensors including accelerometers,
communication mechanism, and a personal digital
assistant (PDA). In spite of the “high-end” geodetic-type
receiver providing very high precision results, its
disadvantages are the requirements of differential
operation, large on-line data processing power and
establishment of an independent base station. The cost,
volume and weight of this type of GPS receiver and its
sophisticated operational procedure unavoidably preclude
its practical us e.
Because of the challenges of diverse applications and a
broadening market, the low-cost GPS has evolved
significant l y d uring t he past deca de (X ia o e t al. , 2003).
286 Journal of Global Positioning Systems
Fig. 6 Schematic rowing stro ke signature capture d from high precision GPS mea surement (Trimble 5700, 10Hz)
Fig. 7 Typical indoor training instrument (ie. ergometer) and athlete perform ance and information collection procedure
using the concept II indoor device with various physiological sensors attac hed
Fig. 8 Skeleton of the system structure of the “smart” rower tracki ng multi-sensor system wi th wireless communication and on-line
processing functionalities.
Multiple p hys iol o gica l se ns or s
(eg heart rate, blood pressure)
Concept II indoor
rowing machine
Multiple sensor
system
Positioning
sensors
Athlete boa t
Wireless
communicatio
Coach boat
PDA
Zhang et al.: GNSS for sports – sailing and rowing perspectives 287
Fig. 9 Development roa dmap of the prototype rowing tracking system
Increasingly miniaturised devices have been developed to
be wearable and embedded in other devices. Significant
new developments of the low-cost GPS units are listed
below.
¾ The ability to process weak GPS signals,
¾ Combined functionality and integration with other
systems such as cellphone or other wireless
communication systems (eg. Bluetooth (2003), PDA,
and Internet browser),
¾ Full compatibility incorporating GPS with other
devices, and
¾ Reduction of power consumption, size and weight,
and price.
Given these developments, the feasibility of the low-cost,
code-only GPS receiver has been investigated and the
performance of a low-cost receiver is presented in the
next section. A code GPS receiver and a personal digital
assistant (PDA) that form the first version of the
prototype system are shown in Fig. 10.
4.2 Low-cost car rie r GPS
A rower tracking system with the functionality to output
PVT information at a rate of 10 Hz has been found
necessary and essential in the rowing experiments. In
order to develop such a system, a Canadian Marconi
Company’s (CMC) SuperStar II GPS OEM board is used
to form the hardware basis of the system. The SuperStar
II can provide PVT s olut ion at a rate up to 5 Hz as well as
raw measurements at a maximum rate of 10 Hz. The raw
measurements include code phase, carrier phase and
signal-to-noise ratio (SNR). Robust algorithms and
associated software/firmware have been developed and
the current prototype system configuration is shown in
Fig. 11(a). The algorithms for PVA solution are
developed using a number of special treatments for
rowing-specific application. These algorithms have been
evaluated through a number of static and kinematic trials
as shown in section 5. More rowing trials are on the way
and further ref inement of algo rithms is being un dertaken.
Fig. 10. Configurat ion o f the low-cost c ode GPS (1Hz) system
5. Field exp erim ents and r esults
A number of rowing trials have been conducted to assess
the performance of both high-end and low-cost GPS
systems and to identify potential problems in the river
environment. RTK GPS has been proved to be able to
provide high precision positioning in a lake environment.
However, there are a number of considerations: multipath
effects, signal obstruction, satellite visibility, and
obtrusion etc. Ideally the presence of any instrument
should not cause direct visual or physical impact on the
Stage 1: Real-time
kinematic GPS
Concept demonstration
GPS availability in rowing
Feasibility investigation
Stage 2: Low-cost code
GPS
Low-cost, light and low
power cons umption co d e
GPS availabilit
y
Stage 3: Low-cost carrier
GPS
Cover over w h o le freq ue ncy
band of rowin g m ovem e nt
Enhance robustness; provide higher output rate;
cover a wid e r frequency band of moveme nts in sports
Stage 4: High level system
development
system miniaturisationand
functionality integration
Integrated with
other sens ors
blood press ure,
heart rate,
aspiration,
IMU/INS
wireless
video
Low-cost
GPS receiver
Batter
y
and cables
PDA
288 Journal of Global Positioning Systems
Fig. 11 A compact prototype rower tracking system (a) and photo of James Tomkins and Drew Ginn who won men’s pair gold medal (b) in
Athens Olympics
athlete. Therefore, the size and height of the antenna is a
primary cons id e rati on.
The solution from geodetic-type GPS receivers acts as the
reference while evaluating the solution of c ode-only GPS.
The base station is located on the bank of a river about
~2km away from the course of the boat trial. The ba se line
solutions from each of the rowing antennas were
processed independently from the base station using the
post-proce sse d kinem at ic tec h nique .
If assuming that the accuracy of the position to one GPS
rover is the same as to the other, then, from the simple
(Least Squares Adjustment) error propagation law, the
accuracy of the position of the kinematic GPS
measurement (for a single baseline) can be estimated. A
few millimetre accuracy of the antenna height was
achieved in a three (consecutive) day trial (Zhang et al.,
2003). Given the closeness of the antenna and the
reflective nature to the water surface, the performance of
the PPK GPS pr esents consistent results.
An important task of this project was to test the
performance of a code GPS receiver which provides low-
cost and light weight , less compl i cat ed operation , an d less
communication and storage requirements. Two
procedures were used to test the performance of the low-
cost GPS receiver: comparison with the high-end GPS
receiver and zero motion test of the code GPS receiver
(static performance) (Zhang et al., 2003).
Fig. 12 shows the mounting of the two types of GPS
receiver (high-end carrier phase Trimble 5700 and low-
cost code-only Rojone Genius 1 receivers). Note that the
reflective nature of the water surface environment
normally causes a high potential multipath effect which
could contribute to a large amount of error (upto a few
meters for the code GPS receiver). It was expected that
elevating the antenna could potentially mitigate multipath
effects. Contrary to expectations, the results indicate no
significant multipath effects, which will provide guidance
for antenna mounting in future trials.
Fig. 13 shows the boat trajectory of the trial for a ~1.5
hour “run”. The continuity of the raw GPS measurements
and solutions is evident. A close examination indicates
that over 99.9% epochs have been resolved with a
consistently high level of a ccuracy.
Fig. 12. RTK geodetic (carrier phase) and low-c ost (code-only) GPS
receivers mounted on the same boat
RTK GPS
Low-cost GPS
(a) (b)
Fig. 13 Boat/rover trajec tory obtained from code GPS
Longitude (degree)
Latitude (degree)
Zhang et al.: GNSS for sports – sailing and rowing perspectives 289
6. Conclusions
This paper presents two applications of the GNSS
technology in sports: sailing and rowing. Determination
of the sailing course at Shallow Inlet for the recent
attempt on the World Sailing Speed Record and the
feasibility of using GPS technology is described. It is
shown that GPS is a superior technology to the current
video camera procedure for speed recording. As a result
of RMIT Satellite Positioning and Orientation Research
Team (SPORT) findings, the Australian team has
received World Speed Record Council approval to
introduce the method of timing demonstrated in this
paper for world record attempts.
This paper also outlines SPORT involvement in the
recent development of the CRC for microTechnology
Project 2.5. It is demonstrated that low-cost GPS
receivers can provide high-accuracy velocity and
acceleration information. It shows the feasibility of GPS
technology to assist in elite rowing training. It has been
demonstrated that the stroke signature captured from GPS
is of great value for the investigation of, for example, the
duration of the drive and recovery phases, the total time
per stroke cycle, drive to recovery ratio, and the
relationship of the hands and seat during the drive phase.
A number of prototype rower tracking systems have been
developed and used by Australian athletes prior to and
during the Athens Olympics. Gold was struck twice as
Australia came in first in the Men’s Quad Skull. Australia
snagged thr e e row i ng m eda ls ( go ld, silver an d br o nze) .
It has clearly been shown what can be achieved through
“smart” integration of GPS and other advanced
technologies for innovative sports a pplications.
Acknowledgements
The rower tracking project is funded under the CRC for
microTechnology Project 2.5. The authors would like to thank
Prof A. Hahn, Dr C. Gore and Dr A. Rice from the Department
of Physiology, Australian Institute of Sports for their assistance,
support a nd co-operation.
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