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Paul Treffner
03-21-2000, 10:30 AM
Summary of query on Global Positioning Systems (GPS):

ORIGINAL QUERY:

We have a project to investigate the biomechanics and dynamics
of automobile driving around a driving track. We need measures of
vehicle position. We think we could use GPS to obtain an *accurate*
measure of position over time (using data-logging). As off-the-shelf
GPS (e.g., for hiking) is of no use (accuracy approx. 30 m), we will
need to buy a Differential GPS (DGPS) system that can provide
sub-meter accuracy at rates in excess of 1 Hz (more like 5Hz). But
they are pricey.

Has anyone out there dealt with this problem? If so, I would be
grateful to receive any information on suppliers, technical
specifications, and of course, prices. I shall summarize for
Biomech-L the replies. Note, GPS and related technology is likely to
be the "wave of the future" with regard to obtaining in-the-field
kinematic measures of the control and coordination of everything from
geese to footballers to space planes - probably in the not too distant
future...

Thanks,
Paul

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REPLIES:

From: Peter Sinclair

You might try contacting someone from Aeronautical engineering at
Sydney Uni. I remember meeting someone there who was using
differential GPS to control unmanned aircraft. They claimed to have
enough resolution to control the pitch of the plane by mounting a GPS
module on each wing and comparing the calculated height above ground.
Unfortunately, I can't remember who I was talking to. You will have to
send a general inquiry to someone in that department
(http://www.aero.usyd.edu.au/).
School of Exercise and Sport Science
The University of Sydney
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From: Richard Smith

That's not true. My six degrees of freedom
inertial segment datalogger will do the same for every segment!
Range/price: 2 km range at $25k.
Faculty of Health Sciences
The University of Sydney
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From: Ben Hale

A cheap solution that might or might not
work: if you have two recording devices available- you might get by
with two of the cheaper, non-differential units. Just have one
stationary and one in the moving vehicle, and take the difference
between the two to get rid of the offset.
Hopkins Marine Station
Oceanview Blvd. Pacific Grove, CA 93950 Lab: (831) 655-6208 Home:
(831) 372-4519
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From: "Gunter Siegmund"

We have used DGPS to monitor vehicle position in
a study of long-haul truck driver fatigue. A description of the
methods is given in a technical paper (see citation below) and is
available through the Society of Automotive Engineers (www.sae.org).
Our study was conducted back in 1993, so I don't know whether this
information is stale or not. In brief, we used three Trimble Land
Surveyor 4000SE receivers: one as a base station and the other two as
rovers on two different vehicles. Sampling was limited to 2 Hz. We
rented the equipment because at the time this technology was still
expensive (Can$10,000+ for the equipment we used). Long
post-processing times were needed (about 2.5 times the duration of the
test), however newer PCs and GPS equipment have no doubt reduced this
time. We were able to resolve displacements of about 2-3 cm and
successfully used the data to monitor both vehicle following distances
and lateral position of the vehicle within the lane. We conducted our
study on an airport runway and therefore has no trouble remaining in
contact with the satellites. The more satellites you can "see", the
better the resolution of your measurements. In '93, we had to plan our
tests based on the number of satellites which remained at an altitude
of about 15 degees above the horizon for the estimated duration of our
tests (max ~ 4 hours). Presumably there are more satellites now and
this will be less of a problem. King DJ, Siegmund GP, Montgomery DT
(1994). Outfitting a Freightliner tractor for measuring driver fatigue
and vehicle kinematics during closed-track testing (paper no. 942326).
Warrendale, PA: Society of Automotive Engineers.
Biomechanics Lab,
School of Human Kinetics University of British Columbia, Vancouver,
BC, Canada http://www.hkin.educ.ubc.ca/pages/biomech.htm
Principal,
MacInnis Engineering Associates 11-11151 Horseshoe Way, Richmond, BC,
Canada, V7A 4S5 http://www.maceng.com
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From: Trimble NZ Support

I have forwarded your email to Herga
Instruments, our dealer in Queensland. They should be able to give you
an idea of what Trimble GPS products are available and their prices.
If you want to contact them yourself their contact details are:
Herga Instruments 33 Allison Street Bowen Hills, QLD 4006 Australia
Ph +61 7 3852 1245 Fax+61 7 3252 1275
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From: "Philippe Terrier"

Our group utilizes GPS technology to study
human locomotion since 1997: Schutz Y, et al. Could a satellite-based
navigation system (GPS) be used to assess the physical activity of
individuals on earth? Eur J Clin Nutr. 1997 May;51(5):338-9. 3 other
papers are "in press", read carefully the "literature update" in
biomech-L ;-) You can find some indications about one of our current
projects at http://dgrwww.epfl.ch/TOPO/recherche/recherche3.htm. It is
possible to assess position with a centimetric accuracy by using for
exemple Leica 500 system (5Hz measurment frequency) or Ashteck Javad
(10Hz (20Hz implemented but not functional now)). This device is the
best actually in the market: it use both Navstar and Glonass (russian)
satellites, work at high frequency, is relatively lightweight (2.5
kg), can resolve the ambiguities very fast (no static initialisation).
You can directly obtain Doppler speed with an accuracy better than
0.6cm/s. Data are stored on PCMCIA memory card, but you can also work
"on line" with differential correction transmitted by FM. One
drawback: always keep in mind that GPS receivers need to directly
access to satellites (4 minmum, but 5-6 for high precision): a tree
can stop the signal ! Of course you need two GPS receivers to perform
differential carrier phase recording. It's very expensive (30000$),
but you can find 1Hz receiver recording differential smoothed code
with an accuracy of a few meter for less than 1000$...
Insitute of Physiology, Lausanne, Switzerland
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From: Dieter Rosenbaum

You should contact Ewald Hennig (if he does not
respond directly) at: ewald.hennig@uni-essen.de
Funktionsbereich Bewegungsanalytik
Movement Analysis Lab Klinik für Allgemeine
Orthopaedie - Orthopaedic Department Westf. Wilhelms-Universitaet
Muenster - University of Muenster Domagkstr. 3 D-48129 MUENSTER
Germany
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From: Ewald Hennig