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Setting up Navi GT31
resource website by
GT32-50 is a new instrument that combines GPS-Doppler
with inertial navigation technology and magnetometer to enhance
measurement of motion. GT32 contains two GPS-Doppler
engines and 3-axis alias-free DC accelerometer sampling at 50Hz
(providing 150 acceleration samples per second), all logging to
SD card in compact binary format.
GT32 has evolved from GT31 and can be described
as "9 instruments in one", all fitting into a single
GT31 case and sharing one SD card. In essence, an additional hardware
module has been fitted inside GT31 to extend its capabilities.
This extra module comprises an autonomous gps-Doppler engine,
three DC accelerometers 3D magnetic compass and a thermometer.
GT32 is aimed for people who want to measure jumps and
acrobatics or carry multiple GT31 units in their effort to improve
motion measurement accuracy. GT32 is cheaper and
more compact than two GT31 instruments. In addition, GT32 offers
possibilities that are beyond reach of a pair of GT31 units, such
as higher bandwidth and detection of angular orientation (yaw, pitch,
roll angles) of a moving craft, or in sport for example.
This website contains links to technical, theoretical, scientific
and software resources to assist GT32 users to make the most of
their GT32 instrument.
Using new GT32
50Hz instrument offers many interesting possibilities in sport
and other activities:
- it can measure 3D speed simultaneously using 3 independent
ways (2*GT31 GPS-Doppler and 1 integration of accelerations)
- it can measure jumps and acrobatic maneouvres in many sports
(windsurfing, kitesurfing etc..)
- can increase the bandwidth of motion measurements beyond limits
of the GPS technology alone
- less bulk to carry than two separate GT31 instruments
- Potential for detection, verification and correction of gps-Doppler
aliasing problems (during sailing and speed record attempts
- No kinematic differences between two internal GT31 gps-engines,
because they share the same GPS antenna. This improves repeatability
and reproducibility of speed measurement, reduces error margins
in speed measurement and enables calibration of gps-Doppler
- Potential to measure motion parameters (such as speed for
example) 50 times per second, because integrated and aligned
accelerations can be used to fill-in gaps between 1Hz GPS-Doppler
- potential to measure the angular orientation of craft in motion
(yaw, pitch and roll angles)
Some of the above potential can be used today using the existing
GPS software tools, some require development of new tools. My
view is that progress cannot really be stopped, so it is better
to support it.
|For latest GT32 firmware
please see GT31
firmware update page.
GT32 generates a
single "extended SBN" file that contains GPS data from
2 independent GT31 chipsets plus 3 sets of 50Hz acceleration data
(150 acceleration samples per second) and temperature readings.
Before standard GPS-data processing software is improved to access
the second gps-engine data inside "extended SBN file"
I provide a simple software utility to extract "internal
gps-engine" data into a separate SBP file.
Downoad GETSBP utility, unzip it, and
provide a shortcut to it on your desktop. Then drag-and-drop GT32-generated
SBN file to this shortcut. GETSBP will generate SBP file in the
same folder as the original SBN file. This extracted SBP file
will have name similar to source SBN, but will end with "-a.SBP"
Both SBN and extracted SBP file can be viewed and processed using
standard GPS data processing software.
Software developers: please contact
me for details of SBP, acceleration and temperature records
in "extended SBN" file.
are 2 methods of setting-up Settings in GT32
- manual: using buttons
in GT32 itself. Setting up process is essentially the
same as for GT31, with some extra steps: setting D0,D1,D2,D5
=ON and D3,D4 =OFF in MISC menu.
- using NavilinkII : this
method enables you to backup/share/restore complete set of GT31
settings. Download my GT32
settings file and use NavilinkII>Settings>Write function
to load this setting file to your GT32. Please check if D0,D1,D2,D5
=ON and D3,D4 =OFF in MISC menu. You may wish to change the
"time zone" in Settings as well.
Theory and publications
 T.J.Chalko, Reconstructing data from alias-free discrete series
of samples, NU Journal of Discovery 2009, http://nujournal.net/Fourier.pdf
 T.J.Chalko, Combining accelerations and GPS-Doppler velocities,
NU Journal of Discovery (draft 2010) http://nujournal.net/accDoppler.pdf
 T.J.Chalko, Estimating Accuracy of GPS Doppler Speed Measurement
using Speed Dilution of Precision (SDOP) parameter, NU Journal
of Discovery 2009,