OXTS xNAV650 User manual

xNAV650 QUICK
START GUIDE
The high performance, lightweight, INS for
multiple applications

Green. Power applied to system
Orange. Trafc present on Ethernet
Red ash. The operating system has
booted but the GNSS receiver has
not yet output a valid time, position,
or velocity
Orange. The INS has initialised and
data is being output, but the system
is not yet real-time
Green. The INS is running and the
system is real-time
Red and green ash. The system is
asleep. Contact OxTS support for
further information
Red. The GNSS receiver has a
differential heading lock
Orange. The GNSS receiver has a
oating (poor) calibrated heading
lock
Green. The GNSS receiver has an
integer (good calibrated heading
lock
Red ash. The GNSS receiver is
active but has not yet determined
heading
LED states
Power
Status
GNSS
Red.The GNSS receiver has locked-
on to satellites and has adjusted
it’s clock to valid (1 PPS output now
valid). The INS is ready to initialise
Key PointsKey Points
Key considerations
/Excitation of the IMU sensors is the essential
requirement of a warm-up. To encourage optimum
performance, the warm-up should be performed in a
similar style as the survey but with more manoeuvres
(without saturating). This is needed for the Kalman lter
to make the correct decisions for scaling the sensor
output during the survey.
/If the Kalman lter has not experienced dynamics of
a certain type before, the output is likely to be scaled
incorrectly as it estimates what the scaling should be. It
is unlikely to estimate perfectly at the
rst attempt.
Why warm up?
/ Georeferencing requires accurate time, position
and orientation.
/ To achieve accurate output of these measurements, the
xNAV Kalman lter monitors states of:
1. GNSS antenna position
2. GNSS antenna orientation (dual antenna)
3. IMU sensor scale factor and biases
4. Live position and velocity errors
/ As a result, the raw data provided by the GNSS receiver
and IMU needs to provide a varied range of data to give
the best opportunity to improve all those states.

Initialise
/ If using a land vehicle use “dynamic initialisation” and
accelerate up to the initialisation speed (5 m/s). Ensure
you maintain trajectory until initialisation is complete.
/ If using a UAV ideally use “static initialisation” offered
by the dual antenna setup, as this will enable the most
reliable heading output with respect to due north.
/ Ensure you are in a clear GNSS environment, if using
“static initialisation”.
/ If using single antenna to initialise, accelerate your
vehicle to exceed the initialisation speed (5m/s by
default). Try to avoid initialising the system with a
signicant pitch or roll value (ideally greater than 5°).
Congure in NAVcong
/ Congure your orientation settings to match the vehicle
or the coordinate system in which you want the INS to
output. Make sure the “forward” axis matches between
the INS and your relevant coordinate system.
NOTE: These orientation settings will dene the axis
directions for all lever arm measurements later in the
NAVcong process.
/ Set up the remainder of your conguration,
ensuring that you set up your LiDAR/camera sensor
synchronisation settings if using. Most settings can be
optimised in post-processing, but the synchronisation
must be correct in real-time.
/ Maximise the separation of GNSS antennas for the best
heading performance.
Setup
Install hardware
/ Mount the INS in/on the vehicle
/ Position the GNSS antennas and measure the lever
arms to the INS measurement point
/ Connect the GNSS cables and user cable
/ Supply power
/ Set up IP connection to the device on the same IP range

Warm-up
Warm-up
/ During the opening 1-3 minutes (3 mins for a new
installation, 1 min for an optimised setup) the Kalman
lter will optimise several real-time states to rene the
data output to be as accurate as possible.
NOTE: This warm-up period can be further reduced by
using OxTS’ combined post-processing solution.
/ During this warm-up period, it is important to exert the
INS to dynamic motion that will help to resolve any
errors and unknowns in the conguration, particularly
GNSS lever arm errors.
/ Perform suitable manoeuvres in your test area that
exert signicant ‘but safe’ values of acceleration on
the accelerometers and gyroscopes (linear and angular
acceleration are needed in both positive and negative
directions of every sensor).
/ Try to take advantage of the 3D freedom of motion that
a UAV has; perform vertical manoeuvres as well as
horizontal “gure-8” style movements.
/ Monitor the real-time states of the system in
NAVdisplay’s performance template, if a data link is
available, to know when you are ready to survey.
/ If any accuracy valve looks poor, try to perform a
manoeuvre that would excite the INS in that way. To
overcome poor heading, perform “gure-8” motion.

Validate and Commit
Validate cong
/ Stop the vehicle and review the live system accuracies
in NAVdisplay to ensure every state is optimised.
/ If a conguration has been validated in previous surveys
then the user will build condence in their warm-up
procedure, allowing for the survey to start almost
straight away.
(Optional) Commit optimised settings
/ With the system fully warmed up, you can reopen
NAVcong and commit the real-time optimised settings
back to the xNAV to use them from startup in every
future data collection.
/ It is important that this feature is only used if you are
leaving the xNAV permanently installed in the vehicle. If
the xNAV is moved, then this process will become void
and future data may not relate correctly to the vehicle in
which it is mounted. This step can be completed after
the survey is nished or even back at the ofce.

Warm-down
Survey
/ Fly your survey route, intermittently review system
accuracies in NAVdisplay if a data link
is available.
NOTE: Avoid spending extended periods in GNSS-denied
environments so that the IMU does not drift.
/ Try to include acceleration throughout the survey to
keep the kalman lter up to date.

Survey
Warm-down (for post-process)
/ Repeat the warm-up procedure at the end of the survey
to provide similar linear and angular acceleration to the
system as the initial warm-up.
/ Be sure to recreate the “reverse” of the initialisation
process (for backwards post-processing), i.e. for “static
initialisation” allow the vehicle to remain stationary for
at least 1 minute before powering down (ideally leave
more time, especially in a poor GNSS environment).
/ If using single antenna dynamic initialisation, brake
to a stop in a straight line from above the congured
initialisation speed (5 m/s by default).
Download data
/ It is possible to download the data from the system
immediately, via NAVsolve or FTP, or later. The onboard
storage will save the raw data automatically.

Need further
assistance?
Visit the support website:
support.oxts.com
Get in touch if you can’t
nd what you need:
[e-mail]
[phone]