OXTS xNAV Operating and maintenance instructions

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Version: 140626 110202
xNAV quick start guide
Version:
140623
Author:
BG
List of contents
1. Installing an xNAV..........................................................................................................................1
2. Positioning the antennas...................................................................................................................2
3. Configuring an xNAV......................................................................................................................2
4. LED states........................................................................................................................................3
5. Initialisation and warming up ..........................................................................................................3
6. Downloading and viewing data........................................................................................................3
7. Revision history ...............................................................................................................................4
This quick start guide covers the basics of installing and operating an xNAV system. More detailed
information can be found in the full user manual.
1. Installing an xNAV
When mounting an xNAV, it is important to ensure there can be no movement relative to the body
being measured, as this will affect the accuracy of your measurements. The xNAV can be secured
using the M3 mounting holes on the side of the body and the pre-formed 90° brackets that are
supplied with each system. Brackets allowing an xNAV to be attached to an RT-Strut for use in
road vehicles is also available as an optional extra.
The standard orientation of the measurement axes are shown in Figure 1. This orientation is
common to all models of xNAV, and is marked on top of the xNAV along with the origin of the
inertial measurement unit (IMU). By default the xNAV expects its y-axis to point right and the z-
axis to point down, although it can be mounted in any orientation as long as this is defined using the
NAVconfig configuration software.
During configuration, remember that measurements should be made to the IMU origin indicated on
the lid, not to any other point on the system. The xNAV will automatically re-orientate its output
measurements using information provided during the configuration process.
It is not vital to precisely align the xNAV’s axes to the
body being measured as the system is capable of
automatically resolving many of these. However, to
quickly achieve the best results, you should aim to align
them as closely as possible.
A dc power supply between 10–31 V and capable of
delivering 7 W will be required. Power is delivered via
the main connector. This connector is keyed and should
not be forced in. Rotate the connector until it inserts
easily. When inserted properly the connector locks to
Figure 1. Orientation of xNAV axes

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avoid accidental disconnection. To remove the connector pull back on the spring-loaded collar—
this releases the locking mechanism. Do not pull on the cable.
2. Positioning the antennas
The GNSS antennas should be positioned
with a clear, unobstructed view of the sky,
on a metal surface and 20 cm from any
edge where possible. With dual antennas,
the heading accuracy is dependent on the
separation distance. The specification is
valid for a 2 m separation. A smaller
separation can be used but the heading
accuracy will degrade. The system
supports up to a 5 m separation. It is
important to ensure the orientation is the
same for both antennas. They should be
rotated so the cable exits each antenna at
the same angle when viewed from above.
The xNAV needs to know the separation
of the antennas to within 5 cm. Angular
offsets can also be defined in the configuration software. All measurements should be made as
accurately possible.
3. Configuring an xNAV
An xNAV is configured using NAVconfig, which is supplied with the bundled software. Once
installed, you can find the program by clicking Start > All Programs > OxTS > NAVconfig. The
configuration process is quite intuitive and should be easy to follow. In most cases you will only
need to make the following changes:
Step 1 of 10 Select xNAV from the Product family, and then select the correct model.
Step 2 of 10 Select Use default settings.
Step 3 of 10 Not used.
Step 4 of 10 Set the Y axis points and Z axis points options to match your installation.
Step 5 of 10 Measure from the xNAV’s IMU origin (shown on the lid) to the primary antenna
along the three vehicle axes and enter the measurements.
Step 6 of 10 Select Enable secondary antenna and enter the distance between the antennas.
Try to measure to within 5 cm. Set Position of the antenna to match your
installation.
Step 7 of 10 If the xNAV is installed in a land vehicle with a non-steered axle this option can
be enabled. Measure the distances from the xNAV origin to the axle
measurement point (Figure 3) in the same way as in Step 5.
Step 8 of 10 There are a number of options available to tailor the outputs of the xNAV for
certain situations. The default settings are sufficient for many applications. See
the user manual for explanations on the individual options.
Figure 2. Antenna installation. Distance x should ideally be
between 1 and 5 m.

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Step 9 of 10 If an xNAV is connected and turned
on, the IP Address of the xNAV
that you want to configure should
be available. Select an address and
click Commit.
Step 10 of 10 The configuration is stored
internally on the xNAV once
committed but a copy can also be
stored locally if necessary.
4. LED states
The LEDs on the front of the xNAV are designed to provide as much feedback as possible to users.
During normal operation, the LEDs should behave as follows:
PWR Green when power applied to system. Orange when traffic present on Ethernet.
STATUS Flashing red while searching for GNSS lock. Solid red when ready for initialisation.
Orange after initialisation, outputs not yet real-time. Green when INS running and
outputting in real-time.
GNSS Flashing red while searching for heading lock. Solid red/orange/green for
differential/floating/integer heading lock.
5. Initialisation and warming up
After powering the system and achieveing GNSS lock, the system must be initialised before it can
start outputting data. This is done by travelling forwards in a straight line and exceeding the
initialisation speed (default 5 m/s).
In order for the Kalman filter to tighten its model of the system, it is necessary to warm the system
up for about 15 minutes. This helps the Kalman filter learn about configuration and sensor errors.
During this period the body being measured should be driven or flown in a way that excites the
accelerometers and gyros about each axis. For land vehicles, this means driving figures of eight
with some acceleration and braking. For aerial vehicles, the system should be flown in a similar
way, but with the addition of climbs and dives. Once the system has warmed up it should be left on.
Turning it off will require the warm up process to be repeated.
6. Downloading and viewing data
Data is downloaded from the xNAV using RT Post-process. By default xNAVs are configured with
an IP address of 195.0.0.sn, where sn is the last two digits of the device’s serial number. The IP
address of the PC used to configure the xNAV will need to be set in a similar range (suggested
195.0.0.5).
With data downloaded directly from the xNAV, once the raw RD files have been post–processed,
the newly created NCOM files can be viewed, manipulated and exported using NAVgraph, which
can be found in the OxTS folder under the start menu.
If you require assistance, please contact your local OxTS representative or [email protected].
Figure 3. Measurement point for a non-steered
axle

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7. Revision history
Revision
Changes
Draft
Initial draft
140623
Software suite names changed, image change, updated to apply to real-time xNAVs.
140626
Changed LED section, added initialisation paragraph.