OXTS RT Series User manual

xF
Confidently. Accurately.
RT
v2
GNSS-
aided
inertial
measurement
systems
User Manual
Covers all RT models

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Oxford Technical Solutions
Legal Notice
Information furnished is believed to be accurate and reliable. However, Oxford
Technical Solutions Limited assumes no responsibility for the consequences of use of
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may result from its use. No license is granted by implication or otherwise under any
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Limited products are not authorised for use as critical components in life support devices
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Waste electrical products should not be disposed of with household waste. Please recycle
where facilities exist. Check with your Local Authority or OxTS representative for
recycling advice.

RT User Manual
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Copyright Notice
The software is protected by copyright of Oxford Technical Solutions at oxts.com.
© 2008–2019, Oxford Technical Solutions Ltd.
Unauthorised use, copying or distribution is not permitted.
The software also includes software in binary form from:
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Copyright (c) 2002, Xiph.org Foundation
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© 1982–2008, QNX Software Systems Ltd. All rights reserved.
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Copyright (C) 1999–2013,2014,2015,2016 Jack Lloyd
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All rights reserved.

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Revision
Document Revision: 190130 (See Revision History for detailed information).
Contact Details
Oxford Technical Solutions Limited
77 Heyford Park
Upper Heyford
Oxfordshire
OX25 5HD
United Kingdom
Tel: [phone]
Web: http://www.oxts.com
Email: [email protected]

RT User Manual
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Warranty
Oxford Technical Solutions Limited warrants its products to be free of defects in
materials and workmanship, subject to the conditions set forth below, for a period of one
year from the Date of Sale.
‘Date of Sale’ shall mean the date of the Oxford Technical Solutions Limited invoice
issued on delivery of the product. The responsibility of Oxford Technical Solutions
Limited in respect of this warranty is limited solely to product replacement or product
repair at an authorised location only. Determination of replacement or repair will be
made by Oxford Technical Solutions Limited personnel or by personnel expressly
authorised by Oxford Technical Solutions Limited for this purpose.
In no event will Oxford Technical Solutions Limited be liable for any indirect, incidental,
special or consequential damages whether through tort, contract or otherwise. This
warranty is expressly in lieu of all other warranties, expressed or implied, including
without limitation the implied warranties of merchantability or fitness for a particular
purpose. The foregoing states the entire liability of Oxford Technical Solutions Limited
with respect to the products herein.

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Oxford Technical Solutions
Table of contents
Introduction 10
Easy operation 11
Self-correcting 11
Interchangeable 11
Advanced processing 11
Related documents 12
RT product family 13
Single antenna 13
Dual antenna 13
GLONASS 14
250 Hz 14
Satellite differential corrections 14
Scope of delivery 16
RT2000 system components 16
RT3000 system components 17
RT4000 system components 18
Specification 20
Common specifications 24
Notes on specifications 24
Heading accuracy 25
Environmental protection 25
GNSS antenna operating temperature 25
Safety information 25
Export control classification number 25
Conformance notices 27
Regulator testing standards 27
Software installation 29
Hardware installation 31
RT orientation and alignment 31

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Antenna placement and orientation 31
Operation 33
Front panel layout 33
LED definitions 35
Co-ordinate frame conventions 37
IMU frame 37
OxTS NED navigation frame 39
ISO 8855 ENU earth-fixed system 39
OxTS horizontal frame 40
ISO 8855 intermediate system 41
OxTS Vehicle frame 42
ISO 8855 vehicle system 43
Ethernet configuration 43
Connection details 45
Dual antenna systems 46
Multipath effects on dual antenna systems 48
Inputs and outputs 49
Digital inputs and outputs 49
1PPS output 50
Event input 50
Wheel speed input 51
Wheel speed output 51
IMU sync output pulse 51
Reverse polarity protection 51
Configuring the RT 53
Overview 53
Selecting the operating language 54
Navigating through NAVconfig 54
Product selection 54
Reading configuration 55
GNSS Selection 57
Orientation 57
Get improved settings 59
Primary antenna 61
Secondary antenna 63
Advanced slip 64

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Options 66
Vehicle starts 67
Vibration 67
GNSS environment 68
Differential correction 68
SBAS 70
DGNSS service 70
CAN 71
Heading lock 77
Garage mode 78
Initialisation speed 78
Displace output 78
Distance output 79
Analogue output 79
Acceleration filter 80
Wheel speed input 81
Local co-ordinates 83
Serial 1 output 84
Ethernet output 86
Steering robot IP 88
Output smoothing 88
Slip points 89
GNSS control 90
Surface tilt 92
Coordinate system 93
Advanced 94
Committing the configuration to the RT 95
Saving the configuration and finishing 96
Setting up the base station 97
Using the RT-Base S 97
Initialisation process 98
Real-time outputs 98
Warm-up period 99
Post-processing data 103
Laboratory testing 104
Accelerometer test procedure 104
Gyro test procedure 104
Testing the internal GNSS and other circuitry 106

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Using the orientation measurements 107
Operating principles 108
Internal components 108
Strapdown navigator 109
Kalman filter 110
CAN messages and signals 112
Termination resistor 112
CAN-DB file 112
CAN bus messages 112
Table heading definitions 114
Signals 115
Revision history 131
Drawing list 132

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Oxford Technical Solutions
Introduction
The RT family of inertial navigation system (INS) devices, are instruments for making
precision measurements of motion in real-time.
There are three divisions within the RT family; RT2000s, RT3000s and RT4000s—and
each division contains a number of different models. The difference between the
divisions is described in more detail in the “RT product family” section on page 13.
From June 2014, all products in the RT family—except RT2500s, will be built to a new
specification called v2. These v2 devices can achieve 1 cm RTK accuracy in both real-
time and post-process, instead of the 2 cm accuracy of previous models. While the
existing model names have been kept for continuity, a v2 suffix denotes devices built to
the new specification. The only significant change is for customers using a DGNSS
subscription service, as v2 devices only support TerraStar, not OmniSTAR.
To obtain high-precision measurements, the RT uses mathematical algorithms developed
for use in fighter aircraft navigation systems. An inertial sensor block with three
accelerometers and three gyros (angular rate sensors) is used to compute all the outputs.
A WGS 84 modelled strapdown navigator algorithm compensates for earth curvature,
rotation and Coriolis accelerations, while measurements from high-grade kinematic
GNSS receivers update the position and velocity navigated by the inertial sensors. This
innovative approach gives the RT several distinct advantages over systems that only use
GNSS:
•The RT has a high (100 Hz or 250 Hz) update rate and a wide bandwidth.
•The outputs are available with very low, 3.5 ms latency.
•All outputs remain available continuously during GNSS blackouts when, for
example, the vehicle drives under a bridge.
•The RT recognises jumps in GNSS position and ignores them.
•The position and velocity measurements the GNSS makes are smoothed to reduce
the high-frequency noise.
•The RT makes many measurements GNSS cannot, for example acceleration, angular
rate, heading, pitch and roll.
An RT system processes data in real-time. The real-time results are output via an RS232
serial port, over 10/100 Base-T Ethernet using a UDP broadcast and on CAN bus.
Outputs are time-stamped and refer to GPS time; a 1PPS timing sync can be used to give
very accurate timing synchronisation between systems. The inertial measurements are
synchronised to the GPS clock.

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Internal data logging enables the data to be reprocessed post-mission. Data can be
collected in the unit, downloaded using “ftp”, processed on a PC and viewed using the
customer’s software.
Easy operation
There is minimal configuration required to use the system. The configuration can be
saved to the RT so it can operate autonomously without user intervention. A lot of work
has been put into the initialisation of the inertial algorithms so the RT can reliably start
to navigate in the vast majority of situations.
The single unit contains inertial sensors, GNSS receiver, data storage and CPU. One or
two antennas need to be mounted outside the vehicle where they have a clear view of the
sky. A 10–25 V dc power supply can be obtained from most vehicles. A laptop computer
allows real-time viewing of the results.
Self-correcting
Unlike conventional inertial navigation systems, the RT uses GNSS to correct all its
measurements. GNSS makes measurements of position, velocity and (for dual antenna
systems) heading. Using these measurements, the RT is able to keep other quantities,
such as roll and pitch accurate. Tight coupling of the GNSS and inertial measurements
means the raw GNSS data can also be used. There is no drift from the RT in any of the
measurements while GNSS is present.
Interchangeable
All RT products have identical output capabilities and are interchangeable. The serial
port, Ethernet and CAN bus are the same on all the systems including the data formats.
The connectors on the RT2000 products are different but can usually be interfaced.
Advanced processing
In poor GNSS environments, drift times can be halved by using the combined results of
processing forwards and backwards in time. Our proprietary gx/ix processing engine can
further improve performance with single satellite aiding algorithms and tight coupling of
the inertial and GNSS measurements, meaning position updates even with fewer than
four satellites in view

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Oxford Technical Solutions
Related documents
This manual covers the installation and operation of RT systems, but it is beyond its
scope to provide details on service or repair. Contact OxTS support or your local
representative for customer service related inquiries.
Additional manuals provide further information on some of the software and
communication types mentioned in this manual. Table 1 lists related manuals; all of
which can be downloaded from the support website (https://support.oxts.com).
Table 1. Supplementary manuals
Manual Description
NAVdisplay
Manual
NAVdisplay can be used to view INS measurements on a PC in real-time or by
replaying existing data files. It provides a useful method of checking the status of
your INS
NAVgraph
Manual NAVgraph is used to plot, analyse and export measurement data once processed
NCOM Manual NCOM is a propriety format developed by OxTS that is used in our products. The
NCOM manual provides information about decoding and using the NCOM format
NCOM C Code
Drivers
This ZIP file contains a collection of C functions that can be used to decode the
binary protocols from the INS
NMEA 0183
Description NMEA description manual for the NMEA outputs found on our INS products
NAVsolve
Manual
NAVsolve can download data from an INS and process it using a number different
technologies to extract the best possible accuracy. DGNSS corrections can also be
applied
RT-Base S Explains how to set-up and use the RT-Base S base station to achieve RTK integer
operation mode
RT Quick-start
guide Short guide to quickly set-up and start using an RT.

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RT product family
The RT product family is split into three divisions—all based on similar technology, and
within each division, there are a number of models serving different accuracy
requirements.
The RT family is split into the following divisions:
•RT2000s
Fitted with lower-cost GNSS receivers. Available in single and dual antenna models
and can be GLONASS enabled. 100 Hz and 250 Hz versions.
•RT3000s
Survey grade GNSS receivers provide high-precision position and velocity
measurements even in high multipath environments. Can be GLONASS enabled.
Single and dual antenna models are available. Update rates up to 100 Hz.
•RT4000s
These products are identical to the RT3000 series, but have an update rate of up to
250 Hz.
The models contained within each division are listed in the “Specification” section on
page 20.
Single antenna
An advanced algorithm in the RT software means most road vehicle customers are able
to use a single antenna system. The Heading lock and Advanced slip features allow RT
devices to maintain an accurate heading while stationary and while driving with low
vehicle dynamics.
Dual antenna
Dual antenna systems provide high accuracy heading information and almost constant
heading performance under all conditions. Single antenna systems can experience
reduced heading accuracy on aircraft, boats or in low speed land vehicles.
For aircraft or marine applications, or road vehicle applications on low-friction surfaces
(e.g. ice), a dual antenna system is recommended to maintain high accuracy heading.
Advanced processing in the RT allows relock to occur after five seconds of a sky-
obstruction—unlike GNSS-only systems which can take several minutes; in this time the
RT’s heading will not have significantly degraded. The fast relock time is made possible
because the RT’s own heading is used to resolve the ambiguities in the GNSS
measurements. Resolution of these ambiguities is what normally takes several minutes.

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Oxford Technical Solutions
The heading software in the RT enables significantly better performance and coverage
compared to GNSS-only solutions.
GLONASS
GLONASS capability adds the ability to utilise the Russian satellite constellation
GLONASS as well as the American constellation GPS. This means an extra 24 satellites
are available for the RT to lock on to and obtain position and velocity updates from.
In open sky conditions, the addition of GLONASS capability is of little benefit as the
GPS signals are unlikely to be interrupted and full accuracy can be achieved almost 100%
of the time. However, in open-road testing situations there are likely to be bridges, trees,
and tall buildings that can block the view of satellites or cause multipath effect errors. In
these situations, GPS and GLONASS receivers are able to maintain 1 cm accurate RTK
positioning mode at times when GPS-only receivers are not. They are also able to re-
establish RTK lock and resolve its ambiguities after an obstruction faster.
Note: at this time, gx/ix processing does not support GLONASS. To take full advantage
of GLONASS capability, standard processing must be used.
250 Hz
1. All product divisions have the option of coming with a 250 Hz version of the inertial
measurement unit (IMU). The IMUs used in 100 Hz and 250 Hz products are
essentially the same, both with a fundamental sampling frequency of 1000 Hz. The
difference is the 3D filter used to integrate the accelerations and angular rates has a
smaller time step in the 250 Hz models, allowing a higher update rate.
2. However, because of the smaller time step, measurements that depend on angular
acceleration are typically noisier on the 250 Hz products. The noise can be managed
by filtering the data to limit the bandwidth.
Satellite differential corrections
To improve the positioning accuracy of standard GNSS, two satellite-based differential
correction services are available. These are SBAS and TerraStar.
Services such as WAAS and EGNOS, are wide-area differential corrections provided for
free. They can provide an accuracy of better than 1 m CEP. WAAS is available in North
America; EGNOS is available in Europe; MSAS is available in Japan; GAGAN is
available in India; SDCM is available in Russia. Other parts of the world are not covered
and cannot use this service.
TerraStar is a subscription service. RT systems that have TerraStar capability include the
necessary hardware to receive corrections. It is necessary to pay a license fee to activate

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these corrections. Capable RT system will use the TERRASTAR-D service which can
provide better than 10 cm position accuracy. TerraStar is available on all continents.
Marine versions also exist.
For more information, see TerraStar’s web site: http://www.terrastar.net/.

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Scope of delivery
RT products are supplied complete with cables, GNSS antennas, software and manuals.
As standard, magnetic mount antennas are provided but other antenna types are available;
please enquire for more details.
RT2000 system components
Table 2 lists all items that are delivered with each RT2000 model.
Table 2. Summary of RT2000 system components
Description RT2500
RT2500-250
RT2502
RT2502-250
RT2002
RT2002G
RT2002-250
RT2002G-250
RT2000 system unit 
Power cable 77C0002B 
GNSS antenna AT575-70 × 2
GNSS antenna G5Ant-2AMNS1 
5 m GNSS antenna cable 
Radio modem cable 14C0062B 
Ethernet cable (cross-over) 
USB memory stick with software 
User manual 
Calibration certificate 
The RT2000 product requires the correct differential corrections in order to work to full
specification. Differential corrections can be supplied by an RT-Base, GPS-Base, NTRIP
or other suitable differential correction source.
In addition to the components supplied, the user will require a laptop computer or other
logging system.

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RT3000 system components
Table 3 lists all the items that are delivered with each RT3000 model.
Table 3. Summary of RT3000 system components
Description RT3100 RT3102 RT3100G RT3102G RT3002
RT3002G
RT3003
RT3003G
RT3000 system
unit

User cable
(14C0038B)
     
GNSS antenna
AT575–70
× 2
GNSS antenna
G5Ant-
2AMNS1
× 2 × 2
5 m GNSS
antenna cable
× 2 × 2
USB memory
stick (manual &
software)

Ethernet cable 
    
Ethernet
crossover
coupler

User manual 
Calibration
certificate

The RT3000 products require the correct differential corrections in order to work to their
full specification. Differential corrections can be supplied by an RT-Base S, GPS-Base,
NTRIP or other suitable differential correction source.
In addition to the components supplied the user will require a laptop computer or
alternative logging system.

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RT4000 system components
Table 4 lists all the items that are delivered with each RT4000 model.
Table 4. Summary of RT4000 system components
Description RT4100 RT4102 RT4100G RT4102G RT4002
RT4002G
RT4003
RT4003G
RT4000 system
unit

User cable
(14C0038B)

GNSS antenna
AT575–70
× 2
GNSS antenna
G5Ant-
2AMNS1
× 2 × 2
GNSS antenna
cable (5 m)
× 2 × 2
USB memory
stick (manual &
software)

Ethernet cable 
Ethernet
crossover
coupler

User manual 
Calibration
certificate

The RT4000 products require the correct differential corrections in order to work to their
full specification. Differential corrections can be supplied by an RT-Base, GPS-Base,
NTRIP or other suitable differential correction source.
In addition to the components supplied the user will also require a laptop computer or
alternative logging system.

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Figure 1. Typical RT system and cables in transit case.

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Oxford Technical Solutions
Specification
Specifications for RT products can be found in Table 5, Table 6, and Table 7. These
specifications are listed for operation of the system under the following conditions:
•After a warm-up period of 15 minutes’ continuous operation.
•Open-sky environment, free from cover by trees, bridges, buildings or other
obstructions. The vehicle must have remained in open-sky for at least five minutes
for full accuracy.
•The vehicle must exhibit some motion behaviour. Acceleration of the unit in different
directions is required so the Kalman filter can estimate any errors in the sensors.
Without this estimation, some of the specifications degrade.
•The distance from the RT measurement point to the primary GNSS antenna must be
known by the system to a precision of five millimetres or better. The vibration of the
system relative to the vehicle cannot allow this to change by more than five
millimetres. The system will estimate this value itself in dynamic conditions.
•For dual antenna systems, the system must know the relative orientation of the two
antennas to 0.05° or better. The system will estimate this value itself under dynamic
conditions.
•For single antenna systems, the heading accuracy is only achieved under dynamic
conditions. Under benign conditions, such as motorway driving, the performance will
degrade. The performance is undefined when stationary for prolonged periods of
time.
Optionally, extended measurement ranges covering 30 gacceleration and 300°/s angular
rate may be requested. The specification using the extended measurement range sensors
can be marginally worse than those listed here.
Table 5. RT2000 performance specification
Parameter RT2500 /
RT2500–
250
RT2502 /
RT2502–250
RT2002 v2/
RT2002–250
v2
RT2002G v2 /
RT2002G-250
v2
Positioning GPS L1 GPS L1 GPS L1, L2 GPS L1, L2
GLONASS L1,
L2