Sokkia Axis 3 User manual

 Axis 3 TM
Operations Manual
Part Number 750-1-0060 Rev 2
GPS Receiver System

Copyright Notice
Copyright © 2000 POINT, Inc. All rights reserved.
No part of this publication or the equipment described in it may be
reproduced, translated, stored in a retrieval system, or transmitted in any
form or by any means, electronic, mechanical photocopying, recording, or
otherwise, without prior written permission of POINT, Inc. Your rights with
regard to this publication and the equipment are subject to the restrictions
and limitations imposed by the copyright laws of the United States of
America (“U.S.A.”) and/or the jurisdiction in which you are located.
Trademark Notice
Sokkia is a trademark of Sokkia Co. Ltd.
All other product and brand names are trademarks or registered trademarks
of their respective holders.
FCC Notice
The equipment described in this manual has been tested pursuant to Part 15
of the FCC Rules and found to comply with the limits for a Class A digital
device for use in commercial business, and industrial environments.
Operation is subject to the following two conditions: (1) this device may not
cause harmful interference, and (2) this device must accept any interference
received, including interference that may cause undesired operation. These
limits are designed to provide reasonable protection against harmful
interference when the equipment is operated in a commercial environment.
The equipment generates, uses, and can radiate radio frequency energy and,
if not installed and used in accordance with the instruction manual, may
cause harmful interference to radio and television reception. Operation of
this equipment in a residential area is likely to cause harmful interference in
which case the user will be required to correct the interference at his own
expense.
If this equipment does cause interference to radio or television reception,
which can be determined by turning the equipment off and on, you can try to
correct the interference by one or more of the following measures:
• Reorient the receiving antenna.
• Relocate the receiver relative to the equipment which it interferes.
• Power the equipment from a different AC receptacle so that this
equipment and the interfered equipment are on different branch circuits.
If necessary, contact our customer service department or an authorized
representative for additional advice.
750-1-0060 Rev 2 October 16, 2000
POINT, Inc.—Advanced Measurement Solutions from Sokkia and NovAtel

Axis 3i
Contents
Chapter 1 Welcome................................................... 1
1.1 Ports and Icons ............................................................... 1
1.2 Notes, Cautions, and Warnings................................... 1
1.3 Obtaining Technical Support ....................................... 2
Chapter 2 Introduction.............................................. 5
2.1 Understanding GPS....................................................... 5
2.1.1 How it Works ...................................................... 5
2.1.2 GPS Services ........................................................ 6
2.1.3 DGPS Format, GPS Standard............................ 6
2.2 Differential GPS.............................................................. 7
2.2.1 How it Works ...................................................... 7
2.2.2 Real-Time DGPS.................................................. 7
2.3 OmniSTAR Worldwide DGPS Service ....................... 7
2.3.1 OmniSTAR signal information......................... 8
2.3.2 OmniSTAR Reception and DGPS..................... 8
2.3.2.1 Activating the OmniSTAR Service.............9
2.3.2.2 Over-Air Subscription Activation.............10
2.4 Radio Beacon Service................................................... 11
2.4.1 Radiobeacon Range .......................................... 11
2.4.2 Radiobeacon Messages..................................... 12
2.4.3 Radiobeacon Coverage..................................... 13
2.5 Radio Beacon Position Accuracy ............................... 14
2.5.1 Proximity............................................................ 14
2.5.2 Latency ............................................................... 15
2.5.3 Ionospheric Errors ............................................ 15
2.5.4 Satellites Visible ................................................ 16
2.5.5 MultiPath ........................................................... 16
2.6 Using WAAS................................................................. 16

ii Axis 3
Contents
2.6.1 Wide Area Augmentation System .....................
(WAAS)16
2.6.2 WAAS reception and DGPS ............................17
2.7 Axis 3Receiver..............................................................17
2.8 Axis 3Antenna..............................................................18
Chapter 3 Receiver Set Up......................................19
3.1 Receiver Layout and Connections .............................19
3.1.1 Connecting Cables ............................................20
3.1.2 Communication.................................................21
3.2 Installing the Axis 3Receiver......................................22
3.2.1 Environmental Considerations .......................22
3.2.2 Connecting Power.............................................22
3.3 Axis 3Antenna Guidelines..........................................22
3.3.1 Placing Antenna for Optimal Reception........23
3.3.2 Routing and Securing the Antenna Cable.....23
3.3.3 Connecting the Axis 3 Antenna.......................24
3.4 Installing the Data Collector.......................................24
3.5 Preparing for Operation..............................................24
Chapter 4 Axis 3Operation......................................27
4.1 Locating Satellites.........................................................27
4.2 Interpreting LED Indicators........................................28
4.2.1 Other LED Conditions (OmniSTAR)..............29
4.3 Understanding Settings...............................................29
4.3.1 Default Configuration ......................................30
4.4 Beacon Tune Mode.......................................................30
4.4.1 Using ABS Mode...............................................31
4.4.1.1 ABS Global Search ......................................31
4.4.1.2 ABS Background Search.............................31
4.4.2 Using Manual Mode.........................................32
4.5 Beacon Performance - SNR Reading .........................32
4.6 DGPS Performance.......................................................33

Contents
Axis 3iii
Appendix A Troubleshooting.....................................35
Appendix B Specifications.........................................36
Appendix C Frequently Asked Questions ................41

Axis 3™ 1
Chapter 1 Welcome
Welcome to the Axis 3Operations Manual and congratulations
on purchasing this high performance GPS product from Sokkia.
The purpose of this manual is to familiarize you with the
proper installation, configuration, and operation of your new
receiver. The Axis 3is a high performance 12-channel GPS
receiver with flexible real-time solutions. This integrated
product is designed to provide positioning by using corrections
from its internal beacon, differential satellite and WAAS sensors
to function in a wide array of applications and environments.
Compact, lightweight, yet rugged, the Axis 3receiver will
provide you with years of reliable operation.
1.1 Ports and Icons
This icon is the symbol for power and identifies the power
port, which is located on the rear panel of the Axis
receiver. The power port is also referred to in this docu
ment as PWR.
This icon is the symbol for communications and identifies
the communications port, which is located on the rear
panel of the Axis receiver. The communications port is
also referred to in this document as COM.
This icon is the symbol for antenna and identifies the
antenna port, which is located on the rear panel of the
Axis receiver. The antenna port is also referred to in this
document as RF.
1.2 Notes, Cautions, and Warnings
Notes, Cautions, and Warnings stress important information

2Axis
3™
Chapter 1 Welcome
regarding the installation, configuration, and operation of the
Axis 3receiver.
*Note: Notes outline important information of a general
nature.
1.3 Obtaining Technical Support
When contacting customer support, please ensure the following
information is available: the product model, serial number and
a concise description of the problem.
CAUTION
Cautions inform of possible sources of difficulty or situations that may cause
damage to the product.
WARNING
Warnings inform of situations that may cause you harm.

Welcome Chapter 1
Axis 3™3
Canada
Sokkia Corp.
1050 Stacey Court
Mississauga, Ontario
L4W 2X8
Phone [phone]
Fax [phone]
Australia
Sokkia Pty. Ltd.
Rydalmere Metro Centre
Unit 29,38-46 South Street
Rydalmere NSW 2116
Australia
Phone [phone]
Fax [phone]
U.K.
Sokkia Ltd.
Datum House, Electra Way
Crewe Business Park
Crewe, Cheshire, CW1 6ZT
United Kingdom
Phone [phone]
Fax [phone]
Europe
Sokkia B.V.
Businesspark De Vaart
Damsluisweg 1, 1332 EA Almere
P.O. Box 1292, 1300 BG Almere
The Netherlands
Phone [phone]
Fax [phone]
New Zealand
Sokkia New Zealand
20 Constellation Drive
Mairangi Bay, C.P.O. Box 4464,
Auckland 10
New Zealand
Phone [phone]
Fax [phone]
USA
Sokkia Corporation
16900 W. 118th Terrace
P.O. Box 726
Olathe, KS 66061
Phone [phone]
Fax [phone]
Asia
Sokkia Singapore Pte. Ltd.
401 Commonwealth Drive
#06-01 Haw Par Technocentre
Singapore 149598
Phone [phone]
Fax [phone]
Africa
Sokkia RSA Pty. Ltd.
P.O. Box 7998
Centurion, 0046
Republic of South Africa
Phone [phone]
Fax [phone]
Central & South America
Sokkia Central & South America
1200 N.W. 78 Avenue
Suite 109
Miami, FL
USA 33126
Phone [phone]
Fax [phone]

Welcome Chapter 1
Axis 3™5

Axis 3™5
Chapter 2 Introduction
This chapter provides a brief overview of the Global
Positioning System (GPS), differential GPS (DGPS), beacon and
satellite differential and a description of the Axis 3receiver,
antenna, and accessories.
2.1 Understanding GPS
The United States Department of Defense (DoD) operates a
reliable, 24 hour, all-weather GPS.
Navstar, the original name given to this geographic positioning
and navigation tool, includes a constellation of 24 satellites
(plus active spares) orbiting the Earth at an altitude of
approximately 22,000 km.
*Note: Selective Availability, SA, was turned off in May 2000.
The initial intent of the Department of Defense was to have
the ability to degrade the quality of the GPS signal for all
non-military users. The resulting positioning accuracy with
SA on is from a few meters to 100 meters, however with SA
off the positioning accuracy is approximately two to five
meters. If there is an immediate danger perceived to the
USA, SA may be turned on without review.
2.1.1 How it Works
GPS satellites transmit coded information to GPS users at UHF
(1.575 GHz) frequencies that allows user equipment to calculate
a range to each satellite. GPS is essentially a timing system -
ranges are calculated by timing how long it takes for the GPS
signal to reach the user’s GPS antenna.

6Axis
3™
Chapter 2 Introduction
To calculate a geographic position, the GPS receiver uses a
complex algorithm incorporating satellite coordinates and
ranges to each satellite. Reception of any four or more of these
signals allows a GPS receiver to compute 3D coordinates.
Tracking of only three satellites reduces the position fix to 2D
coordinates (horizontal with fixed vertical).
2.1.2 GPS Services
The positioning accuracy offered by GPS varies depending
upon the type of service and equipment available. For security
reasons, two GPS services exist: the Standard Positioning
Service (SPS) and the Precise Positioning Service (PPS). The US
DoD reserves the PPS for use by its personnel and authorized
partners. The DoD provides the SPS free of charge, worldwide,
to all civilian users.
For many positioning and navigation applications, stand-alone
or autonomous accuracy is insufficient, and differential
positioning techniques must be employed.
2.1.3 DGPS Format, GPS Standard
For manufacturers of GPS equipment, commonality is essential
to maximize the utility and compatibility of a product. The
governing standard associated with GPS is the Interface
Control Document, ICD-GPS-200, maintained by the US DoD.
This document provides the message and signal structure
information required to access GPS.
Like GPS, DGPS data and broadcast standards exist to ensure
compatibility between DGPS networks and associated
hardware and software. The Radio Technical Commission for
Maritime Services Special Committee 104 has developed the
primary DGPS standard associated with radiobeacon DGPS,
designated RTCM SC-104 V2.2.

Introduction Chapter 2
Axis 3™7
2.2 Differential GPS
The purpose of DGPS is to remove the effects of atmospheric
errors, timing errors, and satellite orbit errors, while enhancing
system integrity.
2.2.1 How it Works
DGPS involves setting up a reference GPS receiver at a point of
known coordinates. This receiver makes distance
measurements, in real-time, to each of the GPS satellites. The
measured ranges include the errors present in the system. The
base station receiver calculates what the true range should be,
without errors, knowing its coordinates and those of each
satellite. The difference between the known and measured
range for each satellite is the range error. This error is the
amount that needs to be removed from each satellite distance
measurement in order to correct for errors present in the
system.
2.2.2 Real-Time DGPS
The base station transmits the range error corrections to remote
receivers in real-time. The remote receiver corrects its satellite
range measurements using these differential corrections,
yielding a much more accurate position. This is the
predominant DGPS strategy used for a majority of real-time
applications. Positioning using corrections generated by DGPS
radiobeacons will provide a horizontal accuracy of one to five
meters with a 95% confidence.
2.3 OmniSTAR Worldwide DGPS Service
OmniSTARTM is a worldwide terrestrial service that provides
DGPS corrections to subscribers of the system through a
geostationary satellite signal.

8Axis
3™
Chapter 2 Introduction
2.3.1 OmniSTAR signal information
The OmniSTAR satellite correction is a line-of-sight UHF signal
similar to the GPS signal. Various L-Band communications
satellites are used for transmitting the correction data to
OmniSTAR users around the world. The OmniSTAR signal can
be used where beacon signals are not available.
The OmniSTAR service uses geostationary satellites (satellites
that remain stationary in relation to the earth) for
communication. The elevation angle to these satellites is
dependent upon latitude. OmniSTAR provides differential
coverage over most of the land areas of the globe, with the
exception of some areas beyond 60 degrees South Latitude.
However, even within the coverage areas, the user must have a
clear line-of-sight to the satellite.
2.3.2 OmniSTAR Reception and DGPS
The OmniSTAR network functions as a wide-area DGPS
service. The information broadcast by the service is based on a
network of strategic reference stations. The reference stations
communicate GPS correction data to control centers where it is
decoded, checked, and repackaged into a proprietary format for
transmission to a geostationary L-band communications
satellite. This correction data is rebroadcast to the Earth over a
large area where an L-band differential receiver demodulates
the data.
The Axis 3receiver will process corrections from the wide-area
signal specific to your location. The resulting corrections are
similar to those calculated if a reference station was set up at
your location. This type of solution ensures a consistent level of
accuracy across the entire coverage area.
The OmniSTAR signal is a proprietary wide-area signal (not
RTCM SC-104) with specialized geographically independent
formats. Positioning accuracy will not degrade based on the
distance to a base station. The data is composed of information

Introduction Chapter 2
Axis 3™9
from an entire network as opposed to a single base station.
When the signal is demodulated by a DGPS receiver, it is
converted to a local-area format (standard RTCM SC-104,
message Type 1) for input.
The Axis 3 L-Band receiver uses a feature called a Virtual Base
Station (VBS) when processing the OmniSTAR wide-area
signal. The resulting corrections are those that would be
applied if a reference station were set up at your present
location. This provides consistent accuracy levels across the
coverage area.
*Note: The GPS receiver inside the Axis 3provides position
information to the L-Band receiver for VBS calculations.
2.3.2.1 Activating the OmniSTAR Service
To use OmniSTAR, you must know your receiver’s internal L-
band receiver number. This number can be found on the silver
tag located on the bottom of the receiver.
You can contact the OmniSTAR office closest to your location to
receive a subscription.
Location Phone Number Fax Number
North America [phone] [phone]
Europe/North America [phone] [phone]
Asia, Australia, New
Zealand, South Africa [phone] [phone]
Central American,
South America [phone] [phone]

10 Axis 3™
Chapter 2 Introduction
2.3.2.2 Over-Air Subscription Activation
After you contact OmniSTAR, your subscription can be
activated on your Axis 3receiver over the air. The internal
DGPS receiver will automatically lock on to the signal even if
your subscription has not been activated, however it is of no
use to you until your subscription is activated.
When you power on the receiver, you must have the antenna in
a location with an unobstructed view of the sky. The
subscription activation will be transmitted over the air and
received by the internal L-band DGPS receiver.
To confirm you have a valid and active OmniSTAR
subscription, refer to your data collection software reference
manual.

Introduction Chapter 2
Axis 3™11
*Note: Please see the service contract included with the Axis
3 receiver system.
2.4 Radio Beacon Service
The Axis 3receiver is able to use differential corrections
received through the internal beacon receiver, operating
seamlessly with DGPS beacon networks throughout the world.
The receiver uses signals from the United States Coast Guard
(USCG), Canadian and all International Association of
Lighthouse Authorities (IALA) stations to provide free
differential corrections.
*Note: The Axis 3 default operation mode is beacon.
2.4.1 Radiobeacon Range
The broadcasting range of a 300 kHz beacon is dependent upon
a number of factors including transmission power, free space
loss, ionospheric state, surface conductivity, ambient noise, and
atmospheric losses.
The strength of a signal decreases with distance from the
transmitting station, due in large part to spreading loss. This
loss is a result of the signal’s power being distributed over an
increasing surface area as the signal radiates away from the
transmitting antenna.
The expected range of a broadcast also depends upon the
conductivity of the surface over which it travels. A signal will
propagate further over a surface with high conductivity than
over a surface with low conductivity. Lower conductivity
surfaces such as dry, infertile soil, absorb the power of the
transmission more than higher conductivity surfaces, such as
sea water or arable land.

12 Axis 3™
Chapter 2 Introduction
A radiobeacon transmission has three components: a direct line
of sight wave, a ground wave, and a sky wave. The line of sight
wave is not significant beyond visual range of the transmitting
tower, and does not have a substantial impact upon signal
reception.
The ground wave portion of the signal propagates along the
surface of the earth, losing strength due to spreading loss,
atmospheric refraction and diffraction, and attenuation by the
surface over which it travels (dependent upon conductivity).
The portion of the beacon signal broadcast skyward is known
as the sky wave. Depending on its reflectance, the sky wave
may bounce off the ionosphere and back to Earth causing
reception of the ground wave to fade. Fading occurs when the
ground and sky waves interfere with each other. The effect of
fading is that reception may fade in and out. However, this
problem usually occurs in the evening when the ionosphere
becomes more reflective and usually on the edge of coverage
areas. Fading is not usually an issue with overlapping coverage
areas of beacons and their large overall range.
Atmospheric attenuation plays a minor part in signal
transmission range, as it absorbs and scatters the signal. This
type of loss is the least significant of those described.
2.4.2 Radiobeacon Messages
Various sources of noise affect beacon reception, and include:
•Engine noise
•Alternator noise
•Noise from Power lines
•DC to AC inverting equipment
•Electric devices such as CRT’s electric motors, and
solenoids
Noise generated by this type of equipment can mask the beacon
signal, reducing or impairing reception.

Introduction Chapter 2
Axis 3™13
2.4.3 Radiobeacon Coverage
Figure 1 shows the approximate radiobeacon coverage
throughout the world. In this figure, light shaded regions note
current coverage, with beacon stations symbolized as white
circles.
Figure 1: World DGPS Radiobeacon Coverage—April 1999
The world beacon networks continue to expand and coverage
areas are growing. The online listing provides the following
information about each beacon:
•Station name
•Frequency
•MSK rate
•Location
•Transmitting ID
•Reference station ID
•Field Strength
•Operating notes