Ag Leader GPS 5100 User Guide

GPS 5100 Receiver

User Guide

A

Version 1.00

Revision A

Part Number 55510-45-ENG

January 2005

Contact Information

Ag Leader Technology
2202 South Riverside Drive
P.O.Box 2348
Ames, Iowa 50010

[phone] Phone
[e-mail]

www.agleader.com

Copyright and Trademarks

© 2004-2005, Trimble Navigation Limited. All rights
reserved.

Trimble and AgGPS are trademarks of Trimble
Navigation Limited, registered in the United States
Patent and Trademark Office and other countries.
Autopilot, EVEREST, MS750, and SiteNet are
trademarks of Trimble Navigation Limited.

Microsoft and ActiveSync are either registered
trademarks or trademarks of Microsoft Corporation in
the United States and/or other countries. All other
trademarks are the property of their respective owners.

Release Notice

This is the January 2005 release (Revision A) of the GPS
5100 Receiver User Guide, part number 55510-45-ENG.

It applies to version 1.00 of the GPS 5100 receiver.

The following limited warranties give you specific legal
rights. You may have others, which vary from
state/jurisdiction to state/jurisdiction.

Hardware Limited Warranty

Ag Leader warrants that this hardware product (the
“Product”) will perform substantially in accordance with
published specifications and be substantially free of
defects in material and workmanship for a period of two
(2) years starting from the date of delivery. The warranty
set forth in this paragraph shall not apply to software
products.

Software License, Limited Warranty

This Ag Leader software product, whether provided as a
stand-alone computer software product, built into
hardware circuitry as firmware, embedded in flash
memory, or stored on magnetic or other media, (the
“Software”) is licensed and not sold, and its use is
governed by the terms of the relevant End User License
Agreement (“EULA”) included with the Software. In the
absence of a separate EULA included with the Software
providing different limited warranty terms, exclusions
and limitations, the following terms and conditions shall
apply. Ag Leader warrants that this Ag Leader
Technology Software product will substantially conform
to Ag Leader’s applicable published specifications for
the Software for a period of ninety (90) days, starting
from the date of delivery.

Warranty Remedies

Ag Leader's sole liability and your exclusive remedy
under the warranties set forth above shall be, at Ag
Leader’s option, to repair or replace any Product or
Software that fails to conform to such warranty
(“Nonconforming Product”) or refund the purchase price
paid by you for any such Nonconforming Product, upon
your return of any Nonconforming Product to Ag Leader
in accordance with Ag Leader’s standard return material
authorization procedures.

Warranty Exclusions and Disclaimer

These warranties shall be applied only in the event and
to the extent that (i) the Products and Software are
properly and correctly installed, configured, interfaced,
maintained, stored, and operated in accordance with Ag
Leader's relevant operator's manual and specifications,
and; (ii) the Products and Software are not modified or
misused. The preceding warranties shall not apply to,
and Ag Leader shall not be responsible for defects or
performance problems resulting from (i) the
combination or utilization of the Product or Software
with hardware or software products, information, data,
systems, interfaces or devices not made, supplied or
specified by Ag Leader; (ii) the operation of the Product
or Software under any specification other than, or in
addition to, Ag Leader's standard specifications for its
products; (iii) the unauthorized, installation,
modification
damage caused by accident, lightning or other electrical
discharge, fresh or salt water immersion or spray; or (v)
normal wear and tear on consumable parts (e.g.,
batteries). Ag Leader does not warrant or guarantee the

, or use of the Product or Software; (iv)

results obtained through the use of the Product.

THE WARRANTIES ABOVE STATE AG LEADER'S
ENTIRE LIABILITY, AND YOUR EXCLUSIVE
REMEDIES, RELATING TO PERFORMANCE OF THE
PRODUCTS AND SOFTWARE. EXCEPT AS OTHERWISE
EXPRESSLY PROVIDED HEREIN, THE PRODUCTS,
SOFTWARE, AND ACCOMPANYING
DOCUMENTATION AND MATERIALS ARE PROVIDED

AS-IS” AND WITHOUT EXPRESS OR IMPLIED

“

WARRANTY OF ANY KIND BY EITHER AG LEADER
TECHNOLOGY OR ANYONE WHO HAS BEEN
INVOLVED IN ITS CREATION, PRODUCTION,
INSTALLATION, OR DISTRIBUTION INCLUDING, BUT
NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE, TITLE, AND
NONINFRINGEMENT. THE STATED EXPRESS
WARRANTIES ARE IN LIEU OF ALL OBLIGATIONS OR
LIABILITIES ON THE PART OF AG LEADER ARISING
OUT OF, OR IN CONNECTION WITH, ANY PRODUCTS
OR SOFTWARE. SOME STATES AND JURISDICTIONS
DO NOT ALLOW LIMITATIONS ON DURATION OR
THE EXCLUSION OF AN IMPLIED WARRANTY, SO
THE ABOVE LIMITATION MAY NOT APPLY TO YOU.

A

G LEADER TECHNOLOGY IS NOT RESPONSIBLE

ii GPS 5100 Receiver User Guide

FOR THE OPERATION OR FAILURE OF OPERATION OF
GPS SATELLITES OR THE AVAILABILITY OF GPS
SATELLITE SIGNALS.

Limitation of Liability

A

G LEADER’S ENTIRE LIABILITY UNDER ANY
PROVISION HEREIN SHALL BE LIMITED TO THE
AMOUNT PAID BY YOU FOR THE PRODUCT OR
SOFTWARE LICENSE. TO THE MAXIMUM EXTENT
PERMITTED BY APPLICABLE LAW, IN NO EVENT
SHALL AG LEADER OR ITS SUPPLIERS BE LIABLE
FOR ANY INDIRECT, SPECIAL, INCIDENTAL OR
CONSEQUENTIAL DAMAGES WHATSOEVER UNDER
ANY CIRCUMSTANCE OR LEGAL THEORY RELATING
IN ANY WAY TO THE PRODUCTS, SOFTWARE AND
ACCOMPANYING DOCUMENTATION AND
MATERIALS, (INCLUDING, WITHOUT LIMITATION,
DAMAGES FOR LOSS OF BUSINESS PROFITS,
BUSINESS INTERRUPTION, LOSS OF BUSINESS
INFORMATION, OR ANY OTHER PECUNIARY LOSS),
REGARDLESS WHETHER AG LEADER HAS BEEN
ADVISED OF THE POSSIBILITY OF ANY SUCH LOSS
AND REGARDLESS OF THE COURSE OF DEALING
WHICH DEVELOPS OR HAS DEVELOPED BETWEEN
YOU AND AG LEADER. BECAUSE SOME STATES AND
JURISDICTIONS DO NOT ALLOW THE EXCLUSION OR
LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR
INCIDENTAL DAMAGES, THE ABOVE LIMITATION
MAY NOT APPLY TO YOU.

NOTE: THE ABOVE LIMITED WARRANTY
PROVISIONS MAY NOT APPLY TO PRODUCTS OR
SOFTWARE PURCHASED IN THE EUROPEAN UNION.
PLEASE CONTACT YOUR AG LEADER DEALER FOR
APPLICABLE WARRANTY INFORMATION.

Notices

USA

NOTE – FCC Part 15 rules; paragraph 15.105

This equipment has been tested and found to comply
with the limits for a Class A digital device, pursuant to
Part 15 of the FCC Rules. These limits are designed to
provide reasonable protection against harmful
interference when the equipment is operated in a
commercial environment. This 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
communications. Operation of this equipment in a
residential area is likely to cause harmful interference, in
which case, you, the user, will be required to correct the
interference at your own expense.

If this equipment does cause harmful interference to
radio or television reception, which can be determined
by turning the equipment off and on, the user is
encouraged to try to correct the interference by one or
more of the following measures:

– Reorient or relocate the receiving antenna.
– Increase the separation between the equipment and

the receiver.

– Connect the equipment into an outlet on a circuit

different from that to which the receiver is connected.

– Consult the dealer or an experienced radio/TV

technician for help.

Changes and modifications not expressly approved by
the manufacturer or registrant of this equipment can void
your authority to operate this equipment under Federal
Communications Commission rules.

Europe

This product has been tested and found to comply with
the requirements for the European Directive
75/322/EEC as amended by 2000/2/EC thereby
satisfying the requirements for e-mark compliance for
use in agricultural vehicles in the European Economic
Area (EEA).

This product has been tested and found to comply with
the requirements for a Class A device pursuant to
European Council Directive 89/336/EEC on EMC,
thereby satisfying the requirements for CE Marking and
sale within the European Economic Area (EEA).

Warning – This is a Class A product. In a domestic

environment this product may cause radio

C

interference in which case you may be required to
take adequate measures.

GPS 5100 Receiver User Guide iii

Declaration of Conformity

This product conforms to the following standards, and therefore complies with the requirements of the R&TTE
Directive 1999/5/EC, which specifies compliance with the essential requirements of EMC Directive 89/336/EEC and
Low Voltage Directive 73/23/EEC.

EMC Emissions BSEN 55022:1998 (W/A1:00) Class A

EMC Immunity EN 55024:1998

Safety EN 60950:2000

Mark First Applied 03

The technical file is maintained at Trimble Navigation Limited, 749 North Mary Avenue, PO Box 3642, Sunnyvale, CA
94088-3642, USA.

iv GPS 5100 Receiver User Guide

Contents

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Related Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Technical Assistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Standard Features of the GPS 5100 Receiver. . . . . . . . . . . . . . . . . 4

Receiver Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Receiver Input/Output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

LED Indicator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

GPS Positioning Methods. . . . . . . . . . . . . . . . . . . . . . . . . . 10

RTK GPS positioning . . . . . . . . . . . . . . . . . . . . . . . . 10

Differential GPS positioning (DGPS) . . . . . . . . . . . . . . . . 11

Autonomous GPS positioning . . . . . . . . . . . . . . . . . . . . 12

Sources of Error in GPS Positioning . . . . . . . . . . . . . . . . . . . . 13

Coordinate systems. . . . . . . . . . . . . . . . . . . . . . . . . . 15

3 Installing the Receiver. . . . . . . . . . . . . . . . . . . . 17

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

System Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Optional extra . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Mounting the Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Choosing a location . . . . . . . . . . . . . . . . . . . . . . . . . 19

Environmental conditions . . . . . . . . . . . . . . . . . . . . . . 20

Electrical interference . . . . . . . . . . . . . . . . . . . . . . . . 20

GPS 5100 Receiver User Guide v

Contents

Connecting to an External Device . . . . . . . . . . . . . . . . . . . . . 21

Connectors and Pinouts . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Port A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Port B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

4 Configuring the Receiver . . . . . . . . . . . . . . . . . . 27

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

AgRemote Home Screen . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Configuring Differential GPS. . . . . . . . . . . . . . . . . . . . . . . . 30

OmniSTAR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

WAAS/EGNOS . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Configuring the GPS 5100 Receiver to Operate in RTK Mode. . . . . . . 33

Configuring the Communication Ports . . . . . . . . . . . . . . . . . . . 33

Configuring input/output communication . . . . . . . . . . . . . . 34

5 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . 39

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Problems and Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Troubleshooting Flowcharts . . . . . . . . . . . . . . . . . . . . . . . . 48

A Specifications . . . . . . . . . . . . . . . . . . . . . . . . 55

GPS 5100 Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

GPS Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

L-Band Satellite Differential Correction Receiver . . . . . . . . . . . . . 58

Receiver Default Settings . . . . . . . . . . . . . . . . . . . . . . . . . . 58

B Additional Equipment Interface Requirements . . . . . . 59

Ag Leader Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

Third-Party Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

Third-Party Hardware. . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

vi GPS 5100 Receiver User Guide

CHAPTER

1

Introduction 1

Welcome to the GPS 5100 Receiver User Guide. This manual:

®

• Describes how to install and configure the Ag Leader
GPS receiver.

• Provides guidelines for connecting the receiver to an external
device.

• Provides guidelines for using the AgRemote utility to view and
configure the receiver correction sources and other operating
parameters.

5100

Even if you have used other Global Positioning System (GPS)
products before, Ag Leader recommends that you spend some time
reading this manual to learn about the special features of this product.

If you are not familiar with GPS, go to the Trimble
www.trimble.com for an interactive look at GPS.

GPS 5100 Receiver User Guide 1

®

website at

1 Introduction

1.1 Warnings

Always follow the instructions that accompany a warning.

C

1.2 Related Information

Warning – Indicates a potential hazard or unsafe practice that could result
in injury or property damage.

Release notes describe new features, provide information that is not
included in the manuals, and identify changes to the manuals.

1.3 Technical Assistance

If you have a problem and cannot find the information you need in the
product documentation, contact your local Ag Leader Reseller.

2 GPS 5100 Receiver User Guide

CHAPTER

2

Overview 2

In this chapter:

 Introduction

 Standard Features of the GPS 5100 Receiver

 Receiver Connections

 Receiver Input/Output

 LED Indicator

 GPS Positioning Methods

 Sources of Error in GPS Positioning

GPS 5100 Receiver User Guide 3

2 Overview

2.1 Introduction

This chapter describes the GPS 5100 receiver and gives an overview of
GPS, DGPS, and related information. When used with a Real-Time
Kinematic (RTK) base station, the GPS 5100 receiver provides RTK
positioning for high-accuracy, centimeter-level applications. For
physical specifications, see Appendix A, Specifications.

2.2 Standard Features of the GPS 5100 Receiver

A standard GPS 5100 receiver provides the following features:

• 12 GPS (C/A-code) tracking channels, code carrier channels

• Horizontal RTK positioning accuracy 2.5 cm (0.98 in) + 2 ppm,
2 sigma; vertical RTK positioning accuracy 3.7 cm (1.46 in)
+ 2ppm, 2sigma

• Submeter differential accuracy (RMS), assuming at least five
satellites and a PDOP of less than four

• Combined GPS/DGPS receiver and antenna

• System level cable

• AgRemote utility with four-button keypad to configure and view
system properties (download from the Ag Leader website at
www.agleader.com)

• LED status indicator

• The receiver outputs a 1 PPS (pulse per second) strobe signal on
both ports. This signal enables an external instrument to
synchronize its internal time with a time derived from the very
accurate GPS system time.

• WAAS differential correction compatibility

• Field computer compatibility

• EVEREST™ multipath rejection technology

• OmniSTAR VBS and HP positioning compatibility

4 GPS 5100 Receiver User Guide

Overview 2

• Two ports that support both CAN 2.0B and RS-232:

CAN

– J1939 and NMEA 2000 messages

Note – The GPS 5100 receiver is ISO 11783 compliant. It
supports some ISO 11783 messages.

RS-232

– NMEA-0183 output: GGA, GLL, GRS, GST, GSA, GSV,

MSS, RMC, VTG, ZDA, XTE (the default NMEA
messages are GGA, GSA, VTG, and RMC)

Note – PTNLDG, PTNLEV, PTNLGGK, PTNLID, and
PTNLSM are Trimble proprietary NMEA output messages.

– RTCM SC-104 output

– Trimble Standard Interface Protocol (TSIP) input and

output

2.3 Receiver Connections

Figure 2.1 shows the connector ports and the LED indicator on the
GPS 5100 receiver.

Figure 2.1 GPS 5100 receiver connector ports

Port A Port B

LED indicator

GPS 5100 Receiver User Guide 5

2 Overview

The two connectors (Port A and Port B) can perform the following
functions:

• accept power

• accept TSIP, RTCM, ASCII, and (if enabled) CMR inputs

• output RTCM, TSIP, and NMEA messages

• output 1 PPS signals

• provide support for the J1939 (CAN) serial bus

For more information about the inputs, outputs, and LED indicators,
see the information in the rest of this section.

2.4 Receiver Input/Output

The GPS 5100 receiver data/power cable connects to a receiver
connector port to supply power. It also enables the following data
exchanges:

• TSIP, RTCM, and ASCII input from an external device

The receiver is able to receive ASCII data from an external
device, convert this data into an NMEA message, and export the
message to another device. TSIP command packets configure
and monitor GPS and DGPS parameters. The receiver is also
able to accept RTCM data from an external device, such as a
radio.

• CMR input from an external device

If the receiver is to be used in RTK mode, set the port that is
connected to the radio to the RtkLnk protocol. This protocol
enables the receiver to receive CMR messages.

• TSIP and NMEA output to an external device

When you are using an external radio, the receiver can also
receive DGPS corrections.

TSIP is input/output when communicating with AgRemote.

6 GPS 5100 Receiver User Guide

Overview 2

NMEA is output when the receiver is exporting GPS position
information to an external device, such as a yield monitor, or to
a mapping software program.

For more information on the National Marine Electronics
Association (NMEA) and Radio Technical Commission for
Maritime Services (RTCM) communication standard for GPS
receivers, go to the following websites:

– www.nmea.org

– www.rtcm.org

On the Trimble website (www.trimble.com), refer to the
document called NMEA-0183 Messages Guide for AgGPS
Receivers.

• 1 PPS output

To synchronize timing between external instruments and the
internal clock in the receiver, the connection port outputs a
strobe signal at 1 PPS (pulse per second). To output this signal,
the receiver must be tracking satellites and computing GPS
positions.

• J1939 (CAN) bus

Both connection ports on the receiver support the J1939
Controller Area Network (CAN) bus protocol. This protocol
standardizes the way multiple microprocessor-based electronic
control units (ECUs) communicate with each other over the
same pair of wires. It is used in off-highway machines, such as
those used in agriculture, construction, and forestry.

For more information, go to the Society of Automotive
Engineers (SAE) International website at
www.sae.org/servlets/index.

• ISO 11783 messages

Both CAN ports support some ISO 11783 messages.

GPS 5100 Receiver User Guide 7

2 Overview

Position output format

The GPS 5100 receiver outputs positions in Degrees, Minutes, and
Decimal Minutes (DDD°MM.m'). This is the NMEA standard format
and is commonly used worldwide for data transfer between electronic
equipment.

2.5 LED Indicator

The GPS 5100 receiver has an LED light that shows the status of the
receiver. The following tables describe the light sequences for each
positioning method.

Table 2.1 LED sequences with Satellite Differential GPS or Autonomous positioning

LED color LED flash Status

Off Off No power

Green Solid Normal operation: computing DGPS positions

Green Slow No DGPS corrections: computing DGPS positions using old

corrections

Green Fast No DGPS corrections approaching DGPS age limit: computing

DGPS positions using old corrections

Yellow Solid DGPS corrections being received but DGPS positions not yet being

computed: computing autonomous GPS positions

Yellow Slow No DGPS corrections: computing autonomous GPS positions

Yellow Fast Not enough GPS signals: not tracking enough satellites to compute

position

Note – WAAS/EGNOS and OmniSTAR VBS use the Satellite
Differential GPS positioning method.

8 GPS 5100 Receiver User Guide

Overview 2

Table 2.2 LED sequences with RTK positioning

LED color LED flash Status

Off Off No power

Green Solid Normal operation: computing fixed RTK positions

Green Slow Receiving CMR corrections but not initialized: computing float RTK

positions

Green Fast No CMR corrections: computing RTK position using old corrections

Yellow Solid Receiving CMR corrections but unable to calculate RTK position:

computing DGPS (if WAAS/EGNOS is unavailable) or autonomous
position

Yellow Slow No CMR corrections: computing DGPS or autonomous position

Yellow Fast Not receiving CMR corrections: not computing positions

Table 2.3 LED sequences with OmniSTAR HP positioning

LED color LED flash Status

Off Off No power

Green Solid Normal operation: computing converged OmniSTAR HP positions

Green Slow Receiving OmniSTAR HP corrections, but only able to compute

unconverged position

Green Fast Receiving OmniSTAR HP corrections, but an HP error occurred

Yellow Solid Receiving OmniSTAR HP corrections but unable to calculate a

position: computing DGPS or autonomous solution

Yellow Slow No OmniSTAR HP corrections: computing DGPS or autonomous

position

Yellow Fast Not tracking OmniSTAR HP corrections: no positions

GPS 5100 Receiver User Guide 9

2 Overview

2.6 GPS Positioning Methods

GPS positioning systems are used in different ways to provide
different levels of accuracy. Accuracy is measured in absolute terms
(you know exactly where you are in a fixed reference frame).

Table 2.4 summarizes the GPS positioning methods. Imperial units in
this table are rounded to two decimal places. The values shown are
2sigma.

Table 2.4 Absolute accuracy of GPS positioning methods

GPS positioning
method

Real-Time Kinematic
(RTK) GPS

Satellite Differential GPS OmniSTAR VBS 78 cm (30.71 in)

Satellite Differential GPS WAAS/EGNOS 95 cm (37.40 in)

OmniSTAR HP
Differential GPS

1

Convergence time can vary, depending on the environment. Time to the first fix (submeter accuracy) is typically

<30 seconds; time to the first high accuracy fix (<10 cm accuracy) is typically <30 minutes.

Corrections used Approximate absolute accuracy

Trimble CMR
corrections broadcast
by a local base station

OmniSTAR HP 10 cm (3.94 in) after the signal has fully

2.5 cm (0.98 in) + 2 ppm horizontal
accuracy,

3.7 cm (1.46 in) + 2 ppm vertical accuracy

converged

1

For more information about each positioning method, see below.

26.1 RTK GPS positioning

The GPS 5100 receiver uses the RTK positioning method to achieve
centimeter-level accuracy. To use the RTK method, you must first set
up a base station. The base station uses a radio link to broadcast RTK
corrections to one or more rover receivers. The GPS 5100 receiver is a
rover receiver, so another compatible receiver, such as a Trimble
MS750™ or Trimble AgGPS® 214 GPS receiver, must be used as the
base station.

10 GPS 5100 Receiver User Guide

The rover receiver uses RTK corrections from the base station to
calculate its position to centimeter-level accuracy. As part of this
process, the rover receiver must calculate an initialization. This takes a
few seconds. While the receiver is initializing, an RTK Float solution
is generated. Once initialized, an RTK Fixed solution is generated. It is
the RTK Fixed solution that provides centimeter-level accuracy.

The parts per million (ppm) error is dependent on the distance
(baseline length) between the base and rover receiver. For example, if
the distance is 10 km, a 2 ppm error equals 20 mm.

For more information about RTK positioning, go to the Trimble
website at www.trimble.com/

26.2 Differential GPS positioning (DGPS)

For differential positioning, the GPS 5100 receiver uses corrections
from WAAS/EGNOS satellites or from OmniSTAR VBS or HP
satellites.

These differential systems use special algorithms to provide
differential corrections that allow the rover receiver to calculate its
position more accurately.

Overview 2

Free corrections

WAAS/EGNOS corrections are free in North America and Europe.
For more information about WAAS, go to the Federal Aviation
Administration website at
http://gps.faa.gov/Programs/WAAS/waas.htm.

For more information about EGNOS, go to the European Space
Agency website at
www.esa.int/export/esaSA/GGG63950NDC_navigation_0.html.

GPS 5100 Receiver User Guide 11

2 Overview

Subscription-based corrections

The GPS 5100 receiver uses OmniSTAR HP or OmniSTAR VBS
differential corrections in the same way that it uses WAAS/EGNOS
corrections.

OmniSTAR corrections are provided on a subscription basis.

The corrections that are produced by OmniSTAR HP algorithms are
more accurate than the corrections that are produced by OmniSTAR
VBS algorithms. The accuracy of the positions reported using
OmniSTAR HP increases with the time that has elapsed since the
instrument was turned on. This process is called convergence.
Convergence to where the error is estimated to be below 30 cm
(approximate 12 inches) typically takes around 20 minutes. Factors
that influence the time to convergence include the environment, the
geographical location, and the distance to the closest OmniSTAR
corrections base station. OmniSTAR is continually improving the
service.

For more information about OmniSTAR, go to the OmniSTAR
website at www.omnistar.com. For information about activating an
OmniSTAR subscription, see OmniSTAR, page 31.

26.3 Autonomous GPS positioning

Autonomous GPS positioning uses no corrections. The rover receiver
calculates its position using only the GPS signals it receives. This
method does not have high absolute accuracy, but the relative accuracy
is comparable to the other methods.

12 GPS 5100 Receiver User Guide

2.7 Sources of Error in GPS Positioning

The GPS positioning method influences the accuracy of the GPS
position that is output by the GPS 5100 receiver. The factors described
in Table 2.5 also affect GPS accuracy.

Table 2.5 Factors that influence the accuracy of GPS positions

Overview 2

Condition Optimum

value

Atmospheric
effects

Number of
satellites used

> 5 To calculate a 3D position (latitude and longitude, altitude, and

Description

GPS signals are degraded as they travel through the
ionosphere. The error introduced is in the range of 10 meters.

The error is removed by using a differential or RTK positioning
method.

time), four or more satellites must be visible. To calculate a 2D
position (latitude and longitude, and time), three or more
satellites must be visible. For RTK positioning, five satellites are
needed for initialization. Once initialized, four or more satellites
provide RTK positions. The number of visible satellites
constantly changes and is typically in the range 5 through 9.
The GPS 5100 receiver can track up to 12 satellites
simultaneously.

Note – To see when the maximum number of GPS satellites are
available, use the planning software and a current ephemeris
(satellite history) file. Both files are available free from the
Trimble website at www.trimble.com.

Maximum PDOP < 4 Position Dilution of Precision (PDOP) is a unitless, computed

measurement of the geometry of satellites above the current
location of the receiver. A low PDOP means that the positioning
of satellites in the sky is good, and therefore good positional
accuracy is obtained.

GPS 5100 Receiver User Guide 13

2 Overview

Table 2.5 Factors that influence the accuracy of GPS positions (continued)

Condition Optimum

value

Signal-to-noise
ratio

Minimum
elevation

Multipath
environment

RTCM­compatible
corrections

RTK Base station
coordinate
accuracy

Multiple RTK
base stations

> 6 Signal-to-noise ratio (SNR) is a measure of the signal strength

> 10 Satellites that are low on the horizon typically produce weak

Low Multipath errors are caused when GPS signals are reflected off

Description

against electrical background noise. A high SNR gives better
accuracy.

Normal values are:

•GPS 6

• WAAS 3+

• OmniSTAR HP/VBS 6+

and noisy signals and are more difficult for the receiver to track.
Satellites below the minimum elevation angle are not tracked.

nearby objects and reach the receiver by two or more different
paths. The receiver incorporates the EVEREST multipath
rejection option.

These corrections are broadcast from a Trimble AgGPS 214,
MS750, or equivalent reference station.

For RTK positioning, it is important to know the base station
coordinates accurately. Any error in the position of the base
station affects the position of the rover; every 10 m of error in a
base station coordinate can introduce up to 1 ppm scale error
on every measured baseline. For example, an error of 10 m in
the base station position produces an error of 10 mm over a
10 km baseline to the rover.

For more information about how to make sure the position of
your base station is accurate, refer to the manual for your base
station receiver.

If you are using several base stations to provide RTK
corrections to a large site area, all base stations must be
coordinated relative to one another. If they are not, the absolute
positions at the rover will be in error.

14 GPS 5100 Receiver User Guide

27.1 Coordinate systems

Geographic data obtained from different sources must be referenced to
the same datum, ellipsoid, and coordinate format. Different formats
provide different coordinate values for any geographic location. In
North America, the datums NAD-27 and NAD-83 are commonly used
in Agricultural mapping applications.

The GPS 5100 receiver outputs position coordinates in several datums
and ellipsoids depending on the GPS positioning method being used.
See Table 2.6.

Table 2.6 DGPS coordinate systems

GPS positioning method Datum Ellipsoid

None – Autonomous mode WGS-84

OmniSTAR VBS North American Beams NAD-83

OmniSTAR VBS Rest of World Beams ITRF

OmniSTAR HP ITRF 2000 ITRF 2000

WAAS Beams WGS-84 WGS-84

RTK WGS-84 WGS-84

1

World Geodetic System (WGS) 1984. Datum and ellipsoid.

2

North American Datum (NAD) 1983. Equivalent to WGS-84 in North America.

3

International Terrestrial Reference Frame (ITRF). Contact the DGPS provider for details.

Overview 2

1

2

3

WGS-84

GRS-80

GRS-80

For more information, go to the National Geodetic Survey website at
www.ngs.noaa.gov/faq.shtml#WhatDatum

GPS 5100 Receiver User Guide 15

2 Overview

16 GPS 5100 Receiver User Guide

CHAPTER

3

Installing the Receiver 3

In this chapter:

 Introduction

 System Components

 Mounting the Receiver

 Connecting to an External Device

 Connectors and Pinouts

GPS 5100 Receiver User Guide 17