User Guide
Trimble® AG-372 GNSS Receiver
Version 1.00
Revision A
June 2012
Part Number 56110-01-ENG
*56110-01-ENG*
F
Contact Information
Trimble Navigation Limited
Agriculture Business Area
9290 Bond Street, Suite 102
Overland Park, KS 66214
USA
+1-913-495-2700 Phone
trimble_support@trimble.com
www.trimble.com
Legal Notices
© 2012, Trimble Navigation Limited. All rights reserved.
Trimble, the Globe & Triangle logo, and AgGPS are trademarks of
Trimble Navigation Limited, registered in the United States and other
countries. Autopilot, CenterPoint, EVEREST, and RTX 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 June 2012 release (Revision A) of the Trimble AG-372 GNSS
Receiver User Guide, part number 56110-01-ENG. It applies to version
1.00 of the AG-372 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
Trimble Navigation Limited 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 one (1) year starting from the date of
delivery. The warranty set forth in this paragraph shall not apply to
software products.
Software License, Limited Warranty
This Trimble 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. Trimble
warrants that this Trimble Software product will substantially conform
to Trimble’s applicable published specifications for the Software for a
period of ninety (90) days, starting from the date of delivery.
Warranty Remedies
Trimble's sole liability and your exclusive remedy under the warranties
set forth above shall be, at Trimble’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 Trimble in accordance with Trimble’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 Trimble'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 Trimble 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 Trimble; (ii) the
operation of the Product or Software under any specification other
than, or in addition to, Trimble's standard specifications for its
products; (iii) the unauthorized, installation, modification, or use of the
Product or Software; (iv) 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). Trimble
does not warrant or guarantee the results obtained through the use of
the Product.
THE WARRANTIES ABOVE STATE TRIMBLE'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 TRIMBLE NAVIGATION LIMITED 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 TRIMBLE 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. TRIMBLE NAVIGATION LIMITED IS NOT
RESPONSI BLE FOR THE OPERATION OR FAILURE OF OPERATION OF GNSS
SATELLITES OR THE AVAILABILITY OF GNSS SATELLITE SIGNALS.
Limitation of Liability
TRIMBLE’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 P ERMITTED BY APPLICABLE LAW, IN NO
EVENT SHALL TRIMBLE 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
TRIMBLE 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 TRIMBLE. 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 TRIMBLE DEALER FOR APPLICABLE WARRANTY
INFORMATION.
2 Trimble AG-372 GNSS Receiver User Guide
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Related information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Technical assistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Standard features of the Trimble AG-372 GNSS receiver . . . . . . . . . . . . . . . . . . . . . 8
Receiver connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Receiver input/output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Position output format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
LED indicator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
GNSS positioning methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
RTK GNSS positioning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
CenterPoint RTX positioning (RTX). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Differential GNSS positioning (DGNSS) . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Autonomous GNSS positioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Sources of error in GNSS positioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Coordinate systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3 Installing the AG-372 GNSS Receiver . . . . . . . . . . . . . . . . . . . . . . . . . .17
System components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Optional extras . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Mounting the receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Choosing a location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Environmental conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Electrical interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Connecting to an external device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Connectors and pinouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Port A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Port B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Radar output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4 Installing the AG-715 Integrated Radio . . . . . . . . . . . . . . . . . . . . . . . . .25
Required tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Installation procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
5 Configuring the Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
Navigation map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
AgRemote Home screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Configuring Differential GNSS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
OmniSTAR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
WAAS/EGNOS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Configuring the Trimble AG-372 GNSS receiver to operate in CenterPoint RTX mode . . . . 35
Configuring the receiver for RTX (std-sat). . . . . . . . . . . . . . . . . . . . . . . . . 35
Trimble AG-372 GNSS Receiver User Guide 3
Contents
Configuring the receiver for RTX (std-cell) . . . . . . . . . . . . . . . . . . . . . . . . 36
Configuring the Trimble AG-372 GNSS receiver to operate in VRS mode . . . . . . . . . . . 38
Configuring the Trimble AG-372 GNSS receiver to operate in RTK mode . . . . . . . . . . . 40
Configuring the communication ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Configuring input/output communication . . . . . . . . . . . . . . . . . . . . . . . . 41
Changing the frequency settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Required equipment / software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Configuring the radio frequency, protocol, and radio link in the AgRemote utility . . 43
6 Troubleshooting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47
Global Navigation Satellite System (GNSS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Interference. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
GNSS receiver. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
AgRemote utility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
FlashLoader 200 upgrade utility. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
A Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55
Physical characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
GNSS channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
L-band satellite differential correction receiver . . . . . . . . . . . . . . . . . . . . . . . . . 58
Receiver default settings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
B Third-Party Interface Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . .59
Third-party software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Third-party hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
4 Trimble AG-372 GNSS Receiver User Guide
CHAPTER
1
Introduction 1
In this chapter:
Warnings
Related information
Technical assistance
The Trimble AG-372 GNSS Receiver User Guide:
• Describes how to install and configure the
Trimble
• 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.
Even if you have used another Global Navigation
Satellite System (GNSS) product before, Trimble
recommends that you spend some time reading
this manual to learn about the special features
of this product.
If you are not familiar with GNSS, go to the
Trimble website at
interactive look at Trimble and GNSS.
®
AG-372 GNSS receiver.
www.trimble.com for an
Trimble AG-372 GNSS Receiver User Guide 5
1 Introduction
Warnings
Always follow the instructions that accompany a warning.
C
C
WARNING – Indicates a potential hazard or unsafe practice that could result in injury or
property damage.
WARNING – For continued protection against the risk of fire, the power source (lead) to
the model AG-372 receiver should be provided with a 10 A (maximum) fuse.
Related information
Release notes describe new features, provide information that is not included in the
manuals, and identify changes to the manuals. You can download release notes from the
Trimble website.
Technical assistance
If you have a problem and cannot find the information you need in the product
documentation, contact your local Trimble Reseller
6 Trimble AG-372 GNSS Receiver User Guide
CHAPTER
2
Overview 2
In this chapter:
Standard features of the Trimble AG-372
GNSS receiver
Receiver connections
Receiver input/output
LED indicator
GNSS positioning methods
Sources of error in GNSS positioning
This chapter describes the Trimble AG-372 GNSS
receiver and gives an overview of GNSS, DGNSS,
and related information.
When used with a Real-Time Kinematic (RTK)
base station, the Trimble AG-372 GNSS receiver
provides RTK positioning for high-accuracy,
centimeter-level applications. For physical
specifications, see
Appendix A, Specifications.
Trimble AG-372 GNSS Receiver User Guide 7
2 Overview
Standard features of the Trimble AG-372 GNSS receiver
A standard Trimble AG-372 GNSS receiver provides the following features:
• 220 GNSS tracking channels, which can track up to 44 satellites
• GLONASS tracking ability
• Submeter differential accuracy (RMS), assuming at least five satellites and a PDOP of
less than four
• Combined GNSS/DGNSS receiver and antenna
• AgRemote utility with four-button keypad to configure and view system properties.
You can download this utility from the Trimble website at
• 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 GNSS system time.
• Radar output
• WAAS and EGNOS differential correction compatibility
• EVEREST
™
multipath rejection technology
www.trimble.com.
• OmniSTAR HP, G2, XP, and VBS positioning compatibility
• Trimble CenterPoint
• Two ports that support both CAN 2.0B and RS-232:
™
RTX™ capability
CAN
– J1939 and NMEA 2000 messages
Note – The Trimble AG-372 GNSS 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
8 Trimble AG-372 GNSS Receiver User Guide
Receiver connections
LED indicator
Port A Port B
The following figure shows the connector ports and the LED indicator on the AG-372 GNSS
receiver:
The two connectors (Port A and Port B) can do the following:
• Accept power
• Accept TSIP, RTCM, ASCII, and (if enabled) CMR inputs
Overview 2
• 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.
Receiver input/output
The Trimble AG-372 GNSS receiver data/power cable (P/N 50166) 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 GNSS and DGNSS 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, see
RTK mode, page 40. This protocol enables the receiver to receive CMR messages.
Configuring the Trimble AG-372 GNSS receiver to operate in
• TSIP and NMEA output to an external device
– When you are using an external or integrated radio, the receiver can also receive
DGNSS corrections.
Trimble AG-372 GNSS Receiver User Guide 9
2 Overview
– TSIP is input/output when communicating with AgRemote.
– NMEA is output when the receiver is exporting GNSS 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 GNSS 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 GNSS
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
• ISO 11783 messages
www.sae.org/servlets/index.
Both CAN ports support some ISO 11783 messages.
Position output format
The Trimble AG-372 GNSS 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.
10 Trimble AG-372 GNSS Receiver User Guide
Overview 2
LED indicator
The Trimble AG-372 GNSS receiver has an LED light that shows the status of the receiver.
The following tables describe the light sequences for each positioning method.
Note – Fast LED flash is approximately 3 flashes per second. Slow LED flash is approximately
1 flash per second.
Table 2.1 LED sequences with Satellite Differential GNSS or autonomous positioning
LED color LED flash Status
Off Off No power
Green Solid Normal operation: computing DGNSS positions
Green Slow No DGNSS corrections: computing DGNSS positions using old corrections
Green Fast No DGNSS corrections approaching DGNSS age limit: computing DGNSS positions
Yell ow Solid DGNSS corrections being received but DGNSS positions not yet being computed:
Yell ow Slow No DGNSS corrections: computing autonomous GNSS positions
using old corrections
computing autonomous GNSS positions
Yell ow Fast Not enough GNSS signals: not tracking enough satellites to compute position
Note – WAAS/EGNOS and OmniSTAR VBS use the Satellite Differential GNSS positioning
method.
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
Yell ow Solid Receiving CMR corrections but unable to calculate RTK position: computing DGNSS
(if WAAS/EGNOS is unavailable) or autonomous position
Yell ow Slow No CMR corrections: computing DGNSS or autonomous position
Yell ow Fast Not receiving CMR corrections: not computing positions
Table 2.3 LED sequences with OmniSTAR HP positioning
LED color LED flash Status
Off
Green
Green
Off No power
Solid Normal operation: computing converged OmniSTAR HP positions
Slow Receiving OmniSTAR HP corrections, but only able to compute unconverged
position
Trimble AG-372 GNSS Receiver User Guide 11
2 Overview
Table 2.3 LED sequences with OmniSTAR HP positioning (continued)
LED color LED flash Status
Green
Yellow
Yellow
Yellow
Fast Receiving OmniSTAR HP corrections, but an HP error occurred
Solid Receiving OmniSTAR HP corrections but unable to calculate a position: computing
DGNSS or autonomous solution
Slow No OmniSTAR HP corrections: computing DGNSS or autonomous position
Fast Not tracking OmniSTAR HP corrections: no positions
GNSS positioning methods
GNSS positioning systems are used in different ways to provide different levels of accuracy.
Accuracy is measured in absolute terms, that is, you know exactly where you are in a fixed
reference frame.
Table 2.4 summarizes the GNSS positioning methods. The values shown are 2 sigma.
Table 2.4 Absolute accuracy of GNSS positioning methods
GNSS positioning method Corrections used Approximate absolute accuracy
Real-Time Kinematic (RTK) GNSS Trimble CMR corrections
broadcast by a local base
station
CenterPoint RTX technology CenterPoint RTX 4 cm (1.5 inch)
Satellite Differential GNSS OmniSTAR VBS 78 cm (30.7 inch)
Satellite Differential GNSS WAAS/EGNOS 95 cm (37.4 inch)
OmniSTAR HP Differential GNSS OmniSTAR HP 10 cm (3.9 inch) after the signal has fully
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.
2.5 cm (1 inch) + 2 ppm horizontal
accuracy,
3.7 cm (1.5 inch) + 2 ppm vertical
accuracy
converged
1
For more information about each positioning method, see below.
RTK GNSS positioning
The Trimble AG-372 GNSS receiver uses the RTK positioning method to achieve centimeterlevel 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 Trimble
AG-372 GNSS receiver is a rover receiver, so another compatible receiver, such as a Trimble
AgGPS 442, AgGPS 542, AgGPS RTK Base 450, or AgGPS RTK Base 900 receiver, must be
used as the base station.
12 Trimble AG-372 GNSS 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/GNSS/
CenterPoint RTX positioning (RTX)
Trimble CenterPoint RTX is a GPS and GLONASS-enabled correction service built on
patent-pending Trimble RTX technology. This breakthrough technology provides
high-accuracy GNSS positioning without the use of traditional reference station-based
differential RTK infrastructure.
CenterPoint RTX corrections are provided on as subscription basis.
Overview 2
For more information about the CenterPoint RTX correction service, see
http://www.trimble.com/agriculture/CorrectionServices/
For more information on activating a CenterPoint RTX subscription, see Configuring the
Trimble AG-372 GNSS receiver to operate in CenterPoint RTX mode, page 35.
Differential GNSS positioning (DGNSS)
For differential positioning, the Trimble AG-372 GNSS receiver uses corrections from
WAAS/EGNOS satellites or from OmniSTAR HP, XP, G2, or VBS satellites.
These differential systems use special algorithms to provide differential corrections that
allow the rover receiver to calculate its position more accurately. Not all corrections
services support the use of GLONASS satellites in their solution.
Free corrections
WAAS corrections are free in North America and EGNOS corrections are free in Europe. For
more information about WAAS, go to the Federal Aviation Administration website at
http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/na
vservices/gnss/waas/
For more information about EGNOS, go to the European Space Agency website at
http://www.esa.int/esaNA/egnos.html.
Trimble AG-372 GNSS Receiver User Guide 13
2 Overview
Subscription-based corrections
The Trimble AG-372 GNSS receiver can use OmniSTAR™ HP, XP, G2, or VBS differential
corrections.
OmniSTAR corrections are provided on a subscription basis.
For more information about OmniSTAR, go to the OmniSTAR website at
www.omnistar.com. For information about activating an OmniSTAR subscription, see
OmniSTAR, page 34.
Autonomous GNSS positioning
Autonomous GNSS positioning uses no corrections. The rover receiver calculates its
position using only the GNSS signals it receives. This method does not have high absolute
accuracy, but the relative accuracy is comparable to the other methods.
Sources of error in GNSS positioning
The GNSS positioning method influences the accuracy of the GNSS position that is output
by the Trimble AG-372 GNSS receiver. The factors described in Table 2.5 also affect GNSS
accuracy.
Table 2.5 Factors that influence the accuracy of GNSS positions
Condition Optimum
value
Atmospheric
effects
Number of
satellites used
Maximum PDOP < 4 Position Dilution of Precision (PDOP) is a unitless, computed measurement
> 5 To calculate a 3D position (latitude and longitude, altitude, and time), four
Description
GNSS 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.
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 receiver
can track up to 44 satellites simultaneously.
Note – To see when the maximum number of GNSS satellites are available,
use the Trimble Planning software and a current ephemeris (satellite
history) file. Both files are available free from the Trimble website at
www.trimble.com.
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.
14 Trimble AG-372 GNSS Receiver User Guide
Table 2.5 Factors that influence the accuracy of GNSS positions (continued)
Overview 2
Condition Optimum
Description
value
Signal-to-noise
ratio
Signal-to-noise ratio (SNR) is a measure of the signal strength against
electrical background noise. A high SNR gives better accuracy.
SNR can be degraded by other electronic equipment operating nearby,
including transmitters, cell phones, or data modems. It may also be
degraded by solar flares and changing atmospheric conditions.
Minimum elevation > 10° Satellites that are low on the horizon typically produce weak and noisy
signals and are more difficult for the receiver to track. Satellites below the
minimum elevation angle are not tracked.
Multipath
environment
Low Multipath errors are caused when GNSS signals are reflected off nearby
objects and reach the receiver by two or more different paths. The receiver
incorporates the EVEREST multipath rejection option.
RTCM-compatible
corrections
RTK Base station
coordinate
accuracy
These corrections are broadcast from an
Ag
GPS 442, AgGPS 542, 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.
Multiple RTK base
stations
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. For more
information about how to use several base stations to cover your site,
contact your local Trimble Reseller.
Trimble AG-372 GNSS Receiver User Guide 15
2 Overview
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 Trimble AG-372 GNSS receiver outputs position coordinates in several datums and
ellipsoids depending on the GNSS positioning method being used. See Table 2.6.
Table 2.6 DGNSS coordinate systems
GNSS positioning method Datum Ellipsoid
None – Autonomous mode WGS-84
OmniSTAR VBS North American Beams NAD-83
OmniSTAR VBS Rest of World Beams ITRF 2005
OmniSTAR HP, XP, and G2 ITRF 2005 ITRF 2005
WAAS Beams WGS-84 WGS-84
RTK WGS-84 WGS-84
1
2
3
WGS-84
GRS-80
ITRF 2005
RTX ITRF 2005 ITRF 2005
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 DGNSS provider for details.
For more information, go to the National Geodetic Survey website at
www.ngs.noaa.gov/faq.shtml#WhatDatum.
16 Trimble AG-372 GNSS Receiver User Guide
CHAPTER
3
Installing the AG-372 GNSS Receiver 3
In this chapter:
System components
Mounting the receiver
Connecting to an external device
Connectors and pinouts
Radar output
This chapter describes how to check the
equipment that you have received, set up the
AG-372 receiver, and connect the receiver to
another device.
Trimble AG-372 GNSS Receiver User Guide 17
3 Installing the AG-372 GNSS Receiver
System components
Check that you have received all components for the system that you purchased. If any
containers or components are damaged, immediately notify the shipping carrier. The
following components ar included:
Quantity Description
1 Trimble AG-372 GNSS receiver (P/N 56000-01)
1 System level cable (P/N 50165 or 50166)
1 Mounting plate assembly (P/N 51312-00)
1 Port B plug (P/N 51062)
1 Trimble AG-372 GNSS Receiver User Guide
(this manual, P/N 56100-00-ENG)
Optional extras
You may also have ordered one of the following receiver options:
• Passcode, AG-372 upgrade: DGPS to OmniSTAR XP/HP (P/N 87855)
• Passcode, AG-372 upgrade: OmniSTAR XP/HP to RTK (P/N 87858)
Mounting the receiver
C
WARNING – For continued protection against the risk of fire, the power source (lead) to
the model Trimble AG-372 GNSS receiver should be provided with a 10 A (maximum) fuse.
Secure the Trimble AG-372 GNSS receiver directly to the mounting plate assembly
(P/N 51312-00) and insert three bolts through the holes that are in the housing and in the
mounting plate assembly. Torque the bolts to 75–80 inch pounds.
Choosing a location
When choosing a location, consider the following:
Mount the receiver:
• On a flat surface along the centerline of the vehicle
• In any convenient location that is within 5.5 meters (18 ft) of the port on the external
instrument; if necessary, use the optional extension cable to connect the receiver and
external device
Note – If you are using a Trimble Autopilot™ system, please refer to the installation
instructions that are provided with the Autopilot system.
• At the highest point on the vehicle, with no metal surfaces blocking the receiver’s view
of the sky
18 Trimble AG-372 GNSS Receiver User Guide
Installing the AG-372 GNSS Receiver 3
• In such a way that it is not damaged when you drive the machine into a shed or
storage area
Do not mount the receiver:
• Close to stays, electrical cables, metal masts, CB radio antennas, cellular phone
antennas, air-conditioning units (machine cab blower fan), or machine accessory lights
• Near transmitting antennas, radar arrays, or satellite communication equipment
• Near areas that experience high vibration, excessive heat, electrical interference, and
strong magnetic fields
Note – A metal combine grain tank extension can block satellites.
Environmental conditions
Although the receiver has a waterproof housing, you should install it in a dry location. To
improve the performance and long-term reliability of the receiver, avoid exposure to
extreme environmental conditions, including:
• Water
• Excessive heat (> 70 °C or 158 °F)
• Excessive cold (< –30 °C or –22 °F)
• High vibration
• Corrosive fluids and gases
Electrical interference
As far as possible, when you install the receiver, you should avoid placing it near sources of
electrical and magnetic noise, such as:
• Gasoline engines (spark plugs)
• Computer monitor screens
• Alternators, generators, or magnetos
• Electric motors (blower fans)
• Equipment with DC-to-AC converters
• Switching power supplies
• Radio speakers
• High-voltage power lines
• CB radio antennas
• Cellular phone antennas
• Machine accessory lights
Trimble AG-372 GNSS Receiver User Guide 19
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