Garmin GPS 20X TECHNICAL SPECIFICATIONS

GPS 20x

TECHNICAL

SPECIFICATIONS

Garmin International, Inc.

st

1200 E. 151

Olathe, KS 66062 USA

190-00880-00, Revision A

January 2008

a

Street

© 2008 Garmin Ltd. or its subsidiaries

Garmin International, Inc.
1200 East 151

st

Street, Olathe, Kansas 66062, U.S.A.
Tel. [phone] or 800/800.1020
Fax [phone]

Garmin (Europe) Ltd.
Liberty House, Hounsdown Business Park,
Southampton, Hampshire, SO40 9RB, U. K.
Tel. [phone] (outside the UK) 0808 2380000 (within the UK)
Fax [phone]

Garmin Corporation
No. 68, Jangshu 2

nd

Road, Shijr, Taipei County, Taiwan
Tel. [phone]
Fax [phone]

All rights reserved. Except as expressly provided herein, no part of this manual may be reproduced, copied,
transmitted, disseminated, downloaded, or stored in any storage medium, for any purpose without the express prior
written consent of Garmin. Garmin hereby grants permission to download a single copy of this manual onto a hard
drive or other electronic storage medium to be viewed and to print one copy of this manual or of any revision hereto,
provided that such electronic or printed copy of this manual must contain the complete text of this copyright notice
and provided further that any unauthorized commercial distribution of this manual or any revision hereto is strictly
prohibited.

Information in this document is subject to change without notice. Garmin reserves the right to change or improve its
products and to make changes in the content without obligation to notify any person or organization of such changes
or improvements. Visit the Garmin Web site (

www.garmin.com) for current updates and supplemental information

concerning the use and operation of this and other Garmin products.
Garmin

®

, MapSource®, and WAAS Enabled® are registered trademarks of Garmin Ltd. or its subsidiaries and may

not be used without the express permission of Garmin.
Windows® is a registered trademark of the Microsoft Corporation.
Macintosh

®

is a registered trademark of Apple Inc.

Web site address: www.garmin.com

RECORD OF REVISIONS

Revision Revision

Description ECO #

Date

A 1/14/08 Initial Release --

190-00880-00 GPS 20x Technical Specifications Rev. A

Page i

TABLE OF CONTENTS

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

1.1 Cautions...........................................................................................................................................................1

1.2 Limited Warranty............................................................................................................................................2

1.3 Overview.........................................................................................................................................................3

1.4 Features...........................................................................................................................................................3

1.5 Technical Specifications..................................................................................................................................4

1.5.1 Physical Characteristics.....................................................................................................................................4

1.5.1.1 Size.................................................................................................................................................... 4

1.5.1.2 Weight............................................................................................................................................... 4

1.5.1.3 Color.................................................................................................................................................. 4

1.5.1.4 Case Material..................................................................................................................................... 4

1.5.1.5 Cable Length..................................................................................................................................... 4

1.5.2 Electrical Characteristics................................................................................................................................... 4

1.5.2.1 Input Voltage..................................................................................................................................... 4

1.5.2.2 Input Current..................................................................................................................................... 4

1.5.2.3 GPS Receiver Sensitivity .................................................................................................................. 4

1.5.2.4 Environmental Characteristics........................................................................................................... 4

1.5.3 GPS Performance.............................................................................................................................................. 4

1.5.3.1 Receiver............................................................................................................................................. 4

1.5.3.2 Acquisition Times............................................................................................................................. 4

1.5.3.3 Update Rate....................................................................................................................................... 4

1.5.3.4 Accuracy ........................................................................................................................................... 5

1.5.4 Interfaces........................................................................................................................................................... 5

1.5.4.1 GPS 20x Electrical Characteristics.................................................................................................... 5

1.5.4.2 Garmin Interface and Garmin USB Protocol..................................................................................... 5

2 Mechanical Characteristics & Mounting...............................................................................6

3 GPS 20x Software Interface....................................................................................................7

3.1 Transmitted NMEA 0183 Sentences...............................................................................................................7

3.1.1 Sentence Transmission Rate.............................................................................................................................. 7

3.1.2 Transmitted Time .............................................................................................................................................. 8

3.1.3 Global Positioning System Fix Data (GGA)..................................................................................................... 8

3.1.4 GPS DOP and Active Satellites (GSA)............................................................................................................. 9

3.1.5 GPS Satellites in View (GSV)...........................................................................................................................9

3.1.6 Recommended Minimum Specific GPS/TRANSIT Data (RMC)..................................................................... 9

3.1.7 Sensor Status Information (PGRMT).............................................................................................................. 10

Appendix A: Earth Datum List..................................................................................................11

Appendix B: Garmin Binary Output Format...........................................................................14

LIST OF TABLES AND FIGURES

Figure 1. GPS 20x Top Case Dimensions.....................................................................................................................6

Figure 2. GPS 20x Side View........................................................................................................................................6

Figure 3. GPS 20x End View ........................................................................................................................................6

Table 1: NMEA 0183 Output Sentence Order and Size................................................................................................7

190-00880-00 GPS 20x Technical Specifications Rev. A

Page ii

1 INTRODUCTION

1.1 CAUTIONS

CAUTION

The GPS system is operated by the government of the United States, which is solely responsible for its accuracy and
maintenance. Although the GPS 20x is a precision electronic NAVigation AID (NAVAID), any NAVAID can be
misused or misinterpreted, and therefore become unsafe. Use these products at your own risk. To reduce the risk,
carefully review and understand all aspects of these Technical Specifications before using the GPS 20x. When in
actual use, carefully compare indications from the GPS to all available navigation sources including the information
from other NAVAIDs, visual sightings, charts, etc. For safety, always resolve any discrepancies before continuing
navigation.

FCC

Compliance

This product has been tested and found to comply with Part 15 of the FCC interference limits for Class B digital
devices FOR HOME OR OFFICE USE. These limits are designed to pr ovi de m ore reas onable protection against
harmful interference in a residential installation, and are more stringent than “outdoor” requirements.

Operation of this device is subject to the following 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.

This equipment generates, uses, and can radiate radio frequency energy and may cause harmful interference to radio
communications if not installed and used in accordance with the instructions. However, there is no guarantee that
interference will not occur in a particular installation. 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 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 that is on a different circuit from the GPS unit.

• Consult the dealer or an experienced radio/TV technician for help.

This product does not contain any user-serviceable parts. Repairs should only be made by an authorized Garmin
service center. Unauthorized repairs or modifications could result in permanent damage to the equipment, and void
your warranty and your authority to operate this device under Part 15 regulatio ns.

190-00880-00 GPS 20x Technical Specifications Rev. A

Page 1

1.2 LIMITED WARRANTY

This Garmin product is warranted to be free from defects in materials or workmanship for one year from the date of
purchase. Within this period, Garmin will at its sole option, repair or replace any components that fail in normal use.
Such repairs or replacement will be made at no charge to the customer for parts or labor, provided that the customer
shall be responsible for any transportation cost. This warranty does not cover failures due to abuse, misuse, accident
or unauthorized alteration or repairs.

This product is intended to be used only as a travel aid and must not be used for any purpose requiring precise
measurement of direction, distance, location, or topography. Garmin makes no warranty as to the accuracy or
completeness of map data in this product.

THE WARRANTIES AND REMEDIES CONTAINED HEREIN ARE E XCLUSIVE AND IN LIEU OF ALL
OTHER WARRANTIES EXPRESS OR IMPLIED OR STATUTORY, INCLUDING ANY LIABILITY ARISING
UNDER ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PART I CULAR PURPOSE,
STATUTORY OR OTHERWISE. THIS WARRANTY GIVES YO U SPECIF IC LE GAL RIGHTS, WHICH MAY
VARY FROM STATE TO STATE.

IN NO EVENT SHALL GARMIN BE LIABLE FOR ANY INCIDENTAL, SPECIAL, INDIRECT OR
CONSEQUENTIAL DAMAGES, WHETHER RESULTING FROM THE USE, MISUSE, OR INABILITY TO
USE THIS PRODUCT OR FROM DEFECTS IN THE PRODUCT. Some states do not allow the exclusion of
incidental or consequential damages, so the above limitations may not apply to you.

Garmin retains the exclusive right to repair or replace the unit or software or offer a full refund of the purchase price
at its sole discretion. SUCH REMEDY SHALL BE YOUR SOLE AND EXCLUSIVE REMEDY FOR ANY
BREACH OF WARRANTY.

To obtain warranty service, contact your local Garmin authorized dealer, or call Garmin Product Support at one of
the numbers shown below for shipping instructions and an RMA tracking number. The unit should be securely
packed with the tracking number clearly written on the outside
charges prepaid, to any Garmin warranty service station. A copy of the original sales receipt is required as the proof
of purchase for warranty repairs.

of the package. The unit should then be sent, freight

Garmin International, Inc.
1200 East 151

st

Street,
Olathe, Kansas 66062, U.S.A.
Tel. [phone] or 800/800.1020
Fax [phone]

Garmin (Europe) Ltd.
Liberty House, Hounsdown Business Park,
Southampton, Hampshire, SO40 9RB, U. K.
Tel. [phone] (outside the UK) 0808 2380000 (within the UK)
Fax [phone]

Garmin Corporation
No. 68, Jangshu 2nd Road,
Shijr, Taipei County, Taiwan
Tel. [phone]
Fax [phone]

190-00880-00 GPS 20x Technical Specifications Rev. A

Page 2

1.3 OVERVIEW

The GPS 20x includes an embedded receiver and an antenna. The GPS 20x tracks multiple satellites at a time while
providing fast time-to-first-fix navigation updates once per second. This generation of GPS sensors includes the
capability of FAA Wide Area Augmentation System (WAAS) differential GPS.

The GPS 20x design uses the latest technology and high-level circuit integration to ach ieve superior performance
while minimizing space and power requirements. The hardware capability combined with software intelligence
makes the GPS 20x easy to integrate and use.

The GPS 20x requires minimal additional components to be supplied by an OEM or system integrator. A minimum
system must provide the GPS with a source of power and a clear view of the GPS satellites. Internal FLASH
memory allows the GPS to retain critical data such as satellite orbital parameters, last-known position, date and
time. End user interfaces such as keyboards and displays are the responsibility of the application designer.

The GPS 20x interfaces to a computer with an available USB port. Drivers are available for use on Windows
computers. Macintosh

®

and Linux drivers are not available from Garmin. After the drivers are loaded, the device

®

appears to the Windows operating system as a USB-connected device and appears in Device Manager as a Garmin
USB Device.

1.4 FEATURES

• GPS receiver tracks and uses multiple satellites for fast, accurate positioning and velocity estimates.

• Differential DGPS capability using real-time WAAS corrections yields position errors of less than 3

meters.

• Compact design is ideal for applications with minimal space.

• Binary format data output over the USB interface transmits packets once per second. Refer to

Garmin Binary Output Format

.

Appendix B:

• Downloadable Spanner application allows the GPS 20x to output NMEA 0183 sentences. Refer to section

3.1 Transmitted NMEA 0183 Sentences.

• FLASH-based program allows new software revisions through a Web site download.

• Non-volatile memory does not require battery backup.

• Onboard rechargeable backup battery can maintain the real-time clock for up to 10 days.

• Configurable parameters include expected position, current time and date, and preferred position fix type

(3D or automatic).

190-00880-00 GPS 20x Technical Specifications Rev. A

Page 3

1.5 TECHNICAL SPECIFICATIONS

Specifications are subject to change without notice.

1.5.1 Physical Characteristics

1.5.1.1 Size

1.7 in. (42.8 mm) long × 1.3 in. (32.4 mm) wide × 0.5 in. (12 mm) in height

1.5.1.2 Weight

1.1 oz (31.7 g)

1.5.1.3 Color

Silver

1.5.1.4 Case Material

Polycarbonate/Acrylonitrile-Butadiene-Styrene (PC/ABS)

1.5.1.5 Cable Length

1 meter

1.5.2 Electrical Characteristics

1.5.2.1 Input Voltage

4.4–5.5 Vdc

1.5.2.2 Input Current

110 mA @ 5.0 Vdc

1.5.2.3 GPS Receiver Sensitivity

-185 dBW minimum

1.5.2.4 Environmental Characteristics

• Operating Temperature: -30°C to +80°C (-22°F to +176°F)

• Storage Temperature: -40°C to +90°C (-40°F to +194°F)

1.5.3 GPS Performance

1.5.3.1 Receiver

WAAS Enabled® GPS receiver continuously tracks and uses multiple satellites to compute and update your position.

1.5.3.2 Acquisition Times

• Reacquisition: Less than 2 seconds

• Hot: Approx. 1 second (all data known)

• Warm: Approx. 38 seconds (initial position, time, and almanac known; ephemeris unknown)

• Cold: Approx. 45 seconds

1.5.3.3 Update Rate

1 record per second

190-00880-00 GPS 20x Technical Specifications Rev. A

Page 4

1.5.3.4 Accuracy

• GPS Standard Positioning Service (SPS)

Position: < 15 meters, 95% typical
Velocity: 0.1 knot RMS steady state

• WAAS

Position: < 3 meters, 95% typical
Velocity: 0.1 knot RMS steady state

• Dynamics: 999 knots velocity (only limited at altitude greater than 60,000 feet), 2g dynamics

1.5.4 Interfaces

1.5.4.1 GPS 20x Electrical Characteristics

USB 2.0 full-speed protocol compat i ble , as well as USB 1. 1 ful l -speed protocol.

1.5.4.2 Garmin Interface and Garmin USB Protocol

Refer to the Garmin Device Interface Specification found in the Garmin Device Interface SDK for information
about the Garmin Interface and the Garmin USB Protocol. At the time of this printing, this document is located on
the Garmin Web site at:

See

Appendix B: Garmin Binary Output Format for additional information concerning access to binary data from

the GPS 20x.
Using Spanner (an application that can provide NMEA output via a virtual COM port), the GPS 20x can send

NMEA 0183 output sentences. Spanner is available for free on the Garmin web site. To download the software, start

www.garmin.com/oem, select the GPS 20x, and then select Updates & Downloads.

at

www.garmin.com/support/commProtocol.html.

Available NMEA 0183 output sentences include GPGGA, GPGSA, GPGSV, GPRMC, and PGRM T (Garmin
proprietary sentence). See section

3.1 Transmitted NMEA 0183 Sentences for format descriptions.

190-00880-00 GPS 20x Technical Specifications Rev. A

Page 5

2 MECHANICAL CHARACTERISTICS

(

)

m

)

(

)

1.7 in.

1.3 in.(32.4 m

Figure 1. GPS 20x Top Case Dimensions

1.7 in.

(42.8 mm)

Figure 2. GPS 20x Side View

42.8 mm

0.5 in. (12 mm)

0.5 in.

Figure 3. GPS 20x End View

190-00880-00 GPS 20x Technical Specifications Rev. A

Page 6

12 mm

3 GPS 20x SOFTWARE INTERFACE

The GPS 20x transmits using the Garmin USB interface. The Garmin USB interface is discussed in the Garmin
Device Interface Specification found in the Garmin Device Interface SDK located on the Garmin Web site at:

www.garmin.com/support/commProtocol.html.

You can configure the GPS 20x to transmit binary data information over the USB interface. Refer to Appendix B:

Garmin Binary Output Format

.

3.1 TRANSMITTED NMEA 0183 SENTENCES

The following paragraphs define the sentences that can be transmitted by the GPS 20x using Spanner (an application
that can provide NMEA output via a virtual COM port). Spanner is available for free on the Garmin web site. To
download the software, start at

3.1.1 Sentence Transmission Rate

Sentences are transmitted with respect to the user selected baud rate.
The GPS sensor will transmit each sentence once per second. The sentences are not configurable.

www.garmin.com/oem, select the GPS 20x, and then select Updates & Downloads.

Sentence Maximum Characters

GPRMC 74
GPGGA 82

GPGSA 66
GPGSV 70

PGRMT 50

Table 1: NMEA 0183 Output Sentence Order and Size

The maximum number of fields allowed in a single sentence is 82 characters including delimiters. Values in the
table include the sentence start delimiter character “$” and the termination delimiter <CR><LF>.

190-00880-00 GPS 20x Technical Specifications Rev. A

Page 7

3.1.2 Transmitted Time

The GPS sensor outputs Coordinated Universal Time (UTC) date and time of day in the transmitted sentences.
Before the initial position fix, the on-board clock provides the date and time of day. After the initial position fix, the
date and time of day are calculated using GPS satellite information and are synchronized with the measurement
pulse output.

The GPS sensor uses information obtained from the GPS satellites to add or delete UTC leap seconds and correct the
transmitted date and time of day. The transmitted date and time of day for leap second correction follow the
guidelines in “National Institute of Standards and Technology Special Publication 432 (Revised 1990)” (f or sale by
the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C., 20402, U.S.A.).

When a positive leap second is required, one second is inserted at the beginning of the first hour (0h 0m 0s) of the
day that the positive leap is occurring. The minute containing the leap second is 61 seconds long. The GPS sensor
would have transmitted this information for the leap second added December 31, 1998 as follows:

$GPRMC,235959,A,3851.3651,N,09447.9382,W,000.0,221.9,071103,003.3,E*69
$GPRMC,000000,A,3851.3651,N,09447.9382,W,000.0,221.9,081103,003.3,E*67
$GPRMC,000000,A,3851.3651,N,09447.9382,W,000.0,221.9,081103,003.3,E*67
$GPRMC,000001,A,3851.3651,N,09447.9382,W,000.0,221.9,081103,003.3,E*66
If a negative leap second should be required, one second will be deleted at the end of some UTC month. The minute

containing the leap second will be only 59 seconds long. In this case, the GPS sensor will not transmit the time of
day 0h 0m 0s (the “zero” second) for the day from which the leap second is removed.

$GPRMC,235959,A,3851.3650,N,09447.9373,W,000.0,000.0,111103,003.3,E*69
$GPRMC,000001,A,3851.3650,N,09447.9373,W,000.0,000.0,121103,003.3,E*6A
$GPRMC,000002,A,3851.3650,N,09447.9373,W,000.0,000.0,121103,003.3,E*69

3.1.3 Global Positioning System Fix Data (GGA)

$GPGGA,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,M,<10>,M,<11>,<12>*hh<CR><LF>

<1> UTC time of position fix, hhmmss format
<2> Latitude, ddmm.mmmm format (leading zeros will be transmitted)
<3> Latitude hemisphere, N or S
<4> Longitude, dddmm.mmmm format (leading zeros will be transmitted)
<5> Longitude hemisphere, E or W
<6> GPS quality indication, 0 = fix not available, 1 = Non-differential GPS fix available, 2 =

Differential GPS (WAAS) fix available, 6 = Estimated
<7> Number of satellites in use, 00 to 12 (leading zeros will be transmitted)
<8> Horizontal dilution of precision, 0.5 to 99.9
<9> Antenna height above/below mean sea level, -9999.9 to 99999.9 meters

<10> Geoidal height, -999.9 to 9999.9 meters
<11> Null (Differential GPS)
<12> Null (Differential Reference Station ID)

190-00880-00 GPS 20x Technical Specifications Rev. A

Page 8

3.1.4 GPS DOP and Active Satellites (GSA)

$GPGSA,<1>,<2>,<3>,<3>,<3>,<3>,<3>,<3>,<3>,<3>,<3>,<3>,<3>,<3>,<4>,<5>,<6>*hh<CR><LF>

<1> Mode, M = Manual, A = Automatic
<2> Fix type, 1 = not available, 2 = 2D, 3 = 3D
<3> PRN number, 01 to 32, of satellite used in solution, up to 12 transmitted (leading zeros will be

transmitted)
<4> Position dilution of precision, 0.5 to 99.9
<5> Horizontal dilution of precision, 0.5 to 99.9
<6> Vertical dilution of precision, 0.5 to 99.9

3.1.5 GPS Satellites in View (GSV)

$GPGSV,<1>,<2>,<3>,<4>,<5>,<6>,<7>,...<4>,<5>,<6>,<7>*hh<CR><LF>

<1> Total number of GSV sentences to be transmitted
<2> Number of current GSV sentence
<3> Total number of satellites in view, 00 to 12 (leading zeros will be transmitted)
<4> Satellite PRN number, 01 to 32 (leading zeros will be transmitted)
<5> Satellite elevation, 00 to 90 degrees (leading zeros will be transmitted)
<6> Satellite azimuth, 000 to 359 degrees, true (leading zeros will be transmitted)
<7> Signal to noise ratio (C/No) 00 to 99 dB (leading zeros will be transmitted)

Note: Items <4>,<5>,<6>, and <7> repeat for each satellite in view to a maximum of four (4) satellites per sentence.
GSV will be repeated as necessary to output all satellites in view (up to 12 satellites). Unused satellite fields will be
truncated when less than four satellites are in the last GSV sentence.

3.1.6 Recommended Minimum Specific GPS/TRANSIT Data (RMC)

$GPRMC,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,<10>,<11>,<12>*hh<CR><LF>

<1> UTC time of position fix, hhmmss format
<2> Status, A = Valid position, V = NAV receiver warning
<3> Latitude, ddmm.mmmm format (leading zeros must be transmitted)
<4> Latitude hemisphere, N or S
<5> Longitude, dddmm.mmmm format (leading zeros must be transmitted)
<6> Longitude hemisphere, E or W
<7> Speed over ground: 000.0 to 999.9 knots (leading zeros will be transmitted)
<8> Course over ground, 000.0 to 359.9 degrees, true (leading zeros will be transmitted)
<9> UTC date of position fix, ddmmyy format

<10> Magnetic variation, 000.0 to 180.0 degrees (leading zeros will be transmitted)
<11> Magnetic variat i on di recti o n, E or W (westerly variation adds to true course)
<12> Mode indicator (only output if NMEA 0183 version 2.30 active), A = Autonomous,

D = Differential, E = Estimated, N = Data not valid

190-00880-00 GPS 20x Technical Specifications Rev. A

Page 9

3.1.7 Sensor Status Information (PGRMT)

The Garmin Proprietary sentence $PGRMT gives information concerning the status of the GPS sensor. This
sentence is transmitted once per minute regardless of the selected baud rate.

$PGRMT,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>*hh<CR><LF>

<1> Product, model and software version (variable length field, for example, “GPS 20x VER 2.05”)
<2> No Effect (This field is not used on this model and is included only for backwards compatibility)
<3> No Effect (This field is not used on this model and is included only for backwards compatibility)
<4> No Effect (This field is not used on this model and is included only for backwards compatibility)
<5> No Effect (This field is not used on this model and is included only for backwards compatibility)
<6> No Effect (This field is not used on this model and is included only for backwards compatibility)
<7> No Effect (This field is not used on this model and is included only for backwards compatibility)
<8> No Effect (This field is not used on this model and is included only for backwards compatibility)
<9> No Effect (This field is not used on this model and is included only for backwards compatibility)

190-00880-00 GPS 20x Technical Specifications Rev. A

Page 10

APPENDIX A: EARTH DATUM LIST

The following is a list of the Garmin GPS 20x Earth datum indices and the corresponding earth datum name
(including the area of application):

0 ADINDAN–Ethiopia, Mali, Senegal, Sudan
9 AUSTRALIAN GEODETIC 1984–Australia, Tasmania Island
10 ASTRO DOS 71/4–St. Helena Island
11 ASTRONOMIC STATION 1952–Marcus Island
12 ASTRO B4 SOROL ATOLL–Tern Island
13 BELLEVUE (IGN)–Efate and Erromango Islands
14 BERMUDA 1957–Bermuda Islands
15 BOGOTA OBSERVATORY–Colombia
16 CAMPO INCHAUSPE–Argentina
17 CANTON ASTRO 1966–Phoenix Islands
18 CAPE CANAVERAL–Florida, Bahama Islands
19 CAPE–South Africa
20 CARTHAGE–Tunisia
21 CHATHAM 1971–Chatham Island (New Zealand)
22 CHUA ASTRO–Paraguay
23 CORREGO ALEGRE–Brazil
24 DJAKARTA (BATAVIA)–Sumatra Island (Indonesia)
25 DOS 1968–Gizo Island (New Geor gi a Isl a n ds)
26 EASTER ISLAND 1967–Easter Island
27 EUROPEAN 1950–Austria, Belgium, Denmark, Finland, France, Germany, Gibraltar, Greece, Italy,

Luxembourg, Netherlands, Norway, Portu ga l , Spai n, Sweden, Switzerland
28 EUROPEAN 1979–Austria, Finland, Netherlands, Norway, Spain, Sweden, Switzerland
29 FINLAND HAYFORD 1910–Finland
30 GANDAJIKA BASE–Republic of Maldives
31 GEODETIC DATUM 1949–New Zealand
32 ORDNANCE SURVEY OF GREAT BRITAIN 1936–England, Isle of Man, Scotland, Shetland Islands,

Wales
33 GUAM 1963–Guam Island
34 GUX 1 ASTRO–Guadalcanal Island
35 HJORSEY 1955–Iceland
36 HONG KONG 1963–Hong Kong
37 INDIAN–Bangladesh, India, Nepal
38 INDIAN–Thailand, Vietnam
39 IRELAND 1965–Ireland
40 ISTS O73 ASTRO 1969–Diego Garcia
41 JOHNSTON ISLAND 1961–Johnston Island
42 KANDAWALA–Sri Lanka
43 KERGUELEN ISLAND–Kerguelen Island
190-00880-00 GPS 20x Technical Specifications Rev. A

Page 11

44 KERTAU 1948–West Malaysia, Singapore
45 L.C. 5 ASTRO–Cayman Brac Island
46 LIBERIA 1964–Liberia
47 LUZON–Mindanao Island
48 LUZON–Phillippines (excluding Mindanao Island)
49 MAHE 1971–Mahe Island
50 MARCO ASTRO–Salvage Islands
51 MASSAWA–Eritrea (Ethiopia)
52 MERCHICH–Morocco
53 MIDWAY ASTRO 1961–Midway Islan d
54 MINNA–Nigeria
55 NORTH AMERICAN 1927–Alaska
56 NORTH AMERICAN 1927–Bahamas (excluding San Salvador Island)
57 NORTH AMERICAN 1927–Central America (Belize, Costa Rica, El Salvador, Guatemala, Honduras,

Nicaragua)
58 NORTH AMERICAN 1927–Canal Zone
59 NORTH AMERICAN 1927–Canada (including Newfoundland Island)
60 NORTH AMERICAN 1927–Caribbean (Barbados, Caicos Islands, Cuba, Dominican Republic, Grand

Cayman, Jamaica, Leeward Islands, Turks Islands)
61 NORTH AMERICAN 1927–Mean Value (CONUS)
62 NORTH AMERICAN 1927–Cuba
63 NORTH AMERICAN 1927–Greenland (Hayes Peninsula)
64 NORTH AMERICAN 1927–Mexico
65 NORTH AMERICAN 1927–San Salvador Island
66 NORTH AMERICAN 1983–Alaska, Canada, Central America, CONUS, Mexico
67 NAPARIMA, BWI–Trinidad and T obago
68 NAHRWAN–Masirah Island (Oman)
69 NAHRWAN–Saudi Arabia
70 NAHRWAN–United Arab Emirates
71 OBSERVATORIO 1966–Corvo and Flores Islands (Azores)
72 OLD EGYPTIAN–Egypt
73 OLD HAWAIIAN–Mean Value
74 OMAN–Oman
75 PICO DE LAS NIEVES–Canary Islands
76 PITCAIRN ASTRO 1967–Pitcairn Island
77 PUERTO RICO–Puerto Rico, Virgin Islands
78 QATAR NATIONAL–Qatar
79 QORNOQ–South Greenland
80 REUNION–Mascarene Island
81 ROME 1940–Sardinia Island
82 RT 90–Sweden

190-00880-00 GPS 20x Technical Specifications Rev. A

Page 12

83 PROVISIONAL SOUTH AMERICAN 1956–Bolivia, Chile, Colombia, Ecuador, Guyana, Peru, V en e zuela
84 SOUTH AMERICAN 1969–Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Guyana, Paraguay,

Peru, Venezuela, Trinidad and Tobago
85 SOUTH ASIA–Singapore
86 PROVISIONAL SOUTH CHILEAN 1963–South Chile
87 SANTO (DOS)–Espirito Santo Island
88 SAO BRAZ–Sao Miguel, Santa Maria Islands (Azores)
89 SAPPER HILL 1943–East Falkland Island
90 SCHWARZECK–Namibia
91 SOUTHEAST BASE–Porto Santo and Madeira Islands
92 SOUTHWEST BASE–Faial, Graciosa, Pico, Sao Jorge, and Terceira Islands (Azores)
93 TIMBALAI 1948–Brunei and East Malaysia (Sarawak and Sabah)
94 TOKYO–Japan, Korea, Okinawa
95 TRISTAN ASTRO 1968–Tristan da Cunha
96 User defined earth datum
97 VITI LEVU 1916–Viti Levu Island (Fiji Islands)
98 WAKE-ENIWETOK 1960–Marshall Islands
99 WORLD GEODETIC SYSTEM 1972
100 WORLD GEODETIC SYSTEM 19 84
101 ZANDERIJ–Surinam
102 CH-1903–Switzerland
103 Hu-Tzu-Shan
104 Indonesia 74
105 Austria
106 Potsdam
107 Taiwan–modified Hu-Tzu-Shan
108 GDA–Geocentric Datum of Australia
109 Dutch

190-00880-00 GPS 20x Technical Specifications Rev. A

Page 13

APPENDIX B: GARMIN BINARY OUTPUT FORMAT

In Binary Output mode, GPS 20x will transmit packets once per second. The records must be enabled by commands
to the unit. Refer to the Garmin Device Interface Specification found in the Garmin Device Interface SDK
details on how to form and parse Garmin packets over USB. At the time of this printing, this document is located on
the Garmin Web site at:
decimal to signify that the record is a command. The data portion of the packet should be one of the following:

Note that the satellite data information is also enabled when the position record is enabled.
USB packets contain a header with a USB transport ID, a record ID, and the size of the record data in bytes.

Immediately following the header is the record data payload. Refer to the Garmin Device Interface Specification
found in the Garmin Device Interface SDK for details on how to form and parse Garmin USB packets.

USB Packet:

- 0x## 0x00 0x00 0x00 (USB transport ID, 1 byte unsigned, 4 bytes reserve d)

- 0x## 0x## 0x00 0x00 (Record ID, 2 bytes unsigned, 4 bytes reserved)

- 0x## 0x## 0x## 0x## (Number of data bytes in record, 4 bytes unsigne d )

- record data payload

www.garmin.com/support/commProtocol.html. The ID of each command should be 10

Function Command (base 10)

Position Record On 49

Position Record Off 50

for

All unused reserved bytes in the header must be zero.
The data bytes of each packet contain the record specified by the record ID. A description of each record follows.

190-00880-00 GPS 20x Technical Specifications Rev. A

Page 14

Satellite Data Record

The satellite data has a record ID of 0x72 with 84 (0x54) data bytes. The data bytes contain data for 12 satellites as
described below.

typedef struct
{
uint8 svid; //space vehicle identification (1–32 and 33–64 for WAAS)
uint16 snr; //signal-to-noise ratio
uint8 elev; //satellite elevation in degrees
uint16 azmth; //satellite azimuth in degrees
uint8 status; //status bit-field
} cpo_sat_data;

The status bit field represents a set of booleans described below:

Bit Meaning when bit is one (1)

0 The unit has ephemeris data for the specified satellite.
1 The unit has a differential correction for the specified satellite.
2 The unit is using this satellite in the solution.

This pattern is repeated for 12 satellites for a total of 12 X 7 bytes = 84 (0x54) bytes.
The USB Packet for the Satellite Record looks like:

- 0x14 0x00 0x00 0x00 (USB Transport ID, 1 byte unsigned, 4 bytes reserved)

- 0x72 0x00 0x00 0x00 (Record ID, 2 bytes unsigned, 4 bytes reserved)

- 0x54 0x00 0x00 0x00 (Number of data bytes, 4 bytes unsigned)

- 12 cpo_sat_data records

190-00880-00 GPS 20x Technical Specifications Rev. A

Page 15

Position Record

The Position Record has a record identifier of

typedef struct
{
float alt;
float epe;
float eph;
float epv;
int fix;
double gps_tow;
double lat;
double lon;
float lon_vel;
float lat_vel;
float alt_vel;
float msl_hght;
int leap_sec;
long grmn_days;
} cpo_pvt_data;

alt Ellipsoid altitude (meters)
epe Estimated position error (meters)
eph Position error, horizontal (meters)
epv Position error, vertical (meters)
fix 0 = no fix; 1 = no fix; 2 = 2D; 3 = 3D; 4 = 2D differential; 5 = 3D differential;
6 and greater = not defined
gps_tow GPS time of week (sec)
lat Latitude (radians)
lon Longitude (radians)
lon_vel Longitude velocity (meters/second)
lat_vel Latitude velocity (meters/second)
alt_vel Altitude velocity (meters/second)
msl_hght Height (mean sea level) (meters)
leap_sec UTC leap seconds
grmn_days Garmin days (days since December 31, 1989)

For the latest free software updates (excluding map data) throughout the life of your

Garmin products, visit the Garmin Web site at

www.garmin.com.

© 2008 Garmin Ltd. or its subsidiaries

Garmin International, Inc.

st

1200 East 151

Street, Olathe, Kansas 66062, U.S.A.

Garmin (Europe) Ltd.

Liberty House, Hounsdown Business Park, Southampton, Hampshire, SO40 9RB, U.K.

Garmin Corporation

nd

No. 68, Jangshu 2

Road, Shijr, Taipei County, Taiwan

www.garmin.com

Part Number 190-00880-00 Rev. A

190-00880-00 GPS 20x Technical Specifications Rev. A

Page 16