GPS 18 TECHNICAL SPECIFICATIONS Garmin International, Inc. 1200 E. 151st Street Olathe, KS 66062 USA 190-00307-00, Revision D June 2005 GPS 18 Technical Specifications (190-00307-00) Rev.
© Copyright 2004–2005 Garmin Ltd. or its subsidiaries All Rights Reserved Except as expressly provided below, 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.
TABLE OF CONTENTS 1 Introduction..................................................................................................................1 1.1 Cautions ............................................................................................................................................1 1.2 Limited Warranty ..............................................................................................................................2 1.3 Features ..............................................
4.2.9 4.2.10 4.2.11 4.2.12 4.2.13 4.2.14 Geographic Position (GLL)..............................................................................................................18 Estimated Error Information (PGRME) ...........................................................................................19 GPS Fix Data Sentence (PGRMF) ...................................................................................................19 Sensor Status Information (PGRMT) ....................................
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 18 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 18.
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.
Overview The GPS 18 series products include an embedded receiver and an antenna. Based on the proven technology found in other Garmin 12-channel GPS receivers, the GPS 18 tracks up to 12 satellites at a time while providing fast time-to-first-fix, precise navigation updates (five times per second for the GPS 18-5Hz, and once per second for the GPS 18 USB, 18 PC, and 18 LVC), and low power consumption.
1.4 GPS 18 SERIES There are several different versions of GPS 18 available. Refer below for a list of the three major divisions of the GPS 18 Series. 1.4.1 GPS 18 USB The GPS 18 USB interfaces to a computer with an available USB port. Drivers are available for use on Windows computers. Macintosh and Linux drivers are not available. 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.
1.5 TECHNICAL SPECIFICATIONS Specifications are subject to change without notice. 1.5.1 Physical Characteristics 1.5.1.1 Size 61 mm in diameter and 19.5 mm in height 1.5.1.2 Weight • GPS 18 unit only (no cable): 1.9 oz (53.9 g) • GPS 18 USB: 3.5 oz (100.4 g) • GPS 18 PC: 6.5 oz (184.6 g) • GPS 18 LVC (3 meter cable): 3.9 oz (110.6 g) • GPS 18 LVC-5m (5 meter cable): 5.7 oz (161.6 g) • GPS 18-5Hz (5 meter cable): 5.7 oz (161.6 g) 1.5.1.3 Color Black 1.5.1.
1.5.2.4 GPS Receiver Sensitivity -165 dBW minimum 1.5.3 Environmental Characteristics • Operating Temperature: -30°C to +80°C • Storage Temperature: 1.5.4 -40°C to +90°C GPS Performance 1.5.4.1 Receiver WAAS enabled; 12 parallel channel GPS receiver continuously tracks and uses up to 12 satellites (up to 11 with Measurement Pulse Output active) to compute and update your position. 1.5.4.2 Acquisition Times • Reacquisition: Less than 2 seconds • Warm: Approx.
1.5.5 Interfaces 1.5.5.1 GPS 18 Electrical Characteristics • GPS 18 USB: USB 2.0 full-speed protocol compatible, as well as USB 1.1 full-speed protocol. • GPS 18 PC and LVC: TIA-232-F (RS-232) compatible asynchronous receiver. Default setting is 4800 baud. • GPS 18-5Hz: TIA-232-F (RS-232) compatible asynchronous receiver. Default setting is 19200 baud. 1.5.5.2 Garmin Interface and Garmin USB Protocol Refer to the Garmin Device Interface Specification for information about the Garmin USB Protocol.
2 GPS 18 LVC & GPS 18-5Hz WIRING AND PINOUTS The GPS 18 LVC/18-5Hz interfaces to a serial port. The unit accepts TIA-232-F (RS-232) level inputs and transmits voltage levels from ground to the input voltage, TIA-232-F (RS-232) polarity. The GPS 18 LVC/18-5Hz wires are terminated with a six-wire connector that is used by Garmin for testing purposes. You can remove this connector without voiding your warranty (see Section 1.2 Limited Warranty). 2.
Figure 2. PDA Serial Port Interconnection Figure 3. Basic NMEA Device Interconnection GPS 18 Technical Specifications (190-00307-00) Rev.
3 MECHANICAL CHARACTERISTICS & MOUNTING The central threaded recess accepts a metric M3 threaded bolt. The recess is approximately 4 mm deep (4.32 +/- 0.08 mm). The following drawings show example geometries for mounting hardware in case you wish to design your own custom mount. Figure 5 shows mounting geometry for a mount formed from steel sheet metal that is 1.15 mm thick. Figure 7 shows similar mounting geometry for mount formed from aluminum sheet metal that is 1.25 mm thick.
Figure 5. GPS 18 Suction Cup Mount Center Hole Dimensions Figure 6. GPS 18 Flush Mount Dimensions Figure 7. GPS 18 Flush Mount Center Hole Dimensions GPS 18 Technical Specifications (190-00307-00) Rev.
4 GPS 18 PC, GPS 18 LVC, & GPS 18-5Hz SOFTWARE INTERFACE The interface protocol design of the GPS 18 PC, LVC, and GPS 18-5Hz products is based on the National Marine Electronics Association’s NMEA 0183 ASCII interface specification. This standard is fully defined in NMEA 0183, Version 2.30. Copies may be obtained from NMEA, www.nmea.org.
4.1.2 Sensor Initialization Information (PGRMI) The $PGRMI sentence provides information used to initialize the GPS sensor’s set position and time used for satellite acquisition. Receipt of this sentence by the GPS sensor causes the software to restart the satellite acquisition process. If there are no errors in the sentence, it will be echoed upon receipt. If an error is detected, the echoed PGRMI sentence will contain the current default values.
4.1.4 Additional Sensor Configuration Information (PGRMC1) The $PGRMC1 sentence provides additional information used to configure the GPS sensor operation. Configuration parameters are stored in non-volatile memory and retained between power cycles. The GPS sensor will echo this sentence upon its receipt if no errors are detected. If an error is detected, the echoed PGRMC1 sentence will contain the current default values. Current default values can also be obtained by sending $PGRMC1E to the GPS sensor.
4.2 TRANSMITTED NMEA 0183 SENTENCES The subsequent paragraphs define the sentences that can be transmitted by the GPS 18 PC and LVC. 4.2.1 Sentence Transmission Rate Sentences are transmitted with respect to the user selected baud rate. The GPS sensor will transmit each sentence (except where noted in particular transmitted sentence descriptions) at a periodic rate based on the user selected baud rate and user selected output sentences. The GPS sensor will transmit the selected sentences contiguously.
4.2.2 Transmitted Time The GPS sensor outputs UTC (Coordinated Universal Time) 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 18-5Hz outputs a UTC with a tenths-of-a-second precision: 123456.8, for example.
4.2.4 Global Positioning System Fix Data (GGA) $GPGGA,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,M,<10>,M,<11>,<12>*hh <1> <2> <3> <4> <5> <6> <7> <8> <9> <10> <11> <12> 4.2.5 UTC time of position fix, hhmmss format for GPS 18 PC or LVC; hhmmss.s format for GPS 185Hz Latitude, ddmm.mmmm format for GPS 18 PC/LVC; ddmm.mmmmm for GPS 18-5Hz (leading zeros will be transmitted) Latitude hemisphere, N or S Longitude, dddmm.mmmm format for GPS 18 PC/LVC; dddmm.
4.2.7 Recommended Minimum Specific GPS/TRANSIT Data (RMC) $GPRMC,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,<10>,<11>,<12>*hh <1> <2> <3> <4> <5> <6> <7> <8> <9> <10> <11> <12> 4.2.8 UTC time of position fix, hhmmss format for GPS 18 PC/LVC; hhmmss.s format for GPS 18-5Hz Status, A = Valid position, V = NAV receiver warning Latitude, ddmm.mmm format for GPS 18 PC/LVC; ddmm.mmmmm format for GPS 18-5Hz (leading zeros must be transmitted) Latitude hemisphere, N or S Longitude, ddmm.
4.2.10 Estimated Error Information (PGRME) $PGRME,<1>,M,<2>,M,<3>,M*hh <1> <2> <3> Estimated horizontal position error (HPE), 0.0 to 999.9 meters Estimated vertical position error (VPE), 0.0 to 999.9 meters Estimated position error (EPE), 0.0 to 999.9 meters 4.2.
4.2.14 DGPS Beacon Information (PGRMB) NOTE: The GPS 18 products do not support PGRMB at this time. $PGRMB,<1>,<2>,<3>,<4>,<5>,K,<6>,<7>,<8>*hh <1> <2> <3> <4> <5> <6> <7> <8> 4.3 Beacon tune frequency, 0.0, 283.5 to 325.0 kHz in 0.
The default pulse width is 100 ms, however; it may be programmed in 20 ms increments between 20 ms and 180 ms as described in $PGRMC Section 4.1.2 Sensor Initialization Information (PGRMI), field <13>.
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 44 KERTAU 1948–West Malaysia, Singapore 45 L.C.
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 83 PROVISIONAL SOUTH AMERICAN 1956–Bolivia, Chile, Colombia, Ecuador, Guyana, Peru, Venezuela 84 SOUTH AMERICAN 1969–Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Guyana, Paraguay, Peru, Venezuela, T
APPENDIX B: BINARY PHASE OUTPUT FORMAT In binary phase output mode, GPS 18 series products will transmit two types of packets once per second. One record contains primarily post-process information such as position and velocity information. The second record contains receiver measurement information. For the GPS 18 PC, GPS 18 LVC, and GPS 185Hz, the records are sent at a default baud rate of 9600 baud, 8 data bits, and no parity.
Satellite Data Record The satellite data has a record ID of 0x72 with 84 (0x54) data bytes. The data bytes contain the data for the 12 channels as described below.
The USB Packet for the Satellite Record looks like: - 0x72 (Record ID – single byte) - 0x54 (Number of data bytes – single byte) - cpo_all_sat_data 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 epe eph epv fix Ellipsoid altitude (meters) Est pos error (meters) Pos err, h
Receiver Measurement Record typedef struct { unsigned long double unsigned int char unsigned char char char } cpo_rcv_sv_data; typedef struct { double int cpo_rcv_sv_data } cpo_rcv_data; rcvr_tow rcvr_wn cycles pr phase slp_dtct snr_dbhz svid numbers. valid cycles; pr; phase; slp_dtct; snr_dbhz; svid; valid; rcvr_tow; rcvr_wn; sv[ 12 ]; Receiver time of week (seconds) Receiver week number Number of accumulated cycles Pseudorange (meters) To convert to (0 to 359.999) multiply by 360.0 and divide by 2048.
DLE and ETX bytes: Sample C code to receive the two records should filter DLE and ETX bytes as described below: typedef enum { DAT, DLE, ETX } rx_state_type; /* Declare and initialize static variables */ static char in_que[ 256 ]; static int in_que_ptr = 0; static rx_state_type rx_state = DAT; . . .
APPENDIX C: CHANGING THE BAUD RATE IN GARMIN MODE In certain cases, you may need to change the default baud rate of your Garmin GPS receiver while in Garmin mode. Follow these steps to temporarily change the baud rate. Refer to the Garmin Device Interface Specification for details on how to form and parse Garmin packets. At the time of this printing, these specs are available from the technical suppport section of our Web site: http://www.garmin.com/support/commProtocol.html. 1.
APPENDIX D: GPS 18 PC/ LVC/18-5Hz & WINDOWS SERIAL MOUSE ISSUE Problem: It is possible for Windows to incorrectly interpret the NMEA 0183 output of the GPS 18 PC as the output of a Microsoft Serial BallPoint Mouse. When that happens, Windows loads drivers for the Serial BallPoint Mouse. This causes the cursor to move erratically about the display, clicking, right clicking, double clicking, dragging and dropping displayed items as it goes.
4. Select the Serial Port to which the GPS 18 is connected. Select Auto to have the program automatically determine the Baud Rate, or select Manual to manually select the Baud Rate of the GPS 18. Click OK when done. 5. Click the Connect icon , or select Comm > Connect to connect to the GPS 18. 6. To view the current programming of the GPS 18, select Config > Get Configuration from GPS (or press the F8 key). The current programming of the GPS 18 is displayed in the window, as shown on the previous page.
APPENDIX E: SENSOR CONFIGURATION SOFTWARE SNSRCFG configures the GPS sensors based on user-selected parameters. Some application features include the ability to download GPS sensor configuration, maintain different configurations in files, and perform GPS sensor configurations quickly with the use of one function key. This section provides a brief overview of the Sensor Configuration Software. Refer to this section when using the software to configure your Garmin sensor.
File Menu The File Menu allows you to open, save, and print sensor configurations. The items in the File Menu work like most Windows-based programs. Comm Menu The Comm (Communication) Menu allows you to set the port number, baud rate, and then connect and disconnect from the sensor. Setup: Opens the Comm Setup Window, shown to the left. Select the Serial Port to which the sensor is connected from the dropdown list.
Get Configuration From GPS (F8): Retrieves the current programming from the sensor. The programming is then displayed in the Main Interface Window. Send Configuration To GPS (F9): Sends the changes you have made to the programming to the sensor. Switch to NMEA Mode (F10): Switches the unit to NMEA Mode. The sensor must be in NMEA Mode when connected to this software. Switch to Garmin Mode (F11): Switches the unit to Garmin Mode.
