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DGPS:

How It Works

DGPS: How It Works

Differential GPS (DGPS) is a technique used to

improve the accuracy of the Global Positioning System.
DGPS reduces the effects of ionospheric variations and
can improve position accuracy typically to 1-5 meters.

The DGPS Beacon Transmitter is placed at a known

location (i.e., the exact position of the site has been
previously determined). At the beacon transmitter site,
the GPS satellites are monitored using a GPS receiver.
This receiver is equipped to calculate corrections for each
satellite received. The correction is the difference between
the distance to the satellite (from the beacon site) as
measured by the GPS receiver, and the actual distance to
the satellite based on the known location of the beacon
site. These corrections are communicated to the DGPS 53
through the DGPS Beacon Station. The DGPS 53 then
uses the corrections to remove errors from its own
measurements.

Satellites received by the DGPS 53, but not by the

GPS receiver at the beacon transmitter site, will not have
corresponding corrections. When four or more satellites
received by the DGPS 53 have corresponding corrections,
the result is a highly accurate position reading. The more
satellites with corrections, the more accurate the position.

The DGPS 53 receives RTCM SC-104 format signals

from ground based DGPS Beacon Stations operating in
the 283.5 kHz to 325.0 kHz frequency band and data
rates of 25, 50, 100, or 200 bits per second. These
stations are typically operated by government agencies
such as the U.S. Coast Guard.

Generally, the closest DGPS station will provide the

most accurate correction data. Individual stations vary
and the user may wish to verify the suitability of the
signal for the intended application with the station
operator. The station power is normally set to provide a
usable range somewhere near 300 km. Other factors such
as local interference, lightning, time of day and season,
and if the path to the station is over ground or water, and
antenna selection or installation affect the usable signal
range.

Reference

F

The DGPS 53 has the GPS
and DGPS receivers
combined within the same
housing.

www.reelschematic.com

www.reelschematic.com

Содержание DGPS 53

Страница 1: ...owner s manual and reference guide DGPS 53 integrated GPS DGPS receiver DGPS53Cover p65 8 29 00 11 10 AM 1 www reelschematic com www reelschematic com ...

Страница 2: ...orage medium to be viewed for personal use provided that such electronic or printed copy of this manual contains the complete text of this copyright notice and provided further that any unauthorized commercial distribution of this manual is strictly prohibited Information in this manual is subject to change without notice GARMIN Corporation reserves the right to change or improve its products and ...

Страница 3: ... 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 To obtain warranty service contact your GARMIN dealer or call the GARMIN Customer Service department 913 397 8200 for a returned merchandise tracking number The unit should be securely packaged with the tracking number clearly marked on the outsid...

Страница 4: ...nt Although a GPS DGPS system is a precision electronic NAVigation AID NAVAID any NAVAID can be misused or misinterpreted and therefore become unsafe Use the GPS DGPS system at your own risk To reduce this risk carefully review and understand all aspects of this Owner s Manual and carefully compare indications from your display to all available navigation sources including the information from oth...

Страница 5: ...ts 5 Installation Mounting the DGPS 53 6 7 Connecting DGPS 53 8 9 Operation Using the DGPS 53 10 NMEA Sentences 11 18 One Pulse Per Second Output 18 Reference GPS How It Works 19 DGPS How It Works 20 Sources of Error 21 22 Troubleshooting Chart 23 DGPS 53 Specifications 24 Appendix A Earth Datums 25 27 Index 28 www reelschematic com www reelschematic com ...

Страница 6: ... Notification of Product Updates Notification of New Products Lost or Stolen unit tracking H The GARMIN DGPS 53 has no user serviceable parts Should you ever encounter a problem with your unit please contact your GARMIN dealer or GARMIN Customer Service 913 397 8200 or 800 800 1020 for repairs Repairs should only be made by an authorized GARMIN service center Unauthorized repairs or modifications ...

Страница 7: ...mit navigation data Convenience May be remotely mounted in an out of the way location Receiver status information is displayed directly on the chartplotter or PC Low Power Consumption Draws approximately 170 milliamps during normal operation Accuracy 1 5 2DRMS meters typical Package Contents Your GARMIN DGPS 53 package includes DGPS 53 unit 30 Power Data Cable Owner s Manual Reference Guide Beacon...

Страница 8: ...Part number 010 10284 00 It is recommended that the system be temporarily hooked up with the wiring and the unit placed at the desired installation location Then check operation with potential interfering equipment turned on and off For example other electronic equipment fan motors engine ignition alternators generators radars and VHF radio transmissions can be sources of interference Position the...

Страница 9: ...ower data cable and DGPS 53 connector and push the connector in until it seats Turn the locking ring clockwise until the power data cable is firmly locked into position 4 Route the power data cable from the DGPS 53 to the GPS unit Excess cable may be shortened or coiled together and secured in an inconspicuous location If additional cable is needed you may use GARMIN s optional 60 cable 010 10284 ...

Страница 10: ...nal as the GPS unit no additional connection is required unless a separate RETURN line is provided by the GPS unit 4 Connect the RED wire from the power data cable to a 8 35 VDC power source 5 If a remote power switch is being installed reference Figure 5 for wiring the switch This will allow the DGPS 53 to remain connected to a power source but manually powered on and off Otherwise if the receive...

Страница 11: ... the DGPS 53 DGPS 53 Chartplotter Connection 7 6 1 2 4 3 5 DGPS 53 7 YELLOW PPS 6 GREEN DGPS STATUS LED 5 WHITE REMOTE ON OFF 1 RED 8 35 VDC 2 BLACK GROUND 4 BROWN DATA IN GROUND 3 BLUE DATA OUT DATA OUT DATA IN Power Data Cable 8 35VDC Chartplotter Fuse 2 6A Power Data Cable Figure 4 Wiring a DB9 Serial Connector To the DGPS 53 Figure 5 Wiring a Remote Power Switch For the DGPS 53 DGPS 53 8 35 VD...

Страница 12: ...PC or other compatible source The DGPS 53 should tune into a DGPS station within about 10 minutes The unit will store the last used frequency in non volatile memory and default to that frequency on next use If you lose DGPS signal the unit will attempt to reconnect to the last frequency and if necessary tune to another station Interfaces The DGPS 53 interface protocol design is based on the Nation...

Страница 13: ...fter any data field and valid fields up to that point will be acted on by the DGPS 53 Almanac Information ALM GPALM 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 hh CR LF The GPALM sentence can be used to replace the DGPS 53 s stored almanac information if battery back up has failed 1 Total number of ALM sentences to be transmitted by the sensor board during almanac download This field can be null or any nu...

Страница 14: ...lues Current default values can also be obtained by sending PGRMCE to the board PGRMC 1 2 3 4 5 6 7 8 9 10 11 12 13 14 hh CR LF 1 Fix mode A automatic 2 2D exclusively host must supply altitude 3 3D exclusively 2 Altitude above below mean sea level 1500 0 to 18000 0 meters 3 Earth datum index If the user datum index 96 is specified fields 4 through 8 must contain valid values Otherwise fields 4 th...

Страница 15: ...pty field is allowed e g PGRMO 3 or the mode field may contain from 1 to 5 characters 2 If the target sentence mode is 0 disable or 1 enable the target sentence description field must be an identifier for one of the sentences being output by the DGPS 53 3 If either the target sentence mode field or the target sentence description field is not valid the PGRMO sentence will have no effect 4 PGRMO GP...

Страница 16: ...d Universal Time date and time of day in the transmitted sentences Prior to the initial position fix the date and time of day are provided by the on board clock After the initial position fix the date and time of day are calculated using GPS satellite information and are synchronized with the one pulse per second output The DGPS 53 uses information obtained from the GPS satellites to add or delete...

Страница 17: ... 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 GPS Satellites in View GSV GPGSV 1 2 3 4 5 6 7 4 5 6 7 hh CR LF 1...

Страница 18: ...h GPS Talker ID VTG The GPVTG sentence reports track and velocity information with a checksum GPVTG 1 T 2 M 3 N 4 K 5 hh CR LF 1 True course over ground 000 to 359 degrees leading zeros will be transmitted 2 Magnetic course over ground 000 to 359 degrees leading zeros will be transmitted 3 Speed over ground 000 0 to 999 9 knots leading zeros will be transmitted 4 Speed over ground 0000 0 to 1851 8...

Страница 19: ...error EPE 0 0 to 999 9 meters GPS Fix Data Sentence PGRMF The sentence PGRMF is GARMIN Proprietary format reporting time position speed and course information PGRMF 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 hh CR LF 1 GPS week number 0 1023 2 GPS seconds 0 604799 3 UTC date of position fix ddmmyy format 4 UTC time of position fix hhmmss format 5 GPS leap second count 6 Latitude ddmm mmmm format leading ...

Страница 20: ...acon bit rate 0 25 50 100 or 200 bps 3 Beacon SNR 0 to 31 4 Beacon data quality 0 to 100 5 Distance to beacon reference station in kilometers One Pulse Per Second Output The highly accurate within 1ms one pulse per second PPS output is provided for applications requiring precise timing measurements The signal is generated after the initial position fix has been calculated and continues until power...

Страница 21: ...mation for that satellite and for every other satellite in the system Each satellite transmits a message which essentially says I m satellite X my position is currently Y and this message was sent at time Z Of course this is a gross oversimplification but you get the idea The GPS receiver reads the message and saves the data for continual use Now to determine your position the GPS receiver compare...

Страница 22: ...beacon transmitter site will not have corresponding corrections When four or more satellites received by the DGPS 53 have corresponding corrections the result is a highly accurate position reading The more satellites with corrections the more accurate the position The DGPS 53 receives RTCM SC 104 format signals from ground based DGPS Beacon Stations operating in the 283 5 kHz to 325 0 kHz frequenc...

Страница 23: ...erstorm activity Other sources of interference such as alternator motors ignition systems and VHF can also affect signal reception Alternator ignition interference can be minimized through proper shielding of the ship s wiring by using an EMI RFI filter and by mounting the beacon receiver s antenna away from these sources of interference Multipath Multipath error occurs when the GPS signal is refl...

Страница 24: ... from the DGPS broadcast station Satellite Geometry A minimum of 4 satellites are required to determine a 3D position At times additional satellites are required due to their placement with respect to each other This relative placement is referred to as satellite geometry Ideal satellite geometry exists when the satellites are located at wide angles with respect to each other When satellites are l...

Страница 25: ... Accuracy not as expected Poor satellite geometry exists or too few satellites are visible Interference to GPS antenna and or beacon antenna exists Multipath signals being received by GPS unit Too far from DGPS transmitter or not tuned to closest station Possible Cause Problem 3 No output from DGPS 53 Unit not wired properly Check wiring Receiving device not properly configured www reelschematic c...

Страница 26: ...t Keying MSK Bit Rates 25 50 100 200 bps Interfaces Input RS 232 or NMEA 0183 4800 baud Input Sentences Binary Magnavox PSLIB Starlink Output RS 232 4800 baud Output Sentence RTCM SC 104 6 of 8 bit format NMEA 0183 version 2 0 Pulse Per Second One Pulse Per Second accuracy 1 microsecond at rising edge of PPS pulse DGPS 53 Specifications Complete information concerning NMEA RTCM formats and sentenc...

Страница 27: ...rromango 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 Georgia ...

Страница 28: ...Island 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...

Страница 29: ...ingapore 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 Ja...

Страница 30: ...rference 6 7 M Manual Tuning 13 Mounting the Receiver 6 9 N NMEA 10 24 NMEA Received Sentences 11 13 NMEA Transmited Sentences 14 18 O On Off Switch 6 8 9 One Pulse Per Second Output 18 Operation 10 18 P Package Contents 5 PC Connection 8 9 Power Data Cable 5 9 R Registration 4 RTCM SC 104 format 20 24 S Serial Number 4 Sources of Error 21 22 Sources of Interference 6 7 Specifications 24 T Table o...

Страница 31: ...DGPS53Cover p65 8 29 00 11 10 AM 3 www reelschematic com www reelschematic com ...

Страница 32: ...2 U S A GARMIN Europe Ltd Unit 5 The Quadrangle Abbey Park Industrial Estate Romsey SO51 9AQ U K GARMIN Asia Corporation No 68 Jangshu 2nd Rd Shijr Taipei County Taiwan www garmin com Part Number 190 00194 00 Rev A DGPS53Cover p65 8 29 00 11 10 AM 4 www reelschematic com www reelschematic com ...

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