Garmin GPS 35 LP Manual

GPS 35/36 TracPakTM
GPS SMART ANTENNA
TECHNICAL SPECIFICATION
GARMIN · 1200 E. 151st Street · Olathe, Kansas 66062 ·
[phone] · [phone] FAX

©1999GARMINCorporation,1200E.151stStreet,Olathe,
KS 66062
Allrightsreserved. Nopartofthismanualmaybereproduced
or transmitted in any form or by any means, electronic or
mechanical,includingphotocopyingandrecording,forany
purposewithouttheexpresswrittenpermissionofGARMIN.
Information in this document is subject to change without
notice. GARMIN reserves the right to change or improve
their products and to make changes in the content without
obligation to notify any person or organization of such
changes or improvements.
January, 1999 190-00104-00 Rev. D

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 35/36 is a precision
electronic NAVigation AID (NAVAID), any NAVAID can be
misused or misinterpreted, and therefore become unsafe.
Use the GPS 35/36 at your own risk. To reduce the risk,
carefullyreviewandunderstandallaspectsofthisTechnical
Manual before using the GPS 35/36. When in actual use,
carefully compare indications from the GPS 35/36 to all
availablenavigationsourcesincludingtheinformationfrom
other NAVAIDs, visual sightings, charts, etc. For safety,
always resolve any discrepancies before continuing
navigation.
NOTE
This device has been tested and found to comply with the
limits for a Class B digital device, pursuant to Part 15 of the
FCC Rules. Operation is subject to the following two
conditions: (1) This device may not cause harmful
interference,and(2)thisdevicemustacceptanyinterference
received, including interference that may cause undesired
operation.
Thisdevicegenerates,usesandcanradiateradiofrequency
energyand,ifnotinstalledandusedinaccordancewiththe
instructions, may cause harmful interference to radio
communications. However, there is no guarantee that
interference will not occur in a particular installation. If this
devicedoescauseharmfulinterferencetoradioortelevision
reception, which can be determined by turning the device
off and on, you are encouraged to try to correct the
interference by one or more of the following measures:
· Reorient or relocate the receiving antenna.
· Increase the separation between this device and the
receiver.

· Connect this device to an outlet on a different circuit
than that to which the receiver is connected.
· Consult the dealer or an experienced radio/TV
technician for help.
This device contains no user-serviceable parts. Repairs
shouldonlybeperformedbyanauthorizedGARMINservice
center. Unauthorizedrepairsormodificationstothisdevice
could void your warranty and your authority to operate this
device under Part 15 regulations.

TABLE OF CONTENTS
1. Introduction 1
1.1 Overview 1
1.2 Features 2
1.3 Technical Specifications 2
1.4 Application 4
2. Operational Characteristics 5
2.1 Self Test 5
2.2 Initialization 5
2.3 Navigation 6
2.4 Satellite Data Collection 7
3. Hardware Interface 9
3.1 Mechanical Dimensions 9
3.2 Mounting Configurations and Options 11
3.3 Connection Wiring Description 15
4. Software Interface 17
4.1 NMEA Received Sentences 17
4.2 NMEA Transmitted Sentences 21
4.3 Baud Rate Selection 28
4.4 RTCM Received Data 29
A. Earth Datums A-1

SECTION 1
INTRODUCTION
1.1 OVERVIEW
The GARMIN GPS 35/36 is a complete GPS receiver,
including an embedded antenna, designed for a broad
spectrumofOEM(OriginalEquipmentManufacturer)system
applications. Based on the proven technology found in
other GARMIN 12 channel GPS receivers, the GPS 35/36
will track up to 12 satellites at a time while providing fast
time-to-first-fix, one second navigation updates and low
power consumption. Its far reaching capability meets the
sensitivity requirements of land navigation as well as the
dynamics requirements of high performance aircraft.
The GPS 35/36design utilizes the latest technology and
highlevelcircuitintegrationtoachievesuperiorperformance
whileminimizingspaceandpowerrequirements. Allcritical
components of the system including the RF/IF receiver
hardware and the digital baseband are designed and
manufactured by GARMIN to ensure the quality and
capability of the GPS 35/36. This hardware capability
combinedwithsoftwareintelligencemakes theGPS 35/36
easy to integrate and use.
The GPS 35/36 is designed to withstand rugged operating
conditionsand iscompletelywater resistant. TheGPS35/
36 is a complete GPS receiver that requires minimal
additional components be supplied by an OEM or system
integrator. AminimumsystemmustprovidetheGPS35/36
with a source of power and a clear view of the GPS
satellites. ThesystemmaycommunicatewiththeGPS35/
36 via a choice of two RS-232 compatible full duplex
communicationchannels. Internalmemorybackupallows
theGPS35/36toretaincriticaldatasuchassatelliteorbital
parameters,lastposition,dateandtime. Enduserinterfaces
1

suchaskeyboardsanddisplaysareaddedbytheapplication
designer.
1.2 FEATURES
TheGPS35/36providesahostoffeaturesthatmakeiteasy
to integrate and use.
1) Full navigation accuracy provided by Standard
Positioning Service (SPS)
2) Compact design ideal for applications with minimal
space
3) High performance receiver tracks up to 12 satellites
whileprovidingfastfirstfixandlowpowerconsumption
4) Differential capability utilizes real-time RTCM
corrections producing 3-10 meter position accuracy
5) Internalclockandmemoryaresustainedbyamemory
backup battery or optional external standby power
6) User initialization is not required
7) Navigation mode (2D or 3D) may be configured by
the user
8) Two communication channels and user selectable
baud rates allow maximum interface capability and
flexibility
1.3 TECHNICAL SPECIFICATIONS
Specifications are subject to change without notice.
1.3.1 PhysicalCharacteristics
1) Single construction integrated antenna/receiver.
2) Weight: 4.4 oz, (124.5 g), not including cable
3) Size: 2.230"(w)x 3.796" (l)x1.047" (h), (56.64mm
x 96.42 mm x 26.60 mm)
2

1.3.2 EnvironmentalCharacteristics
1) Operating temperature: -30°C to +85°C (internal
temperature)
2) Storage temperature: -40°C to +90°C
1.3.3 ElectricalCharacteristics
1) Input voltage: 10 to 30 VDC, unregulated.
2) Typically draws 150 mA @ 12 VDC
3) Backup power: Internal 3V Lithium coin cell battery,
up to 10 year life
1.3.4 Performance
1) Tracks up to 12 satellites
2) Update rate: 1 second
3) Acquisition time
- 15 seconds warm (all data known)
- 45 seconds cold (initial position, time and
almanac known, ephemeris unknown)
- 5.0 minutes AutoLocateTM (almanac known, initial
position and time unknown)
- 5 minutes search the sky (no data known)
4) Position accuracy:
Differential GPS (DGPS): 5 meters RMS
Non-differentialGPS: 15metersRMS(100meters
with Selective Availability on)
5) Velocityaccuracy: 0.2m/sRMSsteadystate(subject
to Selective Availability)
6) Dynamics: 999 knots velocity, 6g dynamics
3

1.3.5 Interfaces
1) DualchannelRS-232compatiblewithuserselectable
baud rate (1200, 2400, 4800, 9600)
2) NMEA 0183 Version 2.0 ASCII output (GPALM,
GPGGA, GPGSA, GPGSV, GPRMC, GPVTG,
PGRME, PGRMT, PGRMV, PGRMF, LCGLL,
LCVTG)
Inputs
- Initial position, date and time (not required)
- Earth datum and differential mode configuration
command, almanac.
Outputs
- Position, velocity and time
- Receiver and satellite status
- Differential Reference Station ID and RTCM Data
age
- Geometry and error estimates
3) Real-timeDifferentialCorrectioninput(RTCMformat)
1.4 APPLICATION
4
TYPICAL APPLICATION ARCHITECTURE

SECTION 2
OPERATIONAL CHARACTERISTICS
Thissectiondescribesthebasicoperationalcharacteristics
of the GPS 35/36. Additional information regarding input
and output specifications are contained in Section 4.
2.1 SELF TEST
After input power has been applied to the GPS 35/36 and
periodically thereafter, the unit will perform critical self test
functionsandreporttheresultsovertheoutputchannel(s).
The following tests will be performed:
1) RAM check
2) ROM test
3) Receiver test
4) Real-time clock test
5) Oscillator check
In addition to the results of the above tests, the GPS 35/36
will report software version information.
2.2 INITIALIZATION
Aftertheinitialselftestiscomplete,theGPS35/36willbegin
the process of satellite acquisition and tracking. The
acquisition process is fully automatic and, under normal
circumstances, will take approximately 45 seconds to
achieve a position fix (15 seconds if ephemeris data is
known). After a position fix has been calculated, valid
position, velocity and time information will be transmitted
over the output channel(s).
5

6
Like all GPS receivers, the GPS 35/36 utilizes initial data
such as last stored position, date and time as well as
satellite orbital data to achieve maximum acquisition
performance. If significant inaccuracy exists in the initial
data,oriftheorbitaldataisobsolete,itmaytake5.0minutes
toachieveanavigationsolution. TheGPS35/36AutolocateTM
featureiscapableofautomaticallydetermininganavigation
solutionwithoutinterventionfromthehostsystem. However,
acquisitionperformancecanbeimprovedifthehostsystem
initializestheGPS35/36followingtheoccurrenceofoneor
more of the following events:
1) Transportation over distances further than 1500
kilometers
2) Failureoftheinternalmemorybatterywithoutsystem
standby power
3) Stored date/time off by more than 30 minutes
See Section 4 for more information on initializing the GPS
35/36.
2.3 NAVIGATION
After the acquisition process is complete, the GPS 35/36
will begin sending valid navigation information over its
output channels. These data include:
1) Latitude/longitude/altitude
2) Velocity
3) Date/time
4) Error estimates
5) Satellite and receiver status
Normally the GPS 35/36 will select the optimal navigation
mode(2Dor3D)basedonavailablesatellitesandgeometry
considerations. Thehostsystem,atitsoption,maycommand

7
the GPS 35/36 to choose a specific mode of navigation,
such as 2D. The following modes are available:
1) 2D exclusively with altitude supplied by the host
system (altitude hold mode)
2) 3DexclusivelywithaltitudecomputedbytheGPS35/
36
3) Automatic mode in which the board set determines
thedesiredmodebasedonsatelliteavailabilityand
geometry considerations
When navigating in the 2D mode (either exclusive or
automatic),theGPS35/36utilizesthelastcomputedaltitude
or the last altitude supplied by the host system, whichever
is newer. The host system must ensure that the altitude
used for 2D navigation is accurate since the resulting
position error may be as large as the altitude error. See
Section 4 for more information on altitude control.
The GPS 35/36 will default to automatic differential
corrections,attemptingtoapplythemtothesatellitedata,in
order to produce a differential (DGPS) solution. The host
system,atitsoption,may alsocommand theGPS 35/36to
choose differential only mode. When navigating in the
differentialonly mode,theGPS 35/36 willoutput a position
only when a differential solution is available.
2.4 SATELLITE DATA COLLECTION
The GPS 35/36 will automatically update satellite orbital
data as it operates. The intelligence of the GPS 35/36
combined with its hardware capability allows these data to
be collected and stored without intervention from the host
system. A few key points should be considered regarding
this process:
1) IftheGPS 35/36isnotoperatedfor aperiodofsix(6)
monthsormore, theunitwill“searchthe sky”inorder
tocollect satelliteorbitalinformation. This process is

fullyautomaticand,undernormalcircumstances,will
takeabout5minutestoachieveanavigationsolution.
However, the host system should allow the GPS 35/
36toremainonforatleast12.5minutesafterthefirst
satelliteisacquired(seeSection4formoreinformation
on status indications).
2) If the internal memory backup battery fails or is not
installed while the host system power is off and not
connected to standby power, the GPS 35/36 will
search the sky as described above. The system
designershouldbeawareoftheavailabilityofstandby
powerinputtotheGPS35/36topreventthissituation.
3) If the initial data is significantly inaccurate, the GPS
35/36 will perform an operation known as
AutoLocateTM. Thisprocedureis fullyautomatic and,
under normal circumstances, will require about 5
minutes to calculate a navigation solution.
AutoLocateTM,unlikesearchthesky,doesnotrequire
thattheGPS35/36continuetooperateafterafixhas
beenobtained.
8

SECTION 3
HARDWARE INTERFACE
3.1 MECHANICAL DIMENSIONS
TheGPS35isacompleteGPSreceiverincludingantenna
in a uniquely styled waterproof package.
3.1.1 GPS 35 Dimensions (General Tolerance ±0.50 mm)
9

10
3.1.2 GPS 36 Dimensions (General Tolerance ±0.50 mm)

GPS 35 ONLY
11
3.2 MOUNTING CONFIGURATIONS AND
OPTIONS
The following mounting options are available for the GPS
35. Mounting is user configurable.
3.2.1 Magnetic Mount
The magnetic mount provides a firm, removable mounting
attachment to any ferrous metal surface.

12
GPS 35 ONLY
3.2.2 Trunk Lip Mount
Thetrunklipmountprovidesasemi-permanentattachment
to the trunk lip of most automobiles.

GPS 35 ONLY
13
3.2.3 Suction Cup Mount
The suction cup bracket provides a removable mounting
surface attached to the inside of a vehicle's windshield.

GPS 35 ONLY
14
3.2.4 Flange Mount
The flange mount allows for a permanent installation on a
flat surface. This mounting configuration is ideal in
applicationsinwhichthefarsideofthemountingsurfaceis
inaccessible.

15
3.3 CONNECTION WIRING DESCRIPTION
The GPS 35/36 features a stripped and pre-tinned cable
assemblyforthegreatestconnectionflexibility. Thefollowing
isafunctionaldescriptionofeachwireinthecableassembly.
Red: VIN - Unregulated 10 - 30VDC 200 mA
(maximum). Typical operating current is
150 mA.
Black: GND - Power and Signal Ground
White: TXD1 - First Serial Asynchronous Output.
RS-232compatibleelectricalspecification.
This output normally provides serial data
which is formatted per “NMEA 0183,
Version 2.0” . Switchable to 1200, 2400,
4800and9600BAUD. Thisoutputfunctions
in parallel with the NMEA output.
Blue: RXD1 - First Serial Asynchronous input.
RS-232 compatible with maximum input
voltage range-25<V <25. This input may
be used to receive serial initialization/
configuration data, as specified in Section
4.1.
Purple: TXD2 - Second Serial Asynchronous
Output. Electrically identical to TXD1.
Green: RXD2-SecondSerialAsynchronousInput.
Electrically identical to RXD1. This input
may be used to receive serial differential
GPS data formatted per “RTCM
RecommendedStandardsForDifferential
Navstar GPS Service, Version 2.0” (see
Section 4 for more details).
Gray: NMEA-NMEA0183, Version 1.5 electrical
specification compatible serial output.
This output is also CMOS compatible with