Garmin Garmis GPS Smart Antenna GP35-LVC - Manual (Page 23)

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4.2.2 Transmitted Time
The GPS 35LP receivers output UTC (Coordinated 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 GPS 35LP 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)” (for sale by the Superintendent of Documents, U.S. Government Printing Office,
Washington, DC, 20402, USA).
When a positive leap second is required, the second is inserted beginning at 23h 59m 60s of the last day
of a month and ending at 0h 0m 0s of the first day of the following month. The minute containing the
leap second is 61 seconds long. The GPS 35LP would have transmitted this information for the leap
second added December 31, 1989 as follows:
Date Time
311289 235959
311289 235960
010190 000000
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 35LP will not
transmit the time of day 23h 59m 59s for the day from which the leap second is removed.
4.2.3 Global Positioning System Almanac Data (ALM)
<field information> can be found in section 4.1.1.
$GPALM,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,<10>,<11>,<12>,<13>,<14>,<15>*hh<CR><LF>
Almanac sentences are not normally transmitted. Almanac transmission can be initiated by sending the
sensor board a $PGRMO,GPALM,1 command. Upon receipt of this command the sensor board will
transmit available almanac information on GPALM sentences. During the transmission of almanac
sentences other NMEA data output will be temporarily suspended.
<field information> can be found in section 4.1.1.
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<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