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190-00228-08 GPS 16x Technical Specifications Rev. B
Page 15
4.2.2 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 one-pulse-per-
second 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). This
document is for 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
4.2.3 Global Positioning System Almanac Data (ALM)
Almanac sentences are not normally transmitted. Almanac transmission can be initiated by sending the GPS sensor a
$PGRMO,GPALM,1 command. Upon receipt of this command, the GPS sensor will transmit available almanac
information on GPALM sentences. During the transmission of almanac sentences, other NMEA 0183 data output
will be suspended temporarily.
$GPALM,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,<10>,<11>,<12>,<13>,<14>,<15>*hh<CR><LF>
<field information> can be found in
section 4.1.1 Almanac Information (ALM).
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
<6> GPS quality indication, 0 = Fix not available, 1 = Non-differential GPS fix available, 2 = Differential GPS
(DGPS) 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> Differential GPS (RTCM SC-104) data age, number of seconds since last valid RTCM transmission (null if
not an RTCM DGPS fix)
<12> Differential Reference Station ID, 0000 to 1023 (leading zeros will be transmitted, null if not an RTCM
DGPS fix)