Orolia GSG-5 Series, User Manual With Scpi Manual, Page: 134 / 392

4.7 Creating a One-Line Trajectory
As the GSG unit uses the heading and speed information of the RMC sentences, only one
NMEA sentence is actually required to describe a simple, continuous movement.
For example, the following one-line trajectory specifies a continuous north-bound tra-
jectory (as the
heading field is set to 0.0 degrees) at a speed of 77 knots:
$GPRMC,111150,A,6000.000,N,0100.000,E,77.000,0.0,140715,0.9,W,A*03
RMC Recommended Minimum Sentence C
111150 Fix taken at 11:11:50 UTC
A Status [A = Active, V = Void]
6000.0000,N Latitude: 60 deg 00.000' N
0100.0000,E Longitude: 01 deg 00.000' E
77.000 Speed over ground: 77 knots
0.0 Heading: 0.0 degrees true
140715 Date: 14-July-2015
0.9,W Magnetic Variation: 0.9 deg West
A Positioning system mode indicator: [A = Autonomous]
*03 Checksum data, always begins with *
One-line trajectories like this can be easily be made by manually creating the desired
NMEA files: The example above can be taken as a baseline, then edit speed and/or head-
ing fields as required.
To allow for testing the sentence's validity, the last 2 digits contain a checksum of the data
(XOR of all bytes between $ and * symbols) – this checksum must be correct and can be cal-
culated with e.g., this online tool:
www.hhhh.org/wiml/proj/nmeaxor.html
.
Note that the NMEA messages, including the checksums, are case sensitive and should be
given in UPPERCASE even if the GSG unit (firmware version 3.00 and above) accepts
messages in lower case.
To find out more about NMEA , and purchase a copy of the NMEA 0183 Standard, visit
www.nmea.org
.
To learn more about trajectories, see: "Trajectories" on page 43 .
4.8 Leap Second Configuration
A leap second can occur on two dates, December 31 or June 30. It is announced approx. 6
months in advance. The GPS almanac changes to ‘announce’ the leap second, and GPS
118 User Manual GSG-5/6 Series Rev. 27
4.7 Creating a One-Line Trajectory