Manual

June 2004 Isis® Sonar User's Manual, Volume 2
54
RMC // Recommended Sentence C with date, time, latitude,
longitude and heading
GGA // Time and position (in latitude and longitude)
GLL // Latitude and longitude
VTG // Course and speed made good
ZDA // Time and date
Each of the first four of these sentences can be disregarded by adding to
the navigation template, NOGGA, NORMC, NOGLL, and / or NOVTG
respectively.
In addition, Isis now supports these strings:
VTG // Heading, Speed
ZDA // Date, Time
HDM // Gyro
SHR // Position, Date, Time
D.4.1.3 Real-Time Kinematic
Certain GPS receivers can use a mode known as Real-Time Kinematic, or
RTK for short. This RTK mode can measure the antenna height (Height
above Geoid) very accurately.
There are at least two methods of transmitting this data to a recording
instrument such as Isis. The first is in a modified version of the NMEA0183
GGA string; the second is a special string used by Trimble RTK receivers
known as a GGK string.
Isis stores the altitude information from these strings (if they are present) as
Ocean Tide. The priority assigned to the strings is that if a normal GGA
string and a GGK string co-exist, then the altitude information in the GGK
string will be stored in the XTF file.
The Trimble GGK string takes this form:
$PTNL,GGK,023157.00,032800,4740.019328,N,12223.743061,W,1,06,
2.6,EHT53.271,M*55
where the value EHT53.271 will be saved into OceanTide field in the XTF
file. When GGK is not present, the Altitude above Geoid from the GGA
message is stored as OceanTide.
Appendix D: Serial Interfaces