Knowledge Base
talker
In the NMEA 0183 Standard, the originator of messages across an NMEA 0183 link.

talker identifier
The first two characters following the "$" (HEX 24) in an NMEA 0183 sentence (address characters 1 and 2).

TD
Time Difference. In Loran-C, the time difference measured from the time of reception of the mater station signal to the time of reception of the slave station signal.

temperature range
the temperatures between which the product will accurately operate.

time difference
(TD) In Loran-C, the time difference measured from the time of reception of the mater station signal to the time of reception of the slave station signal.

track
The intended or desired horizontal direction of travel with respect to the earth. The track expressed in degrees of the compass may differ from the course due to allowances made in the course due to allowances made in the course for such factors as sea and weather conditions in order to resume the desired track.

track made good
A single resultant direction from a point of departure to a point of arrival at any given time.

TRANSIT
Navy Navigation Satellite System. An obsolete satellite navigation system of the United States conceived and developed by the Applied Physics Laboratory of John Hopkins University for the U.S. Navy. It is an all-weather, worldwide, and passive system used primarily for the navigation of surface ships and submarines. Also known by the acronyms NAVSAT or TRANSIT, it consists of a constellation of orbiting satellites, a ground system of tracking station, and any number of user stations (navigators). The user stations are radionavigation devices composed of a receiver, a frequency cycle-counter, and a computer. The minimum constellation for system operation is four satellites (five satellites in orbit provided redundancy). The satellite orbits are controlled by the tracking stations. Satellites broadcast current known positions while orbiting the earth. The NAVSAT system utilizes the Doppler shift of radio signals transmitted from the satellite to measure the relative velocity between the satellite and the navigator. Knowing the satellite orbit precisely, the navigator’s absolute position can be accurately determined from this time rate of change of range to the satellite.

true bearing
Bearing relative to true north; compass bearing corrected for compass error.

true heading
Heading relative to true north.

two-way communication protocol
A protocol established between a talker and a listener in which the listener may also issue requests to the talker when required [compare to One-Way Communication Protocol]. NMEA 2000® is a Two-Way Communication Protocol.

 
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