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Marine - Shipboard Dead Reckoning Equipment (DRE)


Dead Reckoning is the form of navigation where by the ship’s position can be determined by keeping a record of the distance traveled on each of the courses traveled. Rather than performing these calculations individually the dead reckoning system gives a continuous indication of the ship’s position and will graphically plot the ship’s course.

Dead Reckoning Equipment Types:

Dead Reckoning Analyzer (DRA)

The DRA receives the ship’s distance input from the ship’s speed log, and ship’s course input from the ship’s gyrocompass. These two inputs are combined to determine and indicate the total distance and also the overall distance in north – south and east – west directions traveled by the ship from any given starting point.

Dead Reckoning Indicator (DRI)

The DRI is contained in the tracking mechanism of the dead reckoning tracer (DRT). It consists of a dial unit and assembly that include the latitude motor and associated dials, and the longitude motor and its associated dials and the latitude corrector mechanism. The north – south and east – west output of the DRA drives the latitude and longitude motors and their associated gearing and dials.

Dead Reckoning Tracer (DRT)

The DRT consists of (1) a tracking mechanism; (2) a chart board that includes the pencil carrier assembly; and (3) an auxiliary plotting board. The auxiliary plotting board is included with the DRT for plotting ranges and bearings of contacts that are being tracked and for plotting own ship’s course. The DRT is housed in a metal case designed for horizontal mounting on a table or cabinet and is typically located in the ship’s combat information center (CIC).

Dead Reckoning Analyzer Indicator (DRAI)

The DRAI provides essentially the same information as the DRA, however the outputs are derived electrically instead of mechanically, and the DRAI can be used independently of a plotting table. When used independently it provides a counter indication of the ship’s position in terms of latitude and longitude, total distance traveled, total distance E-W total distance N-S and ship’s heading and speed.

Navigation Computer Plotting Systems (NC2) & (PT512/S)

The Anti Submarine Warfare (ASW) plotting systems NC2 and PT512/S are used in the ship’s Combat Information Center (CIC) or similar shipboard areas for dead reckoning plotting of ship’s position and moving or stationary underwater, surface, or airborne targets. The systems are used extensively for ASW operations and related tactical situations, as well as an aid to navigation.

shipboard dead reckoning analyzer

Mk 6 mod 1 DRA
Mk 6 mod 4 DRT
Mk 9 mod 2 DRAI
Mk 9 mod 4 DRAI
Mk NC2 mod 0
Mk NC2 mod 1 & 1A
Mk NC2 mod 2 &2A

Equipment Manufactured By:
Arma Corporation
Litton Systems
Gap Instrument Co.
Martin Marietta
Reflectone (Otis Elevator)
Hartman Huyck
Hartman Systems Co.
Sperry Marine
Marsland Eng Co.