MD71EMC Electromagnetic Compass System

An Electromagnetic Compass (EMC) System which detects the Earth’s magnetic field and transmits the ship’s Heading over a digital NMEA 0183 connection to remote Heading Repeaters.

SKU: F071101 Categories: ,

The MD71EMC Electromagnetic Compass System

The Marine Data Systems MD71EMC is an Electromagnetic Compass (EMC) System which detects the Earth’s magnetic field directly. It then transmits the ship’s Heading over a NMEA 0183 digital connection to one or more Heading Repeaters installed at any convenient location on a vessel. The EMC has no moving parts – unlike a TMC (Transmitting Magnetic Compass) which detects the moving compass card of a ship’s compass in its binnacle.

The MD71EMC uses the latest technology to accurately process and convert the ship’s magnetic compass heading to NMEA 0183 heading data with unparalleled accuracy at speeds of up to 70 knots and rates of turn up to 20° per second. The system has been developed with improved magnetic correction facilities to reduce deviation effects caused by the magnetic influence of the craft. The compactness of the complete system makes it particularly appropriate where the size of the craft makes it physically impossible or financially imprudent to install a gyro.

The MD71EMC Transmitting Magnetic Compass System fromMarine Data: Flexible in application, easy to install and simple to maintain.

The use of a Magnetic to Digital system

Increasingly, Maritime Authorities are accepting the use of Transmitting Heading Device (THD) Systems on board vessels. Marine Data offers two types of THD system:

  1. A system which senses the angular position of a ship’s magnetic compass card; this is known as a Transmitting Magnetic Compass System (TMC). This type of system provides a digital heading from an existing host magnetic compass installation in its binnacle; it detects the position of the moving compass card
  2. A system which directly senses the Earth’s magnetic field; this is known as an Electromagnetic Compass System (EMC). This type of system provides a digital heading directly from the Earth’s magnetic field; it does not require a host magnetic compass; it has no moving parts

Special Features

  • Automatic calibration with host ship’s magnetic compass by turning the ship through 390°
  • The MD71EMC has no moving parts; also known as a solid state compass
  • 2x power supply inputs; 2x NMEA 0183 data channels output
  • Bright OLED display provides good clarity with high contrast and wide viewing angles


  • Provides a digital NMEA heading output to drive a Heading Repeater (or other devices) at a convenient location
  • A solution for when size of the craft makes it physically impossible or financially imprudent to install a gyro

Parts included in this EMC system

Related Products

**The MD71THD Control and Display Unit is capable of displaying the heading in numeric form as a basic heading repeater (compass repeater). However, we always recommend using a dedicated Marine Data Heading Repeater suitable for the precise purpose to which it will be used (a repeater for steering the vessel; a repeater taking bearings; a repeater to be mounted on the bridge wing, etc. See the full range here)


  • Weights & Dims: MD71THD: H 96; W 96; D 35 (mm); 0.50 kg    MD97CSP: L 146; W 64; D 41 (mm); 0.35 kg    MD53A/B:  H 166; W 142; Ø 123 (mm); 1.00 kg    Excludes cables & connectors
  • Mounting: MD71THD: Panel mount; Trunnion mount optional    MD53A/B: Integral Trunnion Bracket
  • Connections: MD71THD: 15-way D-type plug; 9-way D-type socket;    MD53A/B: Buccaneer™ type male    MD97CSP: Buccaneer™ type female; 1x Gland
  • Finish: RAL7040 Window Grey, semi-gloss


  • Power Supply: 24 V dc; 6 W
  • Data Output: 2x NMEA 0183 Data Channels
  • Data sentences: HDT, HDG and HDM


  • Performance: ± 1° (static) accuracy
  • Display: 7” (128 x 64 pixels); OLED – Yellow
  • Accuracy: <= 0.5° after ADC (depending on sensor)
  • Alarms: Audible sounder


  • IP Rating: MD71THD: IP54    MD97CSP: IP65    MD53A/B: IP65
  • Operating Temp: -15° C to +55° C
  • Storage Temp: -25° C to +70° C
  • RoHS: Compliant
  • Compass: Safe Distance: (MD71THD & MD97CSP): 50 cm


  • Complies with: IEC 60945; IEC 61162-1


  • Supplied on a trunnion mounting bracket ready for installation

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