CONTINUOUSWAVE

Just recently, Lowrance announced a new heading sensor which they are calling the PRECISION-9 compass. The PRECISION-9 will provide heading and rate-of-turn data via NMEA-2000 parameters. The PRECISION-9 should be available now (March 2016) and has a suggested retail price of $645.


According to Lowrance, the PRECISION-9 provides "a sophisticated solid-state sensor array measuring motion on nine separate axes." Lowrance also says this device avoids the "common limitations of conventional fluxgate electronic compasses." After calibration the heading accuracy of the compass is specified to be ±2 degrees, with a pitch and roll range of ±45 degrees.

The PRECISION-9 is rated as IPX7 waterproof (immersion up to 1-meter for 30-minutes) and is suited for mountings exposed to weather. The mounting bracket can used to fasten to a bulkhead or to a mast. A single NMEA-2000 extension cable is all that is required to provide power to and receive data from the device.

In addition to heading and rate-of-turn, the PRECISION-9 will also supply roll and pitch data via NMEA-2000.

There is also a Simrad version of this product, also called a PRECISION-9. On the Simrad product page, a reference is made to the device using Microelectromechanical systems or MEMS technology.

The actual compass device is separate from the mounting bracket. The orientation of the compass device in the mounting bracket can be rotated so that the compass becomes aligned to the vessel centerline and thus gives the vessel heading.

Calibration of the compass for the effects of any local magnetic fields is achieved by initiating a compass calibration procedure. The procedure can be initiated by an attached multi-function display on the NMEA-2000 network having the necessary specialized software tool, or initiated automatically within a certain period following power-on by driving the boat in three consecutive revolutions of a circular course with a rate of turn of 2° to 3° per second. Minor offsets of the compass's mechanical orientation with respect to vessel centerline can also be entered in the calibration process if the multi-function display method is used.

The NMEA-2000 data output contains PGN 127250-Vessel Heading, PGN 127251-Rate of Turn, PGN 127257-Attitude, and PGN 130824 (apparently a proprietary datagram). For more information on these parameter groups, see my article on NMEA-2000 parameter groups. The data rates from the PRECISION-9 are listed as follows:

Magnetic heading = 20-Hz
Rate of turn = 20-Hz
Pitch/Roll = 10-Hz
Heave = 10-Hz

Although the marketing literature has not mentioned the heave data, it appears in the product installation instructions in the specifications listing. Information on heave can be used with certain sophisticated SONAR devices to remove the effect of the vessel's up and down movement relative to the sea bottom in waves. At this moment there appears to be some uncertainty about the heave data function from the PRECISION-9 compass, and it may not be present in the first release of production.

Since I am not a NMEA 2000 wiz, I assume that if you want to add this sensor, you need an existing unused [network backbone port]. Correct?

Yes. The PRECISION-9 connects to the network just like all network devices--by a single cable from the device to the network backbone. Of course, the usual network requirement that no drop cable be longer than 18-feet must be observed.

NAVICO mentions the "single cable" connection as a feature in all their literature about the PRECISION-9. I suspect that the inference is that you don't have to run a separate power circuit to the device, or to interface it with some special multi-conductor cable. It is just a NMEA-2000 device and is network-powered. This gives the PRECISION-9 some flexibility in choice of location to mount it.

Heck, if it uses microelectromechanical systems (MEMS), it should not need much power. And it doesn't. The NMEA-2000 load equivalent number is 1-LEN (or 0.05-Ampere or less), the least amount of power that can be drawn by a NMEA-2000 device.

Also, the PRECISION-9 has no GNSS receiver. It does not need to be mounted with a view of the sky. The PRECISION-9 can installed low in the boat on the keel centerline where it will probably work the best.

Since the PRECISION-9 communicates using NMEA-2000, it should be noted that in legacy NMEA-2000 there was no parameter group for HEAVE. This may explain why there is some uncertainty about support for HEAVE in the PRECISION-9 data output. In a c.2014 presentation, NMEA said it there was a NMEA-2000 "additional message" for HEAVE that "was to be published." This suggests that perhaps only the most recent devices are able to support a NMEA-2000 PGN for HEAVE data, assuming that NMEA has published that additional message description.

(Heave is the up-and-down motion of a vessel in the vertical plane.)

I searched for recent articles on the PRECISION-9 heading sensor, but the results were mostly magazine or website notices of its introduction. No user experiences were found. Has anyone installed a Simrad or Lowrance PRECISION-9 heading sensor?