Heading Sensor

M

mawyatt

New Member
Dec 13, 2007
1,001
Clearwater, Fl
Boat Info
2008 Sundancer 38DA
Engines
8.1L Mercruisers
We finally got our new boat and took our first outing (not with capt) this past Sunday. We ran into some dense sea fog and ideled our way back. The RM Chartplotter (E120) was showing our heading bouncing all over, so I just used the compass and tried to use the E120 display to stay in the narrow intercoastal channel.

I've been told on here (thanks) you need a heading sensor to get good headings at low speeds. We will add RM radar soon and want the radar display over the chartplotter which requires the heading sensor. What exactly as a minimum do you need to interface with the E120 to get the heading, are there other brands that work are better or cost less? I did find a RM Fluxgate M81190 on e-bay...will this work?

I have a lot to learn,

Thanks,

Mike
 
I'm not sure how the E120 is getting any "heading" data if you are only using a GPS. Showing COG on the E120 should give you a pretty steady reading, but will only be accurate as long as the boat is moving. COG should be much more steady than heading anyway.
 
back in 2001, on my '98 330DA, when I installed my first RL70CRC with overlay, RayMarine had just come out with overlay but didn't have their own product to provide a fast enough heading sensor. At their advise, I replaced the onboard compass with a KVH unit for about $250. Jim (BOE) may have these units. It was an easy install and fit right in/over the existing compass hole. I did have to drill three small screw holes to fasten it and run the NMEA cable from the KVH to the RL70. Worked great....and the added bonus was that with the electronic compass, it was "damped" so it didn't bounce all over the place in seas.
 
If you ck the raymarine web site you will see the smart heading sensor you need and they are available on ebay. Installation is simple plug and play,as long as no metal around and in center line. Mine on my 320 is mounted below my helm seat toewards center line. It also includes pitch, roll, and yaw. If you read the spec's on raymarine web without the sensor your e120 updates 10x a minute with it's 100x or something like that. Any way it's a lot faster with the smart heading sensor and I think it's a must have especically in the situation you desrcibed.
 
The Raymarine fluxgate compass (part of the smart heading sensor) is a piece of poop. I keep thinking of replacing it with a high quality one like the KVH but never get around to it. The Raymarine one has a dangling thingy inside that if hits or bangs the side of the housing, knocks it out of calibration. Not sure I want a fluxgate compass with moving parts...

Also, I think this is the second thread were someone thinks the GPS, while moving, will send out the heading over the NMEA network. The GPS sends out the COG value on the NMEA network and NOT the heading value... if a device is looking for the heading value, it may well IGNORE the COG value as that is NOT what it is looking for. I know my Airmar weather station needs the heading value to work right and does not recognize COG for true windspeed calculations (although it does pull the SOG for those calculations)... you can trick it to accept COG via a multiplexer and rewrite the data but who wants to go there. GET A HEADING SENSOR!!!!
 
So how does it know which way the pointy end of the boat is pointing? If you say it'll automatically fall back and use the COG data from the GPS, shame on Raymarine.
 
When you are underway the pointy end is typically going in the direction of your gps movement. If you are drifting or anchored then this isn't the case. You know all this stuff! Raymarine and Garmin do not require a heading sensor for overlay. Furuno does. I say shame on Furuno since more money is required to make an advertised function work. If you want things to line up perfectly then you should get a heading sensor. Remember, all these gizmos are only an aid to navigation, the user has to know what they are looking at and have real expectations of the data. I have a heading sensor on one of my boats and use radar overlay with a Ray E120, and I don't have a heading sensor on the other and use radar overlay with a Garmin 5212. I find them both equally accurate while underway.
 
Well.. I'll disagree. The accuracy of COG decreases the slower you go. If you are going 20 knots, sure... But when you get down below 10 knots, there is going to be several degrees of error to the point you stop where the error is infinite. The calculations are based on somethng that is within 30 feet or so when the readings are taken for the calculations and if the location error is significant relative to the time between readings, you can have several degrees of error. I find having having more than a few degrees of error annoying and pointless on the overlay as things just don't line up... Think about going 8 knots and having waves push you around with no visibility due to a squall line. Just when you need accurate overlay info, you don't have it.

The reason I know this? Because my freekin' fluxgate compass is a piece of poop and my airmar weather station GPS and heading sensor is very sensitive...

MY 2 cents...

Mr. Air Force.
 
This is an excerpt from the Pathfinder series of Radars:

The following criteria must be true for radar/chart overlay to function
correctly:
• Position and heading data are provided so that vessel position and orientation
can be determined.See Heading and Position Data on page 1-9 for​
further details....
.............

AND, on page 1-9.....

Providing Heading Data for Radar/Chart Overlay and MARPA
The performance ofMARPAand Radar/ChartOverlay is dependent on the
quality of your heading sensor. It is important that both the heading sensor and
the radar scanner (bearing alignment) are correctly calibrated. Refer to the
appropriate heading sensor and radar scanner handbooks for calibration
details. The better the accuracy of your heading data, the better the
performance ofMARPAand Radar/ChartOverlay.
Agyro compass provides the best performancein all conditions.Alternatively
you could use a fluxgate compass with rate gyro stabilization.
MARPArequires heading data to be frequently updated (we recommend a
data output rate of greater than 8Hz); heading data must therefore be provided
to the display onNMEA.
In multiple-display systems, headingmust be connected, viaNMEA, to each
display that will be used forMARPA.
We recommend the Pathfinder Smart Heading System (which includes the
Gyro Plus 2 unit).Good results are also obtainedwith a Raymarine autopilot
systemincorporating a 150G or 400G Course Computerwith internal rate
gyro.
Other heading sensors connected onNMEA may provide satisfactory results
in reasonable sea states. However, in unsettled conditions a rate gyro compass
is advisable.
Contact Raymarine Customer Services or your authorized Raymarine dealer
for additional information. For specific configuration details with the
Raymarine course computer refer to Appendix E. If you are using a suitable
third party heading sensor, refer to its documentation for installation and​
calibration details.

I'm not sure about the newer E/C Series stuff....
 
I think Jim is just up there with all the other sissy boaters where you can spit and hit the other side of the bay and "unsettled sea conditions" means the boat wakes are bigger than the waves. Oh... He'll tell you he's traversed the globe and panama canal... yeah... right... He sells trawlers on the river.
 
Sorry Gary, that was me posting on wifey's laptop (airforce). You are right, as the boat slows down the chart and radar layers get less "lined up". Radar overlay is certainly neat but not what you should be using when you actually NEED radar. If I am relying on radar as my eyes I will have a radar window open and not use overlay. It is too easy for targets to get lost or missed when they are combined with all of the details on a chart. When I run at night for example I will have the screen split between chart and radar, and direct most of my attention to the radar. Anyway, the heading sensors are not required but do help.
 
Coulda sworn this thread had 3 pages a minute ago...guess I was too slow.
 
If you guy are going to moderate, then moderate, but stop making stuff dissapear. For those of us who use this site to learn, it makes it very difficult to follow threads when we come back to one and find it or parts of it gone.
 
Sorry Frank, Gary called Bill and all upper bay boaters a sissy, Bill called Gary an ass, I called Gary a sissy since I am an upper bay boater, then Gary did a joke about Four Winns and cactuses and how the prick is on the inside of the Four Winns or something to that affect. I am terribly sorry for removing this, you are right, we should spend much more time to actually edit posts so that the important content can remain, while removing the bad stuff. I guess this could have applied to the heading sensor discussion...maybe we could have said the prick on the cactus is to the west according to the heading sensor or something. I'll be sure to instruct the mods to leave this stuff on the forum so you can learn from it.
 
I think it's essential to know which side the prick is on....but that's just me.
 
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