Correct mounting procedure for gps and magnetic compass.

[jurgenscraft]

Good evening, can any body advise me as to the correct distance I should keep between my magnetic compass and the gps and other electronic systems,on board my boat,or do these elecromagnetic fields generated by these electronic instruments have no effect on the magnetic compass, all the metal fittings within the vicinity are of a high grade non magnetic stainless steel or aluminium so they are not a issue.I have seen some installations that have the compass mounted right next to electronic equipment, I think I need to ask you guys on this forum before I start to drill big holes for the bulkhead fitting compass and then find that the headings are not accurate.Kind Regards William Wright.

 

[AndyL]

Re: Correct mounting procedure for gps and magnetic compass.

Before you drill any holes offer the compass up to where you would like it placed then switch on all likely to be running electronics and see if the compass shows any deviation.ie note the heading with electonics on, then note the heading with electronics/nav lights etc off. The difference is the deviation caused by the magnetic fields of the instruments. If this is significant then re-site the compass and try again. Finally drill the hole or move the electronics so they don't cause significant errors.

 

[18rabbit]

Re: Correct mounting procedure for gps and magnetic compass.

Andy has some good advice on how to detect for compass deviation.<br /><br />Back to your original question, everything has an effect on a compass. Some things more so than others. Electronics is high on the list of stuff that will cause erroneous compass readings. The manuals for marine electronics usually indicates the distance from the compass the electronics should be. In general, 3-ft/1-meter seems to be pretty popular. In reality, very few boats have an unused space that is a circle 2-meters in diameter that you can mount your compass in the center of.<br /><br />That’s why Andy has good advice. One of the most overlooked, and major offenders of compass deviation is windshield wiper motors. You should check for deviation with those critters running as they tend to be in close proximity of a dash-mounted compass.<br /> <br /><br />Note: Compass deviation is caused by local influences on the compass. They are often temporary, like when you engage your windshield wipers. But they can also be permanent, like having metallic objects mounted near the compass. Compass variation is different. It is the difference between your compass' natural Northerly reading (magnetic north) and actual, true north. Its primary cause is the variance in the earth’s magnetic field. Compass variation will change relative to your geographic location, compass deviation will not.

 

[DangerDan]

Re: Correct mounting procedure for gps and magnetic compass.

I had to deal with this earlier this spring when I installed my GPS. As the other posts indicate, Do not set the screws until you can be sure of any deviation. My compass had settings to correct deviation from electronics, After I got everything set I ran the boat for a few trips to assure my compass was accurate then I set the screws in place.

 

[jurgenscraft]

Re: Correct mounting procedure for gps and magnetic compass.

Thank you for the speedy replies and thank you for the information regarding my question I think I will take the boat out and check both systems and see what happens, check the deviation between the two systems ie. magnetic and gps campasses and set up after these tests.

 

[Boatist]

Re: Correct mounting procedure for gps and magnetic compass.

On my boat the fish finder 6 inches away has no affect on compass. Loran C 6 inches away has no affect. GPS 1 foot away has no affect. VHF Radio has no affect. 6 inch External speaker for the VHF Radio start to affect compass at about 3 and 1/2 feet. Winsheild wiper motor when on has 10 degree affect but it and the compass came installed on the boat when new. So I turn the wiper off when I need a compass heading.<br /><br />At a dock or on the trailer hook your gear to the power and turn it on move it close to the compass and see if it moves. When mounting use Stainless steel screws or at least some non magnetic screws.