Compass calibration

[C. Trembanis]

Has anyone used their GPS set for magnetic North, to calibrate
their bulkhead magnetic compass????? Seems to me one could
tweek it more... any opinions welcomed...

 

[wolly bugger]

compass

Hi Chris, I see that you got your compass back together. I'm glad it work out for you.

 

[C. Trembanis]

Compass

Yes thanks Stephan... Worked out very well. Had to destroy
the original bezel, srews rusted...... Now to tweek the calibration...
thanks again

 

[wolly bugger]

compass

Chris, if your screws where all rusted, they must have been metal. My new compass came with plastic hardware to attache it to the bulkhead. Brass or 316 SS will work just as well. You may have know all of that but just in case.

 

[C. Trembanis]

They were original i guess.. I canibalized from the compass you sent.

I was able to adjust the calibration. Now to check it with the GPS
set for magnetic north..... regards chris

 

[Randy Rutledge]

Remember that the GPS must be moving and gives the heading you are actually traveling and the compass gives a heading relative to the point of the boat and Magnetic North hardly ever the same when under sail and motoring in current.

 

[Guy Stevens]

THere is a process

The best place to read the process is in American Practical Navigator, otherwise known as Bowditch.

Here is a link to a free download of it from the US Gov...

http://msi.nga.mil/NGAPortal/MSI.po...NONE?_nfpb=true&_pageLabel=msi_portal_page_62

Select American Practical Navigator in the download box.

Select Chapter 6 as that is the one dealing with compasses.

You want to read all of chapter 6, but the nuts and bolts of adjusting the compass are in section 606.

Better yet is to find a copy of Bowditch from the 60's or 70's as this has the method stated better with more pictures, and without the gyro compass reference... These are the best years of the book for those of us on small boats, as they are more aligned with our technology and space considerations.

You can make a simple azimuth circle with a couple of pieces of cardboard.

Another great, and more in depth reference also free is: https://www1.nga.mil/ProductsServices/NauticalHydrographic/Related Documents/HoMCA.pdf



Have fun!
Guy

 

[footrope]

The best place to read the process is in American Practical Navigator, otherwise known as Bowditch.

Here is a link to a free download of it from the US Gov...

http://msi.nga.mil/NGAPortal/MSI.po...NONE?_nfpb=true&_pageLabel=msi_portal_page_62

Select American Practical Navigator in the download box.

Select Chapter 6 as that is the one dealing with compasses.

You want to read all of chapter 6, but the nuts and bolts of adjusting the compass are in section 606.

Better yet is to find a copy of Bowditch from the 60's or 70's as this has the method stated better with more pictures, and without the gyro compass reference... These are the best years of the book for those of us on small boats, as they are more aligned with our technology and space considerations.

You can make a simple azimuth circle with a couple of pieces of cardboard.

Another great, and more in depth reference also free is: https://www1.nga.mil/ProductsServices/NauticalHydrographic/Related Documents/HoMCA.pdf



Have fun!
Guy

Thanks for the references, Guy. I wish I didn't have to log off and do my taxes right now.

 

[paul culver]

Simplest of all is to make a compass correction card. Motor in 45 degree increments on your compass and note the corresponding GPS magnetic course.

--Paul
E29 "Bear"

 

[C. Trembanis]

compass correction card

Thanks.. I believe this is the way.

Thanks to all the advice from all the rest.....chris

 

[Guy Stevens]

Not really

Using a GPS gives you a lot of other factors that you need to take into account, such as current and leaway, even when the GPS is reading magnetic it is only reading your Magnetic course over ground, not your heading. Your GPS is generally not going to give you an accurate heading to compare to your steering compass.

Also taking out the deviation of a compass using the magnets that are in the compass for compensation, then making up a deviation card, results in a much smaller amount of deviation, and is easier for anyone to actually steer and compute a course.

Guy