Is anyone aware of any info as to how to pack a compass to protect it inside a vehicle? I like to keep an inexpensive compass in the truck glove box in case, well just in case the good one is still at home on the dresser. My concern is that prolonged exposure to the truck's magnetic field will change the magnetism of the compass. Have there been any studies done? Does anyone care about compasses anymore? And what about Mary Lou?
These are the kind of questions you get from people who are sitting around waiting for the next job to come in.
Well, I've never had a problem with mine and it stays in the truck unless I'm out working. With the silva compass with the liquid filled version, if you keep it next to your body over time, it will develop a bubble. I have a brunton pocket transit. Never have any problems. I check it a couple of times a year either through sunshots or just observing a static line with GPS vectors and adjusting via convergence angles.
I'd worry more about the declination changes over time than the magnetic pull of the truck messing with the needle.
However, when I find my compass returning different results, I then check the NGS website for declination and find it's changed "some" or I wasn't holding my mouth right when I used the compass.
All in all, I'd say less of a worry than what you may be thinking. The only tests have been my "observations" over the years (20) and sunshots or gps vectors for the gods honest answer.
I've never noticed any problem with storing a compass in a vehicle. On some,you will need to recharge the needle (using the car battery) every now and then to keep it's polarity strong. I think this might be why some drift over time as they no longer react as strongly to the magnetic fields. That's a SWAG though and not scientifically confirmed, at least not by me.
Don't you mean "Mary Ann"?
Definitely over Ginger. No question. High maintenance versus the original version of Daisy Dukes. Oh my.
Deral,
Recharge using the car battery?
Never heard of that.
Jimmy
Willard,
I asked a similar question to an equipment vendor several years ago. I keep two compasses in each one of my work trucks. A sighting compass for instrument backsights, and a silva polaris compass for rough recon work and general direction determination.
I was worried about storing them together in the same compartment or glove box, etc., and the vendor told me that there should not be any issues.
Hopefully that will help.
Jimmy
Not really recharge but just strengthen the polarity of the needle. You touch it to the negative side of the battery and it restores it's polarity.
Did it with compass and with the dip needles, which are basically a compass.
Sorta like touching the top of an iron rod after driven with a magnet.
Deral,
If the needle was in a liquid filled housing, would you just lightly touch the capsule to the post to get the needle close?
That is pretty cool. I've never had to do that with an iron pin. Probably should for future corners.
Thanks for sharing,
Jimmy
Not sure if the liquid ones could be done like this. I doubt it.
On all of mine you can remove the glass and then lift the needle off it's seat to do the polarity whack. Sometimes the seat needs to be worked on also if the needle sticks. A bit of emory cloth or replacement sometimes.
Pretty delicate instruments if treated correctly.
> Willard,
>
> I asked a similar question to an equipment vendor several years ago. I keep two compasses in each one of my work trucks. A sighting compass for instrument backsights, and a silva polaris compass for rough recon work and general direction determination.
>
> I was worried about storing them together in the same compartment or glove box, etc., and the vendor told me that there should not be any issues.
>
> Hopefully that will help.
>
> Jimmy
I've been carrying an older compass around in the truck but always wondered if the accuracy was compromised.
Willard
My animal magnetism seems to ruin them immediately. Similar problems with stud finders.
My Silva and Pocket Transit have been in rigs for years with no problems. The problem starts when I try to follow a straight line and shoot it along the way. Do much better by getting the direction right at one point, project it ahead from that point and then follow the line and not the compass.
jud
I have given most every new recruit a cheap $3 compass to learn something about direction because I give instructions using N,S,E,W half the time.
Have used many different type of compass in the last 50yrs and knowing and setting the correct declination is the most important thing about a compass.
New needles were rare 30yrs ago and probably only found in museums today. I just got a 2in K&E thru Ebay recently and have been thinking how to best regenerate its needle. It works fairly well out in the woods and not so well around any interfering object. Inside a vehicle or in the house it will not settle easily. For some reason all my strong magnets have disappeared so that option is out for the moment.
Deral, How shurefire of a method is the battery post fix?
It has always worked for me. I cannot remember which end of the needle you touch to the negative post but if you get the wrong one then just turn it around and do it again to align the polarity. So check it before you seal the compass back up.
The problem with an old compass is that sometimes the glass will be hard to remove as the seals tend to harden and become brittle. Pry carefully a little at a time around until the glass comes off.