Compass issues

[bc214]

Hey guys.

I have been working on my navigation as part of my AOW series (SSI), and have run into some trouble. I purchased a slate/compass combo from trident through my LDS and have become frustrated with it.

On various local limited vis dives I have used it without much difficulty, but also without much expectation of accuracy. Generally, get out to the channel, cruise in one direction for 20 mins, reverse.

In my quarry dives for nav the other day, I could not maintain a heading very well and got very frustrated. It seemed like my compass was forcing me off course even though the heading remained true in the device. Surface later to find I did in fact "pull" sometimes by 10-15 degrees.

I was especially frustrated because I am pretty decent with land nav and moderately handy with a compass.

So today I go outside with my compass and shoot an azimuth and then obstruct my forward view. Following only the compass and IM OFF AGAIN!!! I went back inside and grabbed my lensatic and do the same thing. Spot on with the land compass. Repeat this cycle a few times and I am satisfied that it is either my compass or something that I'm clearly ping wrong with my dive compass.

Inside I inspect the dive compass. I found that, and before I say this I know already that it must be level, that a change of the compass in any direction scrambles the card to the point of being off by up to 15 degrees. Tip it just the tiniest bit forward and north slowly rotates away by an unacceptable amount. Also, the card is slow to respond, which gives me a great chance to mess things up.

I went down to my LDS and looked at some other devices and wasn't super satisfied with any.

Again, I know that the compass must be level, but are there models on the market that are more "forgiving" than this thing?

I have my AOW ocean dives up in RI coming up in a couple weeks, and I would like to try to replace this thing with something a little better and get some practice in first.

Here is a picture of the compass I have, and I'd really love some advice and or recommendations on a fast, forgiving compass.

Thanks,
BC

Sent from my iPhone using Tapatalk

 

[flots am]

Hey guys.

I have been working on my navigation as part of my AOW series (SSI), and have run into some trouble. I purchased a slate/compass combo from trident through my LDS and have become frustrated with it.

On various local limited vis dives I have used it without much difficulty, but also without much expectation of accuracy. Generally, get out to the channel, cruise in one direction for 20 mins, reverse.

Compasses aren't actually all that reliable for short distances. The earth's magnetic field is very weak and it doesn't take much to put your compass off by a significant amount. If you swim by an old car or magnetic deposits or a steel ship, it's pretty much useless.

Also, mechanical compasses are affected by position. If it's not horizontal the needle will jam against the housing.

While it's handy to have and frequently works, it's not something I'd want to use as my only navigation method. Generally I prefer navigating by landmarks (natural navigation).

flots.

 

[AfterDark]

I've never done this but it looks good on paper. Get 2 line levels. These are small one bubble levels masons use to hang on a string to give themselves a level reference. Attach them to that slate 90degs from each other so that pitch or yaw you'll see one of them change. Use them to get a feel for keeping the compass level. Sounds good huh? Finding a way to keep them on while diving would be ideal.

There are no large amounts of iron in RI and a compass is basic gear especially at night when even at the surface direction is tough to determine.

You'll want to be able to use a compass to enjoy diving here in RI. I have used my compass to find my way back to a steel hull ship in NC but you need to watch it to know when it starts moving off the earth magnetic field and onto the ship. Contact me when you get certified we'll do some diving when you're in RI.

 

[RJP]

Trident stuff is, in general, crap. As you're seeing, you don't get enough play on tilting it without screwing it up. Also, however, could be an issue with how you're holding it. Holding a slate-mounted compass by the near end of the slate other than perfectly aligned with your midline and direction of swim will multiply any error you're encountering.

How are you holding it? The best way is cupping the compass itself in BOTH hands out in front of you; this will essentially force you to keep the compass aligned with your body... unless one of your arms is longer than the other. Can you pop the compass out of the slate and try it that way?

My students have good experiences with Suunto SK7 or the Oceanic SWIV compasses - both of these are very forgiving in terms of tilting without getting hung. I use an Oceanic personally; the SWIV's predecessor.

Where in NJ are you located? You're welcome to borrow one from me to try out if you like.

 

[tbone1004]

build one of these, piece of plexiglass from home depot, sand it down so you can write on it. Drill a hole in one corner, and zip tie a bolt snap to it. drill two small holes at the top and put a small piece of bungee on the top to hold a pencil. Superglue a $10 wally world compass to the bottom left corner and voila, cheap very easy to use compass, much better than the floating crap compasses that are barely good enough for cardinal ish directions. I have used the slate in this picture to do a 500yd blue water kick *40ft depth quarry with 15ft of vis and was diving at 10ft depth the whole way* was accurate within 5ft by the time I got to the other end, hit the buoy I was aiming for. It will deviate somewhat when you are close to heavy metallic objects, but you have to be decently close when you're underwater.

 

[lemke]

Look at the different compasses out there... some are very flat, some are thicker. The thicker ones allow a little more angle (to horizontal) and are a little more forgiving.
Check these out from DGE... https://www.divegearexpress.com/tools/compass.shtml

 

[AfterDark]

If you can find one of these in good shape on Ebay, buy it. It is probably the best and most forgiving compass ever made. Someone at Scubapro that probably didn't know crap about diving or compasses decided to stop making them. I use one mounted on a console. In 44 years of diving I'm on my second one, they last too! It is a Scubapro LS-1 compass.

 

[jimbeeler]

Ahem.... Well.... I have a very good <not cheap> compass. I had no end of problems with it on my Nav Adventure dives as well as my Nav specialty... several months ago when in Bonaire I tried to use it to return to the shore. I was pretty sure of the direction but not absolutely positive (navigating on Bonaire is not hard). The damn compass wanted me to go a direction obviously incorrect.

Then a month or so later a friend borrowed it for a student in his Nav class and he brought it back to me and said it doesn't work. Sure enough it was pointing the wrong direction... What the heck... Compasses are not that complicated...

Long story short, I had it on a retractor with a metal cable and a metal ring holding it to the retractor. That was enough to make it read incorrectly. I removed the ring and replaced it with another retractor and a zip tie and presto!

Bottom line is make very sure you have NO metal anywhere around the compass.

Jim

 

[spectrum]

No doubt all compasses are not created equal. A better compass may improve your results. In the end it needs to point north and do so freely. Keeping metal away as about all you can do to help the former. As for the latter be sure to hold it level. The way I make sure I'll be on the mark is with a little wrist rotation to challenge it to hold north. If the card moves with me then it's not free. If it holds north while the body moves then it's doing the best it can.

With a good instrument held well what is the best you can expect? In still water you should be able to hold a pretty tight heading but how often is that the case? The OP mentioned being out in the channel,, that usually means some sort of current, perhaps even tidal. It is easy to swim dead ahead forward but be swept diagonally by a current. Also if you are towing a flag the breeze may cause the towline to skew your course.

If you have visibility to some forward landmarks practice diving in leapfrog mode. Look down the heading for a landmark and swim to it then sight ahead and repeat. After a while you will do this subconsciously. In blue water or on a sandy or silty barren bottom this is much harder. With very limited visibility it ceases to be an option.

Beware of distractions especially in good visibility. That jaunt off of the course to check something out has broken that line you sighted. You can take you best shot at getting back on course but unless you deviated at a landmark you are now compounding estimations.

If you have nothing to work with try to find at least 1 visible landmark and hover. Observe if you are under the influence of any currents and take your best guess in biasing your heading to counteract the side drift.

Practice and sometimes humility will be your friends. Sometimes conditions and deviations will make you happy that you reached shore and didn't swim out to sea. In the end this is usually about fun. If nobody gets hurt, all of the gear comes back and you learn something it will have been a good dive.

Pete

 

[Doc]

....Bottom line is make very sure you have NO metal anywhere around the compass....

Oh, now I remember that metal plate in my head.

I always wondered why I tipped to the port side. Just thought of it as un-ditchable weight.

Mess up my compass, eh?