Compass - any one use it yet?

[Scared Silly]

So our analog compasses went tits up during our last trip. Getting replacement modules turned out to be a bit of a PITA not mention $$$. There are better and cheaper analog alternatives. Now Shearwater releases the Petrel with a digital compass. For the number of times I really need a compass underwater I am willing to give it a try - but that would mean selling our current petrels. My local shop did not have a Petrel2 in stock and the tech who went to DEMA did not try the compass.

Some digital compasses response pretty quickly others not fast. Accuracy is also an issue. As such, I am curious to get some feed back from those who have been early adopters and used the compass.

 

[tursiops]

Just playing with it, I'm really impressed. Very fast response, certainly matches the accuracy of my analog compass, relatively easy to use, and it will be VERY easy to see!

Won't be able to get wet with it until next week.

 

[Scared Silly]

Thanks, please post up when ya get it wet.

 

[James R]

I used it on a few dives this weekend, doing checkouts for one student, so I was able to show her a heading I wanted her to go on with it, then let her set her regular compass. It worked out really well.

I will say that it seems very sensitive, meaning it changes heading display quite quickly rather than lagging behind like some others I have seen & used. I also like that it displays the compass until you tell it not to, rather than displaying it for a few seconds then changing back to the default screen.

I still have and will continue to use my bungee-mounted compass primarily, though.

 

[undrwater]

I'm curious how your analog compass failed.

 

[Rich Keller]

Though I do not use it much I would rather not have something that depends on batteries.

 

[Scared Silly]

I'm curious how your analog compass failed.

The seals on the modules failed so they started leaking and got air bubbles in them. The air bubble was not so much the issue but more the leaking was a mess as the fluid is not water but a very light mineral oil.

 

[James R]

I have had a couple regular compasses fail: one got stuck somehow and wouldnt turn at at all, the other got bubbles in it and would turn, but very slowly and not all the time.

 

[triode12]

Does one have to calibrate the compass on the Petrel before each dive?

 

[tursiops]

Probably not, but it only takes a minute to do.
There are two errors: one is inherent in an electronic compass, and that is what the calibration routine takes care of easy. I do this calibration when I arrive at a dive location, and check it every few days.
The other error is more subtle...at best, the compass points toward magnetic north, which is not the same as true north; the difference is called magnetic deviation. This error is affected by location, by time (the magnetic poles move around), and by propinquity of ferromagnetic objects. At my location, a compass reads about 10 deg in error (West of true North). If I go to Bonaire, it is almost the same, but in Mexico ii reads 9 deg East of true North! At my location, it changes only 1 deg per year, but 5 deg per year in many other locations. See World Magnetic Model - Home Page for a discussion of this, with maps and calculators.
If you are using your compass to take a heading on a mooring ball before swimming to it underwater, the magnetic deviation is irrelevant...you are doing relative navigation. If you look on a map and see you want to swim due East, you need to know the deviation...it might be small, but it might be 30 deg in high latitudes. Sydney reads about 12 deg East of true North.