Underwater ball compass



I was watching a video of a homebuilt ROV on YouTube and it had ball type compass placed in front of the camera viewport. http://www.youtube.com/watch?v=1VvX0pxmmNQ&feature=player_detailpage#t=32s

I was wondering:

a) what's the official name of that part? Ball compass?

b) Where do you get them from?

I've seen those types of compasses in cars and on boats before, do you think you could just use one of those or would they break under pressure?



Not sure, maybe just an analogue compass. Seems as though it'd be easy enough to test.

I sail with a lot of old-school sailors and they only go by the analogue instruments - don't trust the digital. Might be useful to have both. Now, to find a cheap source...


I am using a liquid filled compass on my DPV (dive propulsion vehicle), this one:


I am planning to find a smaller one to mount in front of the camera.

A lot of cheap alternatives to test here :) :



I believe they're called 'globe compass' and you're right, it's a simple automotive compass with a suction cup mount.

They are filled with a kind of oil called 'colofonium' or something like that, if my memory serves me right, and should hold quite a lot of pressure underwater as I've seen them on quite a few underwater designs.

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I'm working on a video overlay to display info on screen of heading, depth, temperature, battery status, attitude and GPS surface coordinates based on an Arduino project I'm using for FPV.

Short video clip


If you really want to be sure your compass holds underwater, a diving compass might do the trick, though they are somewhat blukier compared to the one in the video.

They're also in digital form, look on the Amazon webpage.


You might find something inside a cheap survival knife...