360 degree wind vane angle sensor

I'm putting a wind vane on a car to measure slip angle of the vehicle and I'm looking for the best type of sensor for this application.

Hall effect or other magnetic encoders sound nice due to low physical turning resistance but I'm concerned the vehicle's magnetic field will interfere. A regular old potentiometer would likely work but I'm worried it'll be too stiff to rotate in ~10mph wind.

I only really need 180 degrees of rotation and something weather proof would be nice. Does anyone have a good suggestion of what I could use for this?

I'm concerned the vehicle's magnetic field will interfere

Unlikely, but how do you propose that the Hall sensor detect wind direction?

Google "DIY Arduino wind vane" for lots of examples.

I'm still googling around (irony this thread is now first on that google search you suggested). Most wind vanes I'm finding just give me major cardinal directions.

I was thinking of having the "rooster tail" on a hall effect rotary encoder so that the wind turns the dial. On something like this https://www.amazon.com/BOURNS-6639S-1-103-POTENTIOMETER-ROTARY-10KOHM/dp/B00DDE281O/ref=sr_1_1?ie=UTF8&qid=1495730119&sr=8-1&keywords=Bourns+6639S-1-103

Most potentiometers do not cover 360 degrees, and have end stops, so they won't work to encode wind direction. If you want to go that way, you will need to find a continuous rotation pot (rare).

Consider using an absolute rotary encoder without detents, like this one. Not sure whether that one turns easily enough, but there are models with ball bearings that would work.

This will be mounted to the top of a car. I'm pretty sure it won't be doing 360 spins so even 180 degrees should be more than enough. I didn't think I could find an absolute rotary encoder for that cheap though. I think I'll pick one of those up.

I think I'll pick one of those up.

In fact I just recently ordered one to make a sail boat wind vane.

For decoding, Bourns recommends a 256 byte lookup table, but it is possible to decode with an algorithm, posted here (in PIC assembly language).

I haven't yet written Arduino code for it but will when it arrives.

Great thanks!