Car Compass Interference

[Ubil]

The built-in compasses of both my cars, a 2018 Subaru Forrester and a 2014 Honda CRV, have been acting strangely. Here's what happens.

About once a week I travel north and south on I-81 over the Susquehanna River at Harrisburg. At the end of crossing the Susquehanna on the southbound side of I-81 the compass gives incorrect readings. This does not happen on the northbound side. Even though it is the southbound side of I-81, the bridge is going northwest. The compass is correct, showing NW, until about the end of the bridge. The compass then goes to NE, even though the road has been straight. At this point the road curves to the left. The compass stays at NE for about a 1/2 mile. Then after the road has curved about 40 degrees, the compass will go to N, even though at this point it should be SW. The road is no longer curving and over the next mile the compass will correct from N to NW to W to SW.

I've never noticed this at any other locations. This is not a calibration issue, because it happens on both cars and the compass has correct readings, except at this location.

The most likely cause of this is nearby high-voltage power lines or magnetized rocks. I'll have to look again, but I don't remember power lines at that location. I've searched online, but I have not found any mention of what I am observing. I've checked the owner's manuals which say to do a calibration when the compass is not accurate, but that can not be the problem.

Any other ideas? Has anyone observed this at this location or elsewhere?

 

[Passepartout]

I dunno. But to avoid a whole lot of unnecessary paperwork, drive by where the road goes, and not by the compass. Compass navigation works great for air and waterborne transport. Not so much on roads.

 

[DaveNV]

I'd suggest getting a passenger and a manual compass. When the passenger sees the manual compass going crazy, pull over. Get out of the car, and walk back to where the compass needle goes off. That will tell you where to start looking.

If the compass is wrong for a long distance, like an eighth pf a mile or something, then I'd blame power lines and such. If it's shorter distances, it's more likely something along the roadway.

I have no idea what is really causing the issue. Seems rather odd, though. Good luck!

Dave

 

[dioxide45]

Could there be something nearby that is causing magnetic interference? Perhaps a large power plant or power transfer station?

 

[nomoretslt]

If I go past high tension wires or a pole that has a transformer on it, my hearing aids start squealing. So I agree....it’s probably something electricalish. I didn’t think anyone actually used that compass. I know if we use WAZE while on the EZ pass lanes thru DC on I 95 she goes nuts....she can’t figure out where we are.

 

[plpgma]

I use WAZE and other GPS-type app's to establish a known path for any unknown route I might be taking -- however I always make sure I'm familiar with where I'm going by scrutinizing an old fashioned map beforehand. For whatever reasons, WAZE and other such app's have simply given bad directions from time to time -- so I make sure that I'm never fully reliant on them. As for the car compass -- I use that simply as a novelty item and rarely as a reference tool (except when I'm making sure that WAZE is heading me in the right geographical direction).

With all that being said, I'm also always 'up' for a good head-scratcher -- so will be curious to know if you ever find the actual cause of your compass interference.

 

[Ubil]

This was a curiosity question. Trying to determine why it happens. Since it happens with my 2 cars, other drivers should be seeing it. We use Google Maps for directions, though since I do this once/week the only reason to use Maps is for traffic conditions.

However, when I am going to spend a long time at a new location I like to get "lost", to learn the area. I do reference the compass when I do this.

 

[Ubil]

I'll get a regular hand compass to compare to the car compass. Unfortunately, since this is on an interstate I can't pull over. There is an exit at the end of the bridge, where this is happening. Next time, if I have time, I'll take the exit and see if I can localize the interference.

 

[Brett]

This was a curiosity question. Trying to determine why it happens. Since it happens with my 2 cars, other drivers should be seeing it. We use Google Maps for directions, though since I do this once/week the only reason to use Maps is for traffic conditions.

However, when I am going to spend a long time at a new location I like to get "lost", to learn the area. I do reference the compass when I do this.

I'll get a regular hand compass to compare to the car compass. Unfortunately, since this is on an interstate I can't pull over. There is an exit at the end of the bridge, where this is happening. Next time, if I have time, I'll take the exit and see if I can localize the interference.

OK - I rarely use the compass feature in my Honda