Ubil
TUG Member
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?
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?