Ask HN: Why are map apps so bad at figuring out direction when not moving? | Hacker News Reader

Ask HN: Why are map apps so bad at figuring out direction when not moving?

6 pointsicapybara7 comments

When I'm not moving, Google Maps (and similar) are terrible at figuring out which direction my phone is facing. This is particularly annoying if you're just getting in your car and need to figure out which street to turn onto.

Doesn't the map use the phone's built-in compass, which should be reasonably accurate even while not moving? What prevents the app from knowing the phone's orientation accurately while stationary?

Always been curious about this.

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Just install metal detector app or similar, and walk and see what it will show.

For example, near me all shores covered by the metal-concrete structures, and also I seen magnet anomalies on just ordinary streets, looks like there where unstable surface (my district built on sand) and there created underground metal-concrete structure, so road will not break every day.

I also noticed, near large bridges magnet anomalies are largest, and usually are like roots of tree - extend about few hundreds meters beyond bridge itself.

Also exists some other large metal underground structures - pipes for water, for gas, etc.

Problem is that those underground metal where not demagnetized, in civilian building nobody cares, so only in very pure rural locations, you could be sure that nothing will disturb magnetic compass.

At other side, when move, GPS give very reliable direction vector, it is not affected by any magnet anomalies or others, so now nearly all map soft/hard using GPS direction when move and switches to unreliable magnetic compass when not move.

Also interest results shown by GPS test plus, but compared to metal detector, they just show numbers and crazy compass arrow, don't tried to make any conclusions from them, so need dome experience to figure out what you see.

A traditional magnetic compass can be confused by metal (ferrous) objects in the vicinity. Do you have a way of reading just what the phone's compass is saying, as opposed to the output of some software that uses all available information? If you do it would be interesting to check how well the compass works when the phone is in a car and attached as it would be when used for navigation.

Usually moving a phone horizontally in a figure-eight pattern once or twice will give it enough data to calibrate and start working reliably.

An accelerometer might be the only easy way, but often it's used to detect movement. It would work best if your phone is tilted forward, not flat or vertical. Even then, it's unlikely to be exactly aligned to your car - if you're entering the car, then it could well be perpendicular to the car.

A compass will tell north, but it doesn't tell which way your head is pointed.

I noticed this on my previous smartphones, Sony and Huawei, but I don’t have the issue on my iPhone.

Is there a compass in the phone or is this derived from the gps cloud and relative motion? I assume there are accelerometers that let the maps deal with tunnels…

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