iPhone built-in compass not that good?

[Rex Sanders]

Nick Gatel tested the accuracy of his older iPhone SE compass for telescope pointing, with disappointing results:

http://popupbackpacker.com/how-accurate-is-an-iphone-compass/

“Out of five different measurements I never got the same reading twice. The variance was a total of 8 degrees — totally unacceptable.”

He repeated the tests in other locations, and got similarly bad results.

Since the same internal compass is used to orient mapping apps like Gaia, this is potentially bad news. Especially if GPS is acting up.

Has anyone else tested their iPhone compass? What did you find? Are newer models better?

And is 8 degrees of variance actually bad for mapping apps? Depends on how you use them.

When I use mine, it’s mostly to figure out which of several branching trails to take from a poorly-marked junction. No big problems so far.

— Rex

[Jerry Adams]

my old dedicated Garmin GPS compass had the same problem – inaccurate and not repeatable

my Samsung S9 has a pretty good compass

if I look at my track with gaia, then I can see which direction I’m going.  Any GPS with a map and track

[Dale Wambaugh]

I have bought a couple dedicated electronic compasses and found them lacking. I have only used the iPhone compass for gross directional orientation. In many environments it starts a fresh calibration sequence. Note that the compass settings can number set for magnetic or true north which could account for a significant error, but that should be consistent per the local declination

I wonder about interaction between the iPhone compass and GPS apps. I’m doubtful that happens. GPS takes care of that. The iPhone compass does give GPS coordinates too.

I always carry a map and compass. I carry a small compass when doing urban travel too. You know Murphy’s Law, right? Well Murphy loves electronics. Stuff fails, gets dropped, batteries go dead, or just doesn’t work right.

[Bill in Roswell]

Rex, thanks for bringing up this topic. I’ve only casually used the 3D Compass app on my Samsung S9. I calibrated the compass per directions, rotating a vertical figure 8 while rotating my body 360 degrees in the horizontal plane. I placed the phone next to my dev. corrected Silva compass in a wooden table next to the sunroom windows. The arrows lined up exactly. I believe that calibrating the phone compass is critical. My phone was off 12 degrees before calibration.

[Jerry Adams]

I calibrated my dedicated Garmin GPS several times.  It was just as inaccurate each time.

I have a zipper pull compass/thermometer that I leave on the outside of my backpack.  That’s pretty good.  Maybe this is a case where old technology doesn’t need to be improved on?

[David Thomas]

I appreciate that a smart phone has a compass on it, but only as a backup or when I wasn’t planning on using one.  And I’ve used it on dark cloudy nights when I get turned around in the woods or a strange city.

But if I expect to be crashing around off-trail in the fog, then I’ bring a button compass on top of my trekking pole or a wrist-strap orienteering compass straping outside my parka on my wrist so I can look at it frequently while using no hands and no battery life to do so.

[Nick Gatel]

I usually travel cross country in desert canyon country. The lack of water and inaccurate navigation could be deadly. And, at times, sometimes my map & compass skills get rusty. So there are now yearly practice sessions for me.

I just posted another article about the accuracy of the Cammenga Lensatic Military Compass.

My “navigational” target in this new post was 2,300 trillion miles away ;-)

[Nick Gatel]

I calibrated the compass per directions

I did the same between each reading on my iPhone. I also set the compass setting to “True North.”

I also checked the iPhone compass’s Lat & Long readings. They are accurate within a couple arc minutes.

I did not check to see if magnetic north was accurate, mostly because I don’t care where magnetic north is.

[Nick Gatel]

Years ago I played around with an iPhone 4 on a couple backpacking trips. I didn’t check the compass accuracy, but the map location function on my app (Topo Maps for iOS) was pretty darn good.

So if one needs to know where they are, I think most of these smartphone apps are fairly reliable. For cross country navigation I wouldn’t even consider using one.

I don’t use any kind of electronics for backcountry navigation, but, all in all, there is a lot of good to be said about them.

I think the important thing is, if you need to actually navigate cross country with a map and compass, and you haven’t done so in a long time (or really don’t know how), then you might be in trouble.

Also, unless there is a lot of snow, it is pretty easy to hike the entire JMT, PCT or Appalachian Trail without a map and compass, by just using a smartphone.

[Jerry Adams]

How do you align the phone to that accuracy – arc minutes?

With a Brunton compass I used for geology class, there were two pieces of glass (?) that flipped up, with a line on them.  You could look through them and align the lines with some geological feature and get the angle pretty accurately

[Nick Gatel]

How do you align the phone to that accuracy – arc minutes?

Jerry, the phone is getting the latitude and longitude coordinates. It pulls from cell towers and probably the reported location if the phone is connected to the Internet. In the back country it relies on GPS satellites. The phone is pretty accurate do this. But pointing to north — not so good.

[Nick Gatel]

With a Brunton compass I used for geology class, there were two pieces of glass (?) that flipped up, with a line on them.  You could look through them and align the lines with some geological feature and get the angle pretty accurately

That was probably a lensatic compass.

[Jerry Adams]

I was just looking at Google

You flip up a mirror with a line on it, and a metal sight like a gun.  There are bubble levels to keep the compass level.  Rotate the mirror until you can see the feature.  Line it up.  Look at the compass to see the angle to magnetic noth.

Then repeat with another feature and subtract the two angle messurents to get the angle between them

It doesn’t matter what magnetic North is, its just the relative angle you care about.

Anyway, to measure sn angle accurately you need the two sights.  And the bubble level

[Jeffrey List]

I have no info on the iphone compass, but beware that the magnetic compass in the Garmin GPSMAP 66i  (the fanciest inReach device) is absolute junk.

My first 66i unit had compass errors that ranged between -35 and +31 deg, depending on which direction it’s pointing. This is after multiple, supposedly successful, calibrations,  and ensuring I was far from any magnetic interference.

After chatting with Garmin support, they had me return it to REI for a new unit.

The new 66i is better, but still has errors that range from -4 to +16 deg, still obviously horrible for off-trail navigation. (E.g., standing in the middle of dense forest, trying to figure out which way to proceed to follow a track on the screen. The unit will switch to a GPS-based compass when you’re moving, and it seems quite good because the GPS seems quite good, but that’s not too convenient when you’re hanging on to a 45 deg slope.)

So after two units, I’ve given up on expecting the 66i compass to be worth anything. I really just take the 66i as a backup for navigation using my phone, but in extreme cold, or extreme wet, or if my phone dies, the 66i will be relied on to get out and having a bad compass is an issue (although of course I have an analog compass along as well).

Incidentally, my old Samsung S7 android phone has compass errors on the order of plus/minus 2-3 deg, barely measurable in my testing method.

So the question is, how is it that the compass in the REALLY expensive Garmin GPSMAP 66i is WAY more inaccurate than the compass in an ancient Samsung phone??

[Jerry Adams]

Those Garmin stand alone GPSes are archaic dinosaurs

They have no chance against phones.  The phone market is much bigger so they can afford to better design them

I am still holding on to my Garmin 60csx because I’m a hoarder.  I’m almost ready to give it to the Goodwill.

[Author]

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