Apple Watch May Display Incorrect Altitude Readings in Unusual Weather Conditions

[randyhudson]

How do you place an altimeter inside an air-tight, waterproof watch? If they're using air pressure, I wouldn't be surprised if just pressing on the display caused your altitude to go down.

Also, if it calibrates from GPS, and then calculates deltas from air pressure, wouldn't going into/out of cold weather affect it?

 

[PinkyMacGodess]

How do you place an altimeter inside an air-tight, waterproof watch? If they're using air pressure, I wouldn't be surprised if just pressing on the display caused your altitude to go down.

Just like on a plane. You seal the tube leading to the sensor.

 

[iamasmith]

You are going to get this anyway in rapidly moving weather systems.

1. The barometric pressure is the basis of the Altimeter.
2. Adjustments can be made using GPS Z location but it's perhaps 1/3 as accurate as X, Y and those can be bad enough depending upon the azimuth angle of the satellites you happen to have locked on to.
3. Weather system based correction, such as WAAS or some other A-GPS system that may relay correction data for elevation is subject to the time that the observation station records the change in the moving weather system and then relays it to your device for correction.

You are always going to get some kind of variability with these limitations.

If some other fixed geo reference were available, say short range beacon giving altitude, the A-GPS simply retrieved altitude for the current location from an accurate server then you will have this problem.

The problem then is getting an accurate elevation data that is granular enough to query if you were to adopt the query server approach plus the accuracy may factor you being at the top or the bottom of a cliff, gorge, building etc.

 

[chabig]

Imaagine taking off in stormy rainy low pressure areas like London England, and flying to the notoriously high pressure dominated Caribbean.

That (going from low to high pressure) is safe because the true altitude will be higher than indicated. The opposite (going from high to low pressure) is not.

 

[PinkyMacGodess]

That (going from low to high pressure) is safe because the true altitude will be higher than indicated. The opposite (going from high to low pressure) is not.

Either way, at altitude, planes would be flying at almost any altitude. Many don't realize that plane altimeters are adjustable. One of the first things that a pilot needs to do as they transition to lower altitudes is get the altimeter setting for their destination. It can be radically different than where they left. Operating with a blocked or inaccurate altimeter is incredibly dangerous. Yes the difference in altitude can be really large.

 

[DaveMcM76]

This is pretty normal for a pressure based altimeter... my old casio protrek watch had the same issue but that also had a simplistic form of calibration where you could tell it you were at a known altitude which it then used to calculate altitude changes based on air pressure differences from that known point.

 

[subi257]

It would not in a pressurized one.

Duh, that makes complete sense...I was not thinking logically.

 

[subi257]

It would show the artificial altitude the plane cabin is at (In a pressurized cabin), not the actual altitude the plane is flying at. Plus, given flight levels (see above) the actual altitude is not the same as the flight level, unless the atmospheric pressure is at 29.92 inHg.

In cabin pressure also varies by plane, airline, and route. That's why ears pop. That's why masks come down if there is a pressure drop. Humans can't breath for long at the altitude planes fly at.

Yeah, I was not thinking...brainfart

 

[subi257]

Either way, at altitude, planes would be flying at almost any altitude. Many don't realize that plane altimeters are adjustable. One of the first things that a pilot needs to do as they transition to lower altitudes is get the altimeter setting for their destination. It can be radically different than where they left. Operating with a blocked or inaccurate altimeter is incredibly dangerous. Yes the difference in altitude can be really large.

Yeah, they can do silly things like fly into the side of a mountain....

 

[subi257]

It'll work anywhere there's atmospheric pressure.
Most commercial airplanes are pressurized to about 7,000ft give or take a thousand. So you'd never see the plane's actual altitude with a barometric altimeter in the cabin.
Most commercial airplanes are also made of solid aluminum which is quite effective at blocking GPS signals. If you hold a GPS receiver up to the window you can get a fix, but as a passenger, pinpointing your exact location, altitude or speed is quite difficult with any instruments you may have with you.

Yes, that is why the "flyover" app does not work well in a plane..it's always iffy

 

[PinkyMacGodess]

Yeah, they can do silly things like fly into the side of a mountain....

Commercial planes have ground proximity radar, but it only looks down. *shrug* GPS helps then avoid mountains too. It's a lot safer than it was years ago.

 

[subi257]

And if you were in a non-pressurized one above about 10,000 feet, it wouldn't matter after a few seconds...

Cabin pressurization...

EDIT: Payne Stewart's pilots were incapacitated by hypoxia after a slow leak, apparently, caused a total loss of cabin pressure, and killed everyone on the plane in seconds to a minute. The plane flew on auto pilot until it ran out of fuel and crashed. That has happened several times over the years too. It was a tragedy, but they were dead long before the plane crashed, and probably had no idea it was happening. The pilots likely did, but were overcome before they could react. At altitude, the concentration of oxygen drops with the pressure. We need oxygen to survive.

But I would think that only applies to sudden pressure lose, there are plenty of people that live above that altitude. I spent some time in Quito Equidor at 9700 feet above sea level. I was beat for the first day or two....partly from drinking the wrong water...but after 3-4 days it was like I had always been there. A couple of friends of mine traveled to basecamp at Mt. Everest 17,000...if I remember correctly. They had to acclimatize correctly for a week or so on their way up.....I would love to do that

 

[naboco]

I've been having this issue ever since I took a flight in early Dec., and now the watch shows my altitude in the range of 5300-5700 feet, not even close to my actual altitude of 1700. Which is much further off than the pressure variance would normally account for, or at least that's my understanding.

 

[iapplelove]

Do Europeans measure distance in sports venues?

yes, but soccer fields

 

[ELman]

I have had this issue with my series 6 since day one. I have talked with Apple support multiple times and they are "looking into it". Some days it right on. Other days It can 200-600 feet off. My iPhone does not have and issue. Third party apps like My Altitude seem to work fine on the watch.

 

[4jasontv]

yes, but soccer fields

Two questions. Are professional European football fields a standard size, and aren’t they called a pitch not a field? Bonus question. Would a European ever reference American soccer as a unit of measurement?

 

[subi257]

Commercial planes have ground proximity radar, but it only looks down. *shrug* GPS helps then avoid mountains too. It's a lot safer than it was years ago.

Yes, that is true...I always watch "Air Disasters" and it's amazing how many planes have hit land because their altimeter was not calibrated in advance and they flew into clouds and did not see what was there...mostly in South America and Asia. I love this conversation, because you seem very knowledgable of aircraft. I have a friend/vendor that I work with who has had a pilots license for decades. I'm not sure what ratings he has but, he knows all of the right people and was able to "fly" a Boeing 747 training simulator a few times....the same on the the pilots are trains/certified on....I'm jealous

 

[rotax]

If there is a data connection, the local time sensitive barometric pressure at ground level should be used for correction to improve accuracy. If not, it should be indicated as not corrected for local pressure and allow for a manual entry temporarily until data is available and updated. Also, I presume the measurement is in AGL and not MSL.

 

[PinkyMacGodess]

But I would think that only applies to sudden pressure lose, there are plenty of people that live above that altitude. I spent some time in Quito Equidor at 9700 feet above sea level. I was beat for the first day or two....partly from drinking the wrong water...but after 3-4 days it was like I had always been there. A couple of friends of mine traveled to basecamp at Mt. Everest 17,000...if I remember correctly. They had to acclimatize correctly for a week or so on their way up.....I would love to do that

You can acclimate to the increased altitude, but it effects some people harder than others. Payne Stewart's plane had a slow leak, and eventually they all died from hypoxia. They likely were all dead before they left Florida airspace, as I remember the transcripts. But some cannot acclimate to higher altitudes. My first trip to Denver, I was breathless nearly the entire time, and had pronounced altitude sickness for a week or more afterwards. Since then, I've been working out like a maniac, and lost 60 pounds. My last trip to Denver, I felt totally fine, I even rented a bike and went for a ride up and down the rivers that run through that amazing city. I felt no effects of the altitude, making my prior visit very striking. I was a mess that first visit. If the person is healthy, they can survive longer, but a drop in partial pressure of oxygen, has effects that often can't be tested, they can be so subtle.

 

[deeddawg]

nevermind

 

[PinkyMacGodess]

Yes, that is true...I always watch "Air Disasters" and it's amazing how many planes have hit land because their altimeter was not calibrated in advance and they flew into clouds and did not see what was there...mostly in South America and Asia. I love this conversation, because you seem very knowledgable of aircraft. I have a friend/vendor that I work with who has had a pilots license for decades. I'm not sure what ratings he has but, he knows all of the right people and was able to "fly" a Boeing 747 training simulator a few times....the same on the the pilots are trains/certified on....I'm jealous

'Controlled flight in to terrain'. It happens... I was in pilot training, and discovered that I have a problem with vertigo. It had never happened prior to the week before I was to start 'spins and stalls'. I did an underwater somersault and spent the next week bombed on Meclizine. I showed up for training and told the flight instructor what happened, and he thanked me for owning up to it. Some students, apparently, under estimate the effects of vertigo. Some people have been able to adapt out of it, but others just go though weeks and sometimes months of agony and never get past it. I was warned too that some people that try to overcome vertigo actually trigger continuous symptoms, making their lives an agonizing experience. I gave up. I LOVED to fly. I really felt an incredible incredible loss when I had to quit. Life isn't fair... *shrug*

 

[subi257]

'Controlled flight in to terrain'. It happens... I was in pilot training, and discovered that I have a problem with vertigo. It had never happened prior to the week before I was to start 'spins and stalls'. I did an underwater somersault and spent the next week bombed on Meclizine. I showed up for training and told the flight instructor what happened, and he thanked me for owning up to it. Some students, apparently, under estimate the effects of vertigo. Some people have been able to adapt out of it, but others just go though weeks and sometimes months of agony and never get past it. I was warned too that some people that try to overcome vertigo actually trigger continuous symptoms, making their lives an agonizing experience. I gave up. I LOVED to fly. I really felt an incredible incredible loss when I had to quit. Life isn't fair... *shrug*

I'm sorry to hear that. I know that I could not do that because I can get motion sickness under certain circumstances. Like being in the back seat of a car as opposed to the front seat...driver's side Also stopping or starting too fast.

 

[subi257]

You can acclimate to the increased altitude, but it effects some people harder than others. Payne Stewart's plane had a slow leak, and eventually they all died from hypoxia. They likely were all dead before they left Florida airspace, as I remember the transcripts. But some cannot acclimate to higher altitudes. My first trip to Denver, I was breathless nearly the entire time, and had pronounced altitude sickness for a week or more afterwards. Since then, I've been working out like a maniac, and lost 60 pounds. My last trip to Denver, I felt totally fine, I even rented a bike and went for a ride up and down the rivers that run through that amazing city. I felt no effects of the altitude, making my prior visit very striking. I was a mess that first visit. If the person is healthy, they can survive longer, but a drop in partial pressure of oxygen, has effects that often can't be tested, they can be so subtle.

Yes, it really depends on the individual. Look at the people that summit Mt. Everset with no canned O2

 

[Superhai]

Two questions. Are professional European football fields a standard size, and aren’t they called a pitch not a field? Bonus question. Would a European ever reference American soccer as a unit of measurement?

What’s American soccer, is it different from standard association football?
Technically it is called field of play, but I think the English now refers them as pitch. In Germany they would call it feld. In other languages something different. The size is around 100-110x75-85 m. I have only heard of the use in describing areas, not lengths, which is typically measured in Eiffel towers. 😋

 

[827538]

I’ve been flying a lot recently and after my last flight my Apple Watch is stuck at ~2450 ft when I’m maybe 50 ft above sea level. Previous to this the altimeter seemed very accurate.

I wonder if the altimeter has broken some how. It says it has an error of ~1500 ft. It’s been like this for a week, tried restarting the watch, ejecting water.