iOS vs Garmin elevation question

Also a second question. I also see that the elevation in Compass is a one time per open display.
Is there any way to get it to update, say maybe once every few seconds???

I can rarely get two GPSr's running side by side to agree on elevation. I would imagine the same would be true with a smartphone if it uses the same satellite data. If the phone (or GPS) uses barometric pressure to determine elevation, it's accuracy will depend on where the initial atmospheric pressure setting was made.

One will always be more accurate than the other but it will vary depending on location and topography.

If your compass app doesn't display real time elevation, I'm sure you could find one that will.

Seeing that I had to be spoon fed to get the Long/Lat and then Elevation to display....... In the first part....
Can you confirm that the Compass in iPhone does not have an option for real time elevation, and is just a one time calculation based on when APP was started?

The compass feature, which is part of the "Extras" app that came with my iPhone 7+ does not display real time elevation. It reads the elevation when the app is first activated and does not change. When moving, you have to reboot the app to get the current elevation. This may not be the same version you have on your phone though.

My app does not have an option to change the reading to real time.

I did an experiment comparing elevation readings on the iPhone app to my Nuvi 3597 and Montana handheld. I know the exact elevation of my home location is 1252' The iPhone reads 1270' and the 3597 varies between 1283' and 1295' The iPhone is considerably more accurate. I suspect it's because it uses barometric pressure to compute altitude instead of GPS data. The elevation reading on my Montana hand held is 1263'. It uses the barometric method.

There are many apps available, such as "My Altitude", that will give you real time altitude readings. It's free at the app store or for $.99, you can kill the ads.

Other apps give you more or less information so you might want to do a search first.

https://itunes.apple.com/us/app/my-altitude/id465262694?mt=8

Be aware that the readings on these devices represent height above mean sea level, not height above the ground. When driving, this isn't relevant but can be important when using these devices while flying.

Hopefully, this helps with your questions.

Just to make sure. NEVER use any device not approved for airplane as reference if you are flying as pilot! Difference of 100 feet when flying can be deadly. Same applies to pressure based height reading. In airplane, when you doing preflight checks, you are setting pressure for particular airfield and when you getting ready to land you will get pressure data for destination airfield. That's your reading. Only total idiot will try to set or correct airplane instruments according to consumer grade GPS data.

I just wanted verification that it was or was not compatable with real time, via another setting I didn’t know about.......

And Oh yes, you all have NO CONCERNS that I will EVER fly a plane!!