What do the barometer trend arrows indicate in some of the Watch and iPhone widgets?

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The barometer trends arrows indicate the barometer pressure trend over the past two hours - one arrow per hour. A flat arrow indicates that the pressure change per hour is less than 0.677 hPa (0.02” inHg). An angled up or down arrow means that the pressure change per hour is greater than 0.677 hPa (0.02” inHg) which NOAA defines as being a meaningful change. A straight up or down arrow indicates a pressure change greater than 1.33 hPa or about 0.04”. Note that a drop of 4hPa over three hours often indicates a large storm, so two straight down arrows can likely mean that a drop of 4hPa has occurred or may occur soon.

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What does “alt steady” mean?

 

An “alt steady” status on the altimeter screen shows that the measured altitude is not currently changing. If the measured altitude does change, the status will show the calculated rate of altitude change instead. The altitude and altitude status is calculated with every new pressure sample obtained from the device. The sample rate on the iPhone is about one per second. On the Watch, it is about onc per every three seconds. Note that altitude changes will only only be registered once the altitude has changed by the amount specified by “Climb sensitivity” in options. The “Climb sensitivity” setting lets you ignore very small altitude changes (for example, raising your arm with your Watch on) and also to filter out wind-induced pressure fluctuations that can otherwise be interpreted as altitude changes.

 

What does it mean when I see Watch or iPhone as the source for altitude readings?

 

Both the iPhone and Watch have air pressure sensors that the app uses to calculate altitude. If your iPhone is running in the background (for example, with Live Activities enabled), it will share its altitude calculations with the Watch, and the Watch will display the altitude values that your iPhone is calculating. If the Watch is using its own air pressure sensor to calculate altitude readings, it will indicate that the source of the readings is the Watch. Note that GPS is only used to obtain an initial reference altitude, and it not used otherwise. Using GPS continuously to track altitude would drain your battery very quickly, and the app uses you device’s air pressure sensor instead which is extremely battery-friendly and is also more accuse which is why even the most modern aircraft use air pressure - not GPS - to calculate altitude. The air pressure sensor in your iPhone and Watch can measure altitude differences of just a few centimeters - well beyond what can be obtained with GPS.

 

What does “Standalone” mean on the Watch?

 

The app on your Watch can run completely independently of your iPhone with the Premium Features option. This means that your iPhone is not needed or used to assist the Watch app when it is on this mode. This can be handy if you’re going to be relying on your Watch exclusively for some period of time, or simple want your Watch to be as independent from your iPhone as possible. Note that even without the Premium Features subscription, your Watch will automatically go into standalone mode when it detects that your iPhone out of range of your Watch, and will keep track of barometric pressure and altitude using it’s own sensors so that you’re never left without the data you expect to see. Pretty neat! When the Watch is operating in standalone mode, you will see a small watch icon in the top status lone of the large Watch Alti-Barometer complication.

 

What does the “Alt” setting do?

 

Normally, you do not need to adjust the “Alt” setting. This value is obtained automatically when you open the app using GPS to calculate your initial reference altitude. This is a similar process that pilots and mountaineers use to adjust their altimeters to account for weather based barometric pressure variations. GPS however can have error or may not be available in some situations (underground, for example). The “Alt’ setting lets you adjust the reference altitude manually in these situations.

 

What does the “Refresh alt” button do?

 

Tapping “Refresh alt” will re-start the process of obtaining a fresh reference altitude. During this process, the letters in the button will turn blue, and will show the latest altitude value that the device has obtained. When the process its finished, the button will revert to displaying “Refresh alt”.

 

What is the most battery-friendly way to use the app?

 

Alto-Barometer Pro was designed from day one to be as battery-efficient as possible. For typical barometer pressure trend tracking, you should not see any meaningful battery impact on either your iPhone or your Watch. The app will automatically update in the background about 4 times per hour, and keeps background processing to a minimum. Using the Live Activity/Live Background feature to track realtime data in the background will increase battery consumption since the app will be running continuously in the background while these features are on.Enabled Live Activity will let you see real-time widget updates on your iPhone and Watch. This is particularly useful for continuously tracking altitude. Typically, you turn the Live Activity feature on, and then set the length of time you want the app to be active in the background for the Premium Feature version (there is a default background operation time for the free version of the app). While Live Background is active, the app will continuously record new values for the log every 15 seconds, and will also continuously update the climb statistics. So if you want to accurately track a climb - and perhaps expert the data for analysis - the Live Background feature is the way to do it. The app will automatically result low-power operation once the Live Background time has expired.

 

What does the little info button on the last line of the current conditions data show when tapped?

 

The info button will bring up a popup with a detail breakdown of the cloud layers reported by the weather station. There may be multiple cloud layers reported at different altitudes. This data is commonly used by aviators to determine visibility and which flight rules should be followed, but they also provide an interesting detailed report of cloud conditions. If you’re interested in more detail on how cloud information is encoded into the METAR data that the app reads from weather stations, one good source is https://www.weather.gov/media/surface/SFCTraining.pdf. You can see the native METAR data with contains cloud and other information by tapping the “METAR” button at the bottom of the weather info area.

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