iPhone Barometer

[BazyleParticipant @bazyle]

So does it have a pressure sensor and make a calculation knowing the local weather forecast or use GPS to find where you are and check a map?

[Michael GilliganParticipant @michaelgilligan61133]

I expect this to be my final post on this Topic, Bazyle, so might as well make it a long one.

… I have no idea whether you have installed the App, but if you ever do, then you will find this short essay in the ‘Help’

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Barometer & Altimeter
About
NOT supported due to the lack of an integrated barometer:

iPhones up to iPhone 5S
iPads up to iPad Air, iPad Mini 3
iPhone SE
Watch 1. Gen
Watch 2. Gen
All other and newer devices are supported

Barometer
Barometer uses the barometric pressure sensor and displays the raw data as ‘station pressure’. Barometer also uses the built in GPS to determine your ‘station altitude’. Using the altitude and station pressure measurements, Barometer calculates the barometric ‘pressure at sea level’ (altimeter setting) which is used in weatherforecasts worldwide.

Hint: Horizontally swiping over the graphic let’s you adjust the marker at will!
Tap the barometer and the needle shows you whether the trend is falling or rising.
Longpress on SET allows to set an exact value for the marker.
Tap anywhere on the screen to switch between different displays including the default sea level pressure, marker value or marker date.

Altimeter
Altimeter uses the barometric pressure to determine your change in elevation (relative elevation). It requires a reference pressure setting in order to calculate the pressure and elevation difference. Altimeter also uses a reference altitude. This is the altitude at which the reference pressure was recorded.

 

Warning: The barometric height formula / altimetry contains a lot of factors and can only be exact if you include information such as temperature and a good model for air density. This application uses a simplified formula and assumes an atmosphere with equal air density at every altitude. The calculated values are an approximation! Never use the information from this app in order to make any decisions that require exact knowledge of your altitude! By using this application and acknowledging the warning displayed when you first open the Altimeter you agree that you are aware of this fact and the author can not be held responsible for any damage that is a result of you not using the proper devices in order to determine your altitude.
Trend
This view shows you all measurements stored during the last 30 days. You can choose the displayed timeframe and adjust some settings for this view on the Settings page. There is an interactive timeline included. Simply move your finger over the graph in order to move the timeline marker to different positions. A slightly orange horizontal line is drawn at the current marker value.

 

Important: The app can only record data for the trend when active. It does record new data everytime you open the app, use the “Set” button or bring the widget to display!
Settings
Units: The pressure and altitude units used throughout the App.
Secondary scale: Allows you to show a second smaller scale with a different unit on the Barometer.
Decimals: Different units require a different amount of decimals in order to guarantee enough precision. You can however influence the amount of decimals and either use the default setting or less decimals.
Face: Select a different layout for your Barometer.
Use GPS: For the Barometer and its sea-level-correction it is important to know your height. This enables or disable GPS. With GPS enabled the Barometer screen shows a little indicator telling you whether GPS accuracy is good (green) or poor (orange).
GPS correction: Some users reported their iPhones don’t always get their GPS altitude right and are constantly off a couple of meters/feet. If you happen to know your exact altitude and it does not exactly match what the GPS is telling you, you can enter a correction value here. This will be added or substracted to every GPS reading.
Keep updating GPS: If turned on, the App keeps the GPS active whenever the App itself is active. If turned off, the App will update it’s location only after being brought to front and then deactivates GPS after a few seconds.
Station Altitude: With GPS disabled this sets the station altitude for the Barometer and the sea-level-correction.
Show Marker: Show a little orange marker on the Barometer. This marker can be used to track pressure changes. It is a visual helper only that allows you to see if the barometric pressure has been rising or falling since you last adjusted the marker. This setting also enables or disables the marker line on the Trend view.
Displayed Pressure (Trend): The analog Barometer can show sea-level corrected pressure values (default for Weather usage) or station pressure
Displayed Pressure (Trend): The trend view can (as of now) display two kinds of information: Every recorded measurement corrected to sealevel for better comparison or the raw value of every recorded measurement (station pressure)
Dynamic Y-Axis: By default the Trend view displays the same range that is visible on the analog dial. With dynmaic Y-axis enabled the maximum and minimum displayed in trend view will be calculated from all recorded measurments that are beeing displayed.
Export trend data: This will create a CSV file of all your trend data (last 30 days) and allow you to share or save it using iOS features. Please note the data of the export is saved with pressure and altitude units as selected for the barometer. Exported values are date of measurement, station pressure (sensor raw value), station altitude and sea level corrected pressure.
Clear History: Resets the trend view and deletes all locally stored data. Barometer never uses your internet connection and never shares your recorded measurements with anyone. They are however included in your iPhone Backup.

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MichaelG.

[Maurice Taylor]

On Maurice Taylor Said:

Hi, I assume that nobody knows what pendulista means.

Maurice

It’s word-play, a joke.

The suffix -ista appended to a name or object indicates a fervent supporter or enthusiast.   Therefore a pendulista is someone keen on pendulums, of which there are several on the forum.

-ista has a South American flavour suggesting extremism, picked up from the likes of Peronista, Sandinista and Integralista.  (Argentina, Nicaragua, abd Brazil) The Daily Mail referred to labour party supporters as Corbynistas a few years ago.

In English, the Latin a is usually dropped, giving us words like socialist, fascist, machinist and hobbyist.

Dave

 

[Harry Wilkes]

On Harry Wilkes Said:

So Rob’s at 598 ft who lives higher ?

 

We are at 1040′ in Buxton (317m), off a real OS map; my Android altimeter, on a Google Pixel 3, actually shows 1126′ as I write this, so quite a bit out.
Currently showing Barometer as 1038 mbar whereas our local weather station comes up as 1035 mbar, both corrected to sea level; actual local station pressure at our house is 996mbar, so I guess the actual pressure sensor in the phone is reasonably accurate.
There doesn’t seem to be any way to calibrate the app when you’re at a known height, which seems a bit of a shortcoming.

Bill

[Jouke van der VeenParticipant @joukevanderveen72935]

Why not build your own pressure/altimeter?
A BMP280 or BME280 can be bought for les than £5.

In combination with an, e.g., Arduino processor you can build a nice “weather station” recording temperature, pressure and relative humidity.

Pressure is within 1mbar (100Pa) absolute accuracy.
You can even detect height differences less than 1m (corresponding with approx. 12Pa).

At the moment I am experimenting with two sensors in order to measure pressure differences less than 10Pa.

Of course you have to calibrate if you want to measure “exact” height above sea level.

Regards, Jouke

[Harry Wilkes]

On Harry Wilkes Said:

So Rob’s at 598 ft who lives higher ?

H

🙂 Actually minus 598 ft (the – is very small on my screen too), but after I pressed the SET button, it became a much more believable positive 27

I like the app

Rob

[Jouke van der Veen]

On Jouke van der Veen Said:

Why not build your own pressure/altimeter?
A BMP280 or BME280 can be bought for les than £5.

In combination with an, e.g., Arduino processor  [ you ]    can build a nice “weather station” recording temperature, pressure and relative humidity.

Who, me?

[Bazyle]

On Bazyle Said:

So does it have a pressure sensor and make a calculation knowing the local weather forecast or use GPS to find where you are and check a map?

It could do either, or both.  Most up-to-date Smartphones contain a number of sensors, though not all are necessarily fitted.  Usually though:

• A light level sensor, used to control screen brightness and probably the camera
• A 3D magnetometer, used by navigational apps
• A 3D accelerometer, used by navigational apps, and maybe by the operating system to turn the device off before it hits the ground after being dropped.  Also, which way up the device is for landscape and portraite
• A GPS receiver, getting accurate time, latitude and longitude, plus less accurate altitude.  Again used by navigational apps and the OS knows where the device is.
• A proximity detector
• Air pressure, humidity and temperature environmental sensors.

All sensor data is available to the application programmer.

Apps typically start by asking the OS for a list of supported sensors, so the program won’t read humidity or air pressure unless a physical sensor is available.

Thereafter all the sensor information can be used by the programmer to do whatever his imagination suggests.    A simple App might just read Air Pressure and do a simple uncorrected altitude calculation, assuming a standard value for air-pressure at sea-level.  A more sophisticated App could connect to a remote weather station to find out what the local sea-level air-pressure actually is at the moment, and make the correction.  If a barometer is fitted, report what it says, or connect to a weather station for an estimate.

Most free apps keep it simple, but more can be done.  Barometric altitude could be compared with GPS altitude, and both compared with a map recording ground height at the device’s GPS position.   This could warn that an aircraft is flying dangerously low.  As changing GPS positional data over time also allows speed and direction to be calculated, the App can predict an aircraft is on course to fly into a mountain x miles away unless it climbs or turns.  Or the phone could confirm a landing approach is OK.   The accelerometer reports the device’s yaw, pitch and roll, GPS knows it’s direction relative to true North, and the magnetometer knows direction relative to Magnetic North.

This level of sophistication is normally implemented in air-safety assured cockpit equipment, but much the same, not quite as reliable, can be done with a smart phone or an Arduino plus some electronic modules.  Whilst a smart phone displays information beautifully, a microcontroller can control hardware, so same the technology can pilot a flying machine.   Makers construct Quadcopters, and I think that’s just as much Model Engineering as building LBSC’s finest loco.

Dave

 

 

 

[V8EngParticipant @v8eng]

Well downloading and using this app appears to have turned me into my grandfather!

I find myself looking at the dial regularly and moving that pointer as he used to do with theirs, I suspect he would miss tapping the barometer face though.

[Michael GilliganParticipant @michaelgilligan61133]

Have you tried tapping ut ?

… it works rather nicely

MichaelG.

[V8EngParticipant @v8eng]

Thanks Michael.

I had not tried that.

Now I have truly morphed into my grandad he used to tap the barometer in passing and now find myself regularly tapping the phone one.

 

[Michael Gilligan]

On Michael Gilligan Said:

Have you tried tapping ut ?

… it works rather nicely

MichaelG.

I hadn’t – I like it even more now!

Rob

[Author]

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