Multilevel iOS app

I've initially created this app for myself (repairs, installing new equipment, standing rigging, etc), but later put it on the App Store, in case anyone else might need it.

‎Multilevel: Relative Angle https://apps.apple.com/us/app/multilevel-relative-angle/id6467743326
You can search for "Multilevel relative angle" in the App Store, you should see it right away. Currently only works on Apple devices (iOS 15+, iPhone, iPad). You'll need at least two devices in order to see the relative orientation between the two.
You can also scan this QR Code to get it installed:


In a few words, the app shows you the precise delta (difference) between angles of one (or more) devices, in real time. Bubble level meets Bluetooth — that's all there's to it. You can be on the water, or even in motion, and e.g. perfectly align furniture, stanchions, make things parallel and horizontal, or quickly figure out the existing angle of something like a prop shaft, davits, hatches, etc. It might even be helpful in hull manufacturing — I know many people today still use weights on strings to align bulkheads.

You can also use your macOS machine (Apple MacBook, iMac, etc) and monitor the nearby devices that have Multilevel running on them — might be helpful in manufacturing. An old iPod might work, but I think it needs to be iOS 15.0+, no idea if they can run that.

Anyway, I hope you find it useful. Any ideas or suggestions on how to improve it are very welcome, you're not gonna offend me.

 

Do you zero it to a reference and then it meaures from there?

 

Great question! Short answer: not yet.

I'm trying to wrap my head around how to do that. It's more about calibration, since "zeroing" something could be confusing to the user.
Currently, the app is extremely simple, no settings at all — you just open it on both devices, and it works. You can drag the devices around on the screen to rearrange them, but that's about it. I didn't want to make it confusing to the user (well, myself really). And as for my personal experience using it, there's been no need to zero anything, since measurements are usually performed one-by-one, and it's easy to see the initial difference between devices by laying them next to each other as the first step. If the pitch delta is 1.23º when they're side-to-side, then it's easy to see that it needs to be 91.23º to make one perpendicular to the other, but I totally agree that doing so automatically would be much better.

 

So you need two phones to make it work?

 

Correct: two iPhones, iPhone+iPad, or two iPads... that's how the angles are calculated relatively to one another, instead of being just relative to the Earth's surface. Typical bubble levels are useless on things like boats and cars, since vehicles aren't attached to the ground.

 

Are you actually measuring to .01 degree? How do you mount a phone to maintain that level of precission? As an engineer and a mechanic, significant figures are critical.

 

Smartphones can measure much more precise numbers coming from the gyroscope, but vibration and temperature usually affect those fine values.
It's a 64-bit floating point ("Double") type in Swift programming language, up to 17 decimal places (depending on the value to the left of the point). It's so good that it's bad — various malware is known to utilize gyroscopes as microphones, to eavesdrop on conversations.

I limited the displayed values to just two decimal places — otherwise the text takes up too much space, and it becomes a bit hard to read. I think we're used to reading floating point numbers with two decimal places because of price tags. You can lay two phones running Multilevel down and see that it'll show no change in delta values, but once you tap on one of them, you'll then observe that the delta values change a bit and then go back to where they were.

I'm as OCD as the next guy, but more than .01 is unlikely needed when it comes to boats. I thought of making a setting where it's configurable (none to .00001), maybe I'll do that at some point.

And it's a very good question regarding mounting. I'd say just laying things flat should be enough in most cases. Probably most of the time you can lay the reference device flat (e.g. in the cockpit, where you know it's 100% parallel to the waterline), and then lean another device against whatever you need to measure. a bunch of tape or a phone case with a clamp could help (if you need to do it all the time).