How do Andoid bubble levels work?

They're using the multi-axis accelerometer in the Android device to measure the tilt. It's used in the same way by games, eg tilt left = turn left, tilt right = turn right.

The resolution is probably limited by the resolution/bit depth of the sensor, probably 10 or 12 bits.

One approach seems to be here:

It's more like the accuracy is limited. Those accelerometers generally show lots of noise in the bottom bits, which allows you to just average the snot out of them. The result is a nice steady reading with a persistent bias that slowly changes with temperature, time, phase of the moon, etc.

I need to measure a one degree slope to one degree accuracy over a 200 foot sight range. Preferably two or three times that resolution.

Is this reasonable with a cell phone?

More at

Presently using an automatic level (A dumpy level with an internal prism) which is sort of painful.

I need to measure a one degree slope to one degree accuracy over a 200 foot sight range. Preferably two or three times that resolution.

Is this reasonable with a cell phone?

More at

Presently using an automatic level (A dumpy level with an internal prism) which is sort of painful.

Why don't you test it? If you have a surface that reads zero, rotate the phone 180 degrees and it should still read zero. Now place a flat board on the surface (test it for flatness) then insert things under one end until you see the reading change. Check that you get the opposite after a 180 rotation, etc. It's not rocket surgery.

Dunno, one degree is pretty low resolution, rougly a 1 in 100 slope, it sounds possible, write some software that overlays an artificial horizon, and angle marks on the camera image, do some tests.

Yeah, much more precise though.

I think he wants a surveyor's level not a carpenter's sprit level.

Wouldn't it be easier to use a surveyors laser and a spinning prism?

A largish protractor and a plumbline ought to work too!

Part of the issue is probably backpacking a bunch of gear while treking through the Gila mountains. It's not exactly a walking trail.

Since Don is researching the history of the area maybe he can beg or borrow a GPS unit from a survey company for a few weekends. Hell, he might find some survey guys that are also interested. From what I have read on his web site it's an interesting surveying and engineering accomplishment.

"They" make the LBT look like a tinkertoy set. Given "they" only had rocks.

Now have 30 canals or fragments and SIXTY MILES of partially cliffhanging canals.

Mind Boggling world class even. Beyond beyond.

Actually, the Gila Mountains are to the North, the Pinalenos to the South.

The Gila Mountains have the original Dilbert office cubicals:

Yes, but the smartphone accuracy sucks. Most Android phones do not have conveniently flat edges. The edges are full of connectors and lumps. Instead, I suggest an electronic level as an inclinometer. For long baseline measurements, one with a laser.

Last November, I had a similar problem. We were moving a mess of large dish antennas (3, 4, and 5 meter diameter) and needed to realign each dish when the move was done. Such C band dishes have -3dB beamwidths of about 1.5 degrees making alignment rather critical. The mounting pipes and platforms were not quite vertical and the equatorial mount was rather complex. Sweeping the sky randomly with a 4 meter dish didn't work. Finding the azimuth was the main problem, but I also needed to set the dish elevation accurately. For that, I used a cheap Craftsman Model 320-48295 torpedo levels. The manual claims +/-0.029 deg accuracy of the vials and +/-0.1 deg accuracy of the digital display at level or plumb.

I originally wanted to use something with a longer baseline but there was no place on the back of the dish to attach anything longer than about 1ft that didn't have something welded or bolted to it. A torpedo level was all that would fit. Once I had my best guess for the azimuth, I set the elevation with the digital level to my latest guess, and after about 6 hrs of guessing and swearing, there was the bird. I don't think I could have done it without the digital level.

Let's see what's inside (while destroying the calibration). The MEMS inclinometer is a MEMSIC MXD2020EL: I hope this helps. If it doesn't work when I put it back together, you owe me a new digital level.

Probably not, but it would depend on the accelerometer that the phone maker chose to use, probably on the algorithm used by the level app, and certainly on the ability to find a reference on the case of the phone that is good to 1 degree.

If you want a toy, use an app.

If you want a measuring instrument, buy a measuring instrument.