Welldrop
Free App
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About Welldrop
Welldrop lets you measure heights/depths using only a coin.
It uses the phone's mic to listen for sound of coin hitting the floor (which means the app works best in quiet environments).
When used correctly (see the guide below), it can measure with an accuracy close to 1/2" (1cm) for heights up to 3 meters. Welldrop is a handy tool for when a measuring tape isn't available or the height to measure is too high for tape.
Theory of operation is simple: you drop a small coin from 0.5cm (1/4") above the edge of your phone. Welldrop will measure the time between when the coin hits the phone and when it hits the ground. Using some simple physics magic, it calculates the drop height.
Welldrop shows the measured height in both metric and imperial systems. Just tap the figure to switch between the two.
Get source code for this app at https://github.com/oxplot/welldrop
It uses the phone's mic to listen for sound of coin hitting the floor (which means the app works best in quiet environments).
When used correctly (see the guide below), it can measure with an accuracy close to 1/2" (1cm) for heights up to 3 meters. Welldrop is a handy tool for when a measuring tape isn't available or the height to measure is too high for tape.
Theory of operation is simple: you drop a small coin from 0.5cm (1/4") above the edge of your phone. Welldrop will measure the time between when the coin hits the phone and when it hits the ground. Using some simple physics magic, it calculates the drop height.
Welldrop shows the measured height in both metric and imperial systems. Just tap the figure to switch between the two.
Get source code for this app at https://github.com/oxplot/welldrop
All Application Badges
Free
downl.
downl.
Android
2.2+
2.2+
Android app
App History & Updates
More downloads Welldrop reached 1 000 - 5 000 downloads
What are users saying about Welldrop
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by T####:
by T####:
tl;dr: Takes a few minutes of practice, then gives surprisingly accurate heights... plus it's fun / novel! - - - The physics this depends on is pretty precise, so expect to be off by several inches / cm until you've spent at least a few minutes (perhaps four dozen drops for me) practicing the precise angle and position to drop the coin from---work from a carefully measured height and try to get the app to display the precise distance by varying only dropping technique. (Note that the height is to the top of your phone, not the bottom (i.e., *not* height of the surface on which it rests). - - - The good news is that once you get a sense for the technique, you'll be able to judge if a given drop fell correctly or if it was off the model. I just tried it for the first time a few minutes ago and I'm consistently seeing my reading clustered within a half inch of the true height. It's hardly a tape measure, but considering how indirectly the phone measures the height (and that, for large distances, this can be practical where traditional methods are not feasible), this is a very impressive little app!
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by H####:
by H####:
It measured the height of an A4 paper 30cm. Very impressive!
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by T####:
by T####:
Great app!!!!
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by T####:
by T####:
Wrong reading
by Y####:
I'm practicing to make myself compatible with the app.