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# Measuring a Building's Height With a Barometer

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7/10/2013 07:00 PM EDT

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142 ways
7/10/2013 8:40:17 PM
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Check out http://www.irontowerstudio.com/forum/index.php?topic=2949.0

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Re: 142 ways
7/10/2013 10:13:21 PM
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@rmcgee0: This is great - lots of interesting ideas here - but I hope other readers try to come up with their own before looking at the ones in the link you provided. Thanks for sharing.

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Re: 142 ways
7/11/2013 3:30:14 PM
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You could use the GPS in your cell phone to get the height of the barometer above sea level while it's on the roof, then put it on the ground and get a second reading, then just subtract the two.

-OR-

You could throw the barometer over the building and then calculate the trajectory and the time it took it to land on the other side, but the math required to do that is way too complicated for me to figure out.

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Re: 142 ways
7/11/2013 3:46:28 PM
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@rcurl: You could use the GPS in your cell phone to get the height of the barometer above sea level while it's on the roof...

LOL

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Re: 142 ways
7/11/2013 8:32:17 PM
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Climb the stairs and mark off the height in barometer-length units.

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Re: 142 ways
7/12/2013 10:25:13 AM
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@n1ist: Climb the stairs and mark off the height in barometer-length units.

That would work -- this reminds me of the Smoot as a non-standard unit of length.

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Put the barometer away...
7/11/2013 5:41:02 PM
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So you don't risk environmental contamination from the mercury inside the column (inherent in many of these suggestions), then go down to the local building department and pull the blueprints for the building.

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Re: Put the barometer away...
7/12/2013 10:20:24 AM
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@jhm001: ...then go down to the local building department and pull the blueprints for the building.

But that doesn't involve using the barometer, which is a key requirement for the exercise.

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Re: Put the barometer away...
7/12/2013 12:53:00 PM
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It does involve the barometer, at least insofar as safely storing it and protecting the environment from a nasty mercury spill.

Obviously your sarcasm detector was miscalibrated, as I was commenting on the disastrous toxic exposure risks involved in some of the suggestions (dropping it off the building, launching it over the building, etc.)

Consider it recalibrated (your sarcasm detector, not the barometer).

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Re: Put the barometer away...
7/12/2013 1:18:20 PM
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@jmumford913: Obviously your sarcasm detector was miscalibrated...

It's not been working correctly for some time now -- I think it needs some lubrication in the form of alcohol :-)

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Re: Put the barometer away...
7/12/2013 6:40:30 PM
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Max re: "But that doesn't involve using the barometer, which is a key requirement for the exercise."

Convince the records office clerk that the barometer is actually a very valuable antique watch. Then bribe him or her with the watch to go right away and get the blueprints without delay, so you'll have enough time to stop at a barometer store and buy a new one on the way back to the building site.

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Re: Put the barometer away...
7/13/2013 1:02:37 PM
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Let's try again. first is it an aneroid or mecury barometer? If mecury then it will have a scale. Use that scale as the basis of developing a measuring stick or string. Then use the string to produce a 45 degree right angle triangle, along the top of a table and the height of the string. Then sight the top of the building along the hypotenuse of the triangle. Knowing the distance away from the building you can calculate the height of the tall building. If the building is very tall then it is easy to make both 45 and 60 degree triangles and use them to sight the top of the tall building. Now knowing the distance apart of the two sighting positions you can calculate the height of the building and the distance you are away from it.

If it is an aneroid barometer then make a simple parachute and drop the barometer attached to it from the top of the tall bulding. The barometer and parachute will quickly reach terminal velocity, so have a colleague a couple of floors of easily measurable distance down measure the time it takes to pass him/her and also the total time to reach the ground. The calculation of height is then trivial. This method avoids the problem of the calculation when throwing just the barometer off of the very tall building and a period of gravitational acceleration and then terminal velocity are involved.

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Re: Put the barometer away...
7/15/2013 11:34:33 AM
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@Ron: I do like the parachute idea ... I just like parachutes :-)

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Re: Put the barometer away...
7/15/2013 12:54:28 PM
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Max, if you like parachutes then you could cradle the barometer in your arms and do the jump   PS I really do know how to spell mercury.

Must huury away am watching soccer England women being beaten by Russia. Oops sorry  I mean working at home.

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Re: Put the barometer away...
7/15/2013 12:57:07 PM
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@Ron: Max, if you like parachutes then you could cradle the barometer in your arms and do the jump...

Been there... done that (three times)... now I just prefer to watch others doing it :-)

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The laser or flashlight solution
7/11/2013 6:35:35 PM
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Buy a cheap laser or for that matter any flashlamp with a decent beam. Move some measured distance from the base of the building. Point the laser at the top of the building and measure the angle that the laser/flashlamp is tilted. A simple trig calculation, using the length of the laser and the distance it is tilted, the accuracy can be increased by intercepting the beam a couple of feet from the ground. The tangent of the angle and the distance from the building will allow its height to be calculated.

Best done at night but be careful to avoid being hit by a barometer that some idiot has dropped from the top of the building

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Re: The laser or flashlight solution
7/12/2013 10:22:35 AM
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@Ron: Point the laser at the top of the building and measure the angle that the laser/flashlamp is tilted....

There are many ways to calculate the height of a building ... the point of this exercise is to use th ebarometer in one way or another.

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Will it work in Tibet?
7/11/2013 6:52:34 PM
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Will this ideas work in Tibet? Do you need more processing of data or extra measurement?

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Re: Measuring a Building's Height With a Barometer
7/11/2013 9:20:03 PM
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Max, you may want to lookup one of the Communications Society event I chaired:

http://comsocscv.org/,

Nov 2012: Technologies for Location Determination in Indoor and Urban Environments.

The speaker from NextNav (formerly @Trimble Navigation) does allude to atmospheric pressure measurement as one of the reliable ways (need 10Pa resolution). This can be accomplished by MEMS pressure sensors in a smart phone BUT it needs to be quite precise and must correlate to a reference system.

MP Divakar

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Another Way!
7/11/2013 9:40:25 PM
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Max, I would like to add another: have the students measure the reading on ground floor, and then climb two more floors, take readings in each and get the delta in pressure between floors. Count the number of storeys in the building and use USGS data charts to get the exact height. There will be some minor inaccuracy in this since the pressure drop vs. elevation curve is not linear, quadratic.

MP Divakar

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Re: Another Way!
7/12/2013 10:28:13 AM
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@Docdivakar: I would like to add another...

All Good suggestions. Another one I read was to set stand at the bottom of the building holding the barometer -- remotely detonate an explosion at the top of the buliding -- and measure the amount of time it takes the pressuse wave to register on the barometer :-)

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Correct use?
7/12/2013 12:28:56 PM
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Has anyone mentioned the correct use?  Measure air pressure at bas of building, then air pressure at the top.  Find the difference and use that to compute the altitude...  Of course, you might need to take a trip to the beach to find the presseure at sea level, too...

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Re: Correct use?
7/12/2013 1:16:28 PM
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@Tom-ii: Has anyone mentioned the correct use?

Don't be silly!

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The reverse of that
7/12/2013 6:36:06 PM
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Max, re: "Drop the barometer off the top of the building, measure how long it takes to hit the ground, and use this value to calculate the height of the building."

Many long years ago, I had a summer job working in the glorious Pacific Northwest forests. Part of the job involved climbing fir trees to pick the cones, which would be used in research plantings.

One day a buddy and myself were each in old growth Douglas fir trees, up in excess of 200 feet. To keep ourselves amused while picking, we yelled back and forth between trees to collaboratively use our calculus knowledge to figure out how fast we'd be going when we hit the ground from that height.

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Re: The reverse of that
7/15/2013 11:27:03 AM
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@Duane: To keep ourselves amused while picking, we yelled back and forth between trees to collaboratively use our calculus knowledge to figure out how fast we'd be going when we hit the ground from that height.

You certainly knew how to have fun in those days :-)

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Re: The reverse of that
7/15/2013 1:32:25 PM
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Max - re: "You certainly knew how to have fun in those days"

I'm not convinced I've improved sisnce then.