Balloon mapping - a slightly related question.

[Ron Huber]

Dear friends 

A major energy company, which proposes to set up a very large liquified petroleum gas tank, is going to fly a tethered balloon above the  coastal forest they would build their tank in/on The idea is to show what height (hence how visible) the tank would be, relative to the remaining forest and the adjacent Penobscot Bay, which is heavily used by windjammers and other pleasure sailors.

Question: What is the best way for an independent assessment of the height actually achieved by said balloon?  It will be sent aloft near dawn on June 21st, weather permitting.

Ron

--
Ron Huber
Penobscot Bay Watch
web: www.penbay.org

[Ned Horning]

Ron,

Most any simple solution will use geometry to determine the length of a side of a right triangle. The approach you use depends on the tools you have and assumptions that can be made. If you can measure the angle between the horizon (assuming you are at sea level and want height above sea level)and the balloon using some sort of inclinometer (sometimes built into compasses but you can also make one with a protractor and a string with a weight) and measure the distance from the point directly under the balloon to the point where the angle was measured you can calculate the balloon's height. You can also calculate the height if you have a laser range-finder and can measure the distance to the balloon and measure the angle using the same method mentioned above. If my assumptions are not correct you can apply offsets. If you sketch a picture and draw a right-triangle on it this might make more sense. If it doesn't make sense or isn't appropriate for what you're trying to do let me know and I'll try to explain better or come up with alternative ideas. If you search for methods for measuring tree heights you'll see lots of great illustrations.

Good luck,

Ned

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[Adam Griffith]

I've used laser range finders in the past that do the trigonometry for you.  You just point the laser at the balloon and two distances are displayed, one is the linear distance to the target and the other is the distance from the target to the ground.  They are expensive - maybe $200?  An inclinometer is a much cheaper option.  You can just read the angle (theta) and do the trig yourself.  Remember: SOH CAH TOA

Adam

--
Adam Griffith
Director of Science and Coastal Environments
publiclaboratory.org
828.321.2326

[Jeffrey Warren]

Whatever you do, it might be a good idea to record the process on a continuous uncut video, and also show the readout of a GPS in the video -- and post it on YouTube. Just to show your position so others can verify your calculations. Just thinking of it from the standpoint of evidence.

Jeff

[Todd Huffman]

Perhaps attach a GPS unit to it?  It should be trivial to calculate altitude, and in fact altitude may already be in the data.  Do video and use the time stamps, so make sure they're synced up.

T

[Mathew Lippincott]

I'd skip the laser range finder and use a theodolite.  you may be able to borrow a highly accurate one from a construction company or town planning office, but you can build a pretty decent one with a protractor and thumb-bob.  That last link is to a secondary school math lesson on estimating tree height.  the same instructions should work for estimating altitude.  

All you need to know is 1) how far you are from the base of the object, (two GPS readings, double-checked against a satellite map would be ideal here)  2) the angle between the ground and the straight line from you to the object.

[Patrick Coyle]

 If have iPhone, consider the apps Theodoloite, EasyMeasure, and P&M Measure. Don't know the equivalent ones for Android. Plus a number of the gps apps.

[Scott Eustis]

Android:

GeoCam Free 

is rather data rich, although i think, in general, phones lack precision, this app would generate everything besides the location of the balloon, angle, coordinate

Open GPS tracker 

If you're going to court, i would use a real GPS myself, or at least double-check the phone with other tools. 

scott

Scott Eustis
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[J PT]

Search for "Alti Trak Altitude Finder" in your favorite search engine.

Juan

2012/6/19 Scott Eustis <eust...@gmail.com>