[NatureNS] Determining Elevation the hard way

Date: Sat, 10 Feb 2007 09:18:13 -0400
From: Jamie Simpson <jsimpson@win.eastlink.ca>
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&gt; Now 
David

Last year my vacation project was a potato cannon.  This is definitely a 
candidate for 2007.

JS

----- Original Message ----- 
From: "David & Alison Webster" <dwebster@glinx.com>
To: <NatureNS@chebucto.ns.ca>
Sent: Thursday, February 08, 2007 4:26 PM
Subject: Re: [NatureNS] Determining Elevation the hard way


> Hi Steve & All,                Feb 8, 2007
>    It is curious how one question will often disclose the answer to 
> another question. Jamie's question has solved the Oak Island mystery. i.e. 
> the so-called money pit shaft was dug by a coconut-mat salesman who 
> wondered how high his house was above sea level and had only a shovel and 
> a rope for tools.
>
>    Your formulation looks good but I would expect instrument error to be 
> large & have consequently looked at a second approach; an improvized 
> differential water manometer. At least that seems like a reasonable name. 
> Having never used or made anything similar, it would be best to check this 
> method out before using it to establish runway elevation for instrument 
> landing purposes.
>
>    Theory: This procedure makes use of the change in air pressure with 
> elevation. At the initial elevation (house or mean sea level as 
> convenient) water height in a transparent U-tube (both arms the same) is 
> recorded just after one end is closed to the air such that air volume of 
> the closed end is not changed. As rapidly as possible (to avoid 
> temperature changes) the unit is moved to the other location (mean sea 
> level or house) and the height of water in the two arms is recorded. If 
> the initial point is not about half way between the two final points then 
> there has been a change in water volume or enclosed air volume due to 
> temperature changes and it may be desirable to start again. As a rule of 
> thumb, a 5 cm difference from sea level would represent an elevation 
> difference of about 3.9 metres.
>
>    [DIGRESSION: If I have thought this through correctly, the difference 
> in water level between the two arms will slightly or seriously 
> underestimate the difference in air pressure between the two locations, 
> because change in volume of the air on the closed side will change air 
> pressure on the closed side. A smaller air pressure on the closed will be 
> increased and a larger pressure on the closed side will be decreased by an 
> amount proportional the fractional change in volume. It might be possible 
> to correct for this it one had to. ]
>
>    From observed difference (h; cm) in water level between the two arms 
> (ignoring the bias described in DIGRESSION) and assuming a temperature of 
> 4o C, one can estimate Z, elevation (cm) above mean sea level using
>
>    Z= (ln po- ln p)RT/g
>
> where ln is natural log, po is pressure in dynes/cm^2 at sea level 
> (1,013,250), p is pressure at the house (1,013,250 -(h x 980)), R is 2.87 
> X 10^6, T is 277o K and g is 980.
>
>    Materials: One McGyver scrap pile, or considering component parts, a 
> valve stem from a bicycle innertube, pine board about 3" wide and 8' long 
> or equivalent (hinged or in two sections so it will fit in a car), duct 
> tape, tacks, about 6' of 5/16 ID tygon tubing, hot water bottle with enema 
> tube, ruler or metre rod secured to middle of board at eye level, rabbit 
> wire, nail, spring clamp & calculator.
>
>    Preparation & Construction: Wash the inside of the tygon tube 
> thoroughly with hot water and dish detergent, heat one end in near boiling 
> water, spread if necessary using a tapered stick and insert the valve stem 
> (previously cut from the inner tube) business end out. Moistening the tube 
> with glycerine will help.
>    Boil several cups of water for at least 2 minutes (to remove dissolved 
> air), add a drop of dish detergent and pour into the hot water bottle 
> quickly but avoid entrained air (e.g. by funnel with bottle suspended in 
> cold water), purge any air trapped from the bag corners, tighten enema 
> tube stopper, fill enema tube with water slowly from below and store in 
> fridge after cooling in cold water. Ideally, to avoid fussy temperature 
> adjustments, the water should be at about 4o C when used and measurements 
> should be taken when weather is about 4o C.
>    Secure valve stem end of tube above board end using duct tape and 
> tacks. The tube section at ruler level should lie near the ruler edge. 
> Fasten rabbit wire to the other end to facilitate water addition. Remove 
> valve stem insert entirely or have it very loose and add water to wire end 
> of tube from below using the enema tube and water bottle. Adjust water 
> level to near middle of ruler, wrap wire of wire end over nail & clamp 
> wire to board. Tighten valve stem insert and press pin in gently, if 
> necessary, so pressure (water level) of the two arms is equalized.
>    As described previously, record water level, move quickly to the second 
> location and record level in the two arms.
>
>    For elevations above sea level up to 10 to 15 feet this might work 
> fairly well. Do try this at home (basement to attic) and let me know what 
> happened.
>
> Yours truly, Dave Webster, Kentville
>
>
>
>
>
> Steve Shaw wrote:
>
>> Y 
>> ........................................................................ 
>> .<...................>  house level
>> |      .        ,
>> |              .         ,
>> |                      .             ,
>> H                              .                   ,
>> |                                       .                     ,
>> |                                               . 
>> ,
>> |                               .                            ,
>> 0末末末末末帽1末末末末末乏1末末末末末帽2末末末末末R2
>> 
>> < - flat  beach level  ->
>> I agree with Paul, you need a GPS but also at least one angle;  but, if 
>> you must try to do it the hard way:
>>    In the diagram above (hoping it doesn't wrap-around on your monitor 
>> display) your house is at 'Y', at height 'H' above beach level, which 
>> projects vertically down below you to point '0' at beach level.
>> Tools: get out your builder's spirit level (set it up horizontally) and 
>> your telescope, and duct tape a straight stick to the telescope to use 
>> as an angle pointer.   Set the telescope exactly horizontal, then  rotate 
>> it downwards to focus on a nice prominent beach rock visible on  your 
>> beach at 'R1'.  Measure the angle of declination (rotation) with a 
>> simple protractor, then calculate (90-this angle), to finally get a 
>> number for the angle (0-Y-R1) =  call it angle A1.
>> Re-level the telescope and rotate it down again to focus it on a more 
>>