I'd like a tool to measure the height of the neighbours' houses etc
by geometry or trigonometry or drawing triangles on paper,
the sort of thing i see surveyors with on a tripod,
but I dont know what it'd be called.
(It's greek to me)
I dont need anything very accurate and expensive,
so if anyone can tell me the name of what i want,
or better provide a link to a cheap one,
If you use a level and a protractor to get yourself looking up at the
building at precisely 45 degrees from the horizontal - move towards and
away from it until it is 45 degrees, then measure your distance to that
building - the height of the building is that figure, plus the height
to your eyes. All of this assumes the ground is level between you and
We made one in trig lessons at school. Good teaching method as it
brought home the value of learning how to do apparently esoteric stuff
like sines and cosines. ISTR it was something like a cardboard inner
tube from a kitchen roll, gluing a cotton cross-hair over either end,
then a protractor taped to the outside, and a plumbline hanging adjacent
to the protractor - I'm sure you get the idea; you look down the tube
and align both your crosshairs with next-doors' chimney pot, then have
an assistant read off the angle indicated by the plumbline. You measure
the ground distance between you and the neighbours' house wall, and a
bit of trig gives you the height of the chimney. Very rough and ready
- depends how accurate you need it!
You need a clinometer and a measuring tape.
You stand some way back - use the measuring tape to let you know how
far back you are, add of the height from the ground to your eyes, then
use the clinometer to get the angle you need to look at to look at the
height of their gutters.
The use the tangent function to work out the height.
h = tan(x) . d
where x is the angle and d is the distance from you to the base of the
thing you're looking at the top of.
It won't be that accurate as the angle will change slightly with your
height, so to make it more accurate, lie down.
You can make a clinometer with a protractor, bit of string, and some
blu tak. Good picture of a home-made one here:
And if you don't have a scientific calculator or know what the tangent
function is, just walk back from it until the clinometer reads 45 degrees,
then the height is the same as your distance back.
When I was in the Scouts many moons ago we were taught how to measure
the height of trees and buildings using our trusty staves :-)
Simply measure the distance (say 100ft) to the subject, eye on the
ground, stave at 1 tenth of distance, mark off point on stave looking
up at the subject. Then simple geometry to work out height of subject.
Unfortunately not cheap but a Leica Disto basic model will do it
Having now used an earlier model I wish I had bought one years ago. Their
accuracy is incredible.
You can do it with a 1m rule (or any stick of known length) and some
Wait for a sunny day, walk to the end of the shadow of the tallest part
of the building and mark a point. Stand a ruler on that point and mark
the end of the shadow cast by the ruler. Now measure the length of the
rulers shadow and the buildings shadow. The ratio of shadow lengths will
be the same as the ratio of ruler and building heights - and you know
one of them! ;-)
but the ground is sloping unevenly.
But it came to me today whilst driving my car-
if i get a vertical bit of card and 2 tubes pivoting on the card,
then look through the tubes and adjust the angle between them
until I can see the bottom through one,
and the window I want to measure the height of through the other,
mark the angle,
then turn it horizontal and sight from the corner of the house
and remember where the other tube points to along the bottom of the wall
then i can measure from that point to the corner with a tape measure
and that will be the vertical distance
near enough if the ground isnt very slopey...
if my reasoning is correct!
george (dicegeorge) coughed up some electrons that declared:
It's totally over the top for your job I suspect unless you want millimeter
accuracy, but years ago I hired a Leica TotalStation.
That's a theodolite that has a laser rangefinder built in, and a fancy
computer, so once given a direction for north and set up to believe it's
sitting on coordinates (0,0,0) for example, it will give 3d cartesian
coordinates of anything you can point the laser at - in practice, a good
2-3 houses away, without resorting to placing reflectors on the targets.
I was actually helping my father sort out some measurements and I fancied
the excuse to have a go and his (now my) house has some complicated slopes
on the land.
Turns out, now that the data is proving quite useful.
Hire charge was around 100 quid for a bank holiday weekend as no
professional would want it then. Only scary bit was being responsible for
about 3000 quids worth of equipment without insurance! 2 weeks reading the
manual in advance saved a lot of faffing. They're complicated to master the
operational details, and yet powerfully simple to use when compared with
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