On 3/9/13 6:24 AM, K7LXC@aol.com wrote:
Howdy, TowerTalkians --
If you've ever worked with a crane, a critical distance is from where
the crane will set up to where the load is going. In the past you'd have
to climb roofs or otherwise estimate sometimes blind distances and hope your
estimate is a good one.
I hired a 37 Ton crane today to stand a 60' AN Wireless tower. The
operator took out his Verizon Android smartphone and used an app to help do
his job. He located the site with a Google Maps-type view and marked with his
finger where the crane was going to be set up in the driveway and where
the tower base was. He pushed a button and it told him the distance was 63.26
feet. Cool. This app - he said it was Map Ruler - did it easily and fast.
Being a trailing-edge technology kind of guy, it was news to me plus
being nifty and very helpful. I can see it being used to help site where a
tower will go, measure trench lengths, distances between towers for possible
wire antennas, etc.
Any other cool apps we'd be interested in out there for tower, etc.
stuff?
There's a bunch of theodolite type apps for iPhone and Android. They
seem to be of two kinds.. ones where you point the camera at the item of
interest and others where you sight along the edge of the case. More of
the former now than the latter.
They tell you vertical angle and compass direction, both accurate to a
few degrees.
Some of the theodolite apps will solve for triangles by measuring
multiple angles and knowing the distance or size of something in the
image. (e.g. if you know how long the boom is then you could measure the
height of the tower by measuring the angular size of the antenna).
In general, measurements of angles made between two things in the same
image are quite precise (small fraction of a degree). That's limited
mostly by the camera resolution and the consistency of the optics, which
is pretty good (500 pixels over a field of view of 45 degrees is better
than 0.1 degree)
Angle uncertainty of 1 degree is about 1 part in 60 in distance/width
for small angles.
If you're 100 ft from a tower, and you measure the angle to the top as
45 degrees, and you have +/-1 degree accuracy, the tower is probably
somewhere between 96 and 104 ft tall.
A similar device, but much higher performance, are the Leica Disto laser
distance meters (from about $150 to 400). They'll tell you how far
something is 100m or more away with an accuracy of better than a
centimeter. The fancier ones will measure the angle, so you can turn
slope distance into horizontal and vertical distance. (e.g. makes
measuring the height of a tower or a building trivial)
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