I need to find a range finder to teach my students some basic surveying techniques. My requirements:
Must be cheap. I’m a teacher buying this myself.
Range must be at least 50 yds. Not sure what max range I need.
Must work at an angle so for example we can point it at the top of a flagpole to get the length of the hypotenuse.
Any ideas?
Can you clarify this? People pay big money for rangefinders with built in clinometers to correct for slope. Any off-the-shelf rangefinder will give you the hypotenuse.
One of the other big things people pay money for in a laser rangefinder is a filter for using a reflector. Without a filter you can never tell exactly what you are shooting. The cheapest rangefinder I would use, would be around $750.00
The cheapest way to get reasonable accuracy would be to use a compass and clinometer, and then have them pull a cloth tape or a string box. You would then have them correct for slope on each shot with slope correction tables.
In my grade school class, we taped a straw to the bottom of a protractor and hung a weighted string from the little hole in the center. Look through the straw (with the straw on top). Point it at the top of the flag pole and mark the angle where the string is. Measure how far away from the pole you are and with some trig you can find the height of the pole. The Pythagorean Theorem will get you the hypotenuse.
ETA, we actually used it to get a rough idea of how high our model rockets where flying, but it’ll work for this as well.
ETA2, depending on the size of your school, you might be able to get a janitor/maintenance person to confirm it for you (by having them measure it for you). Come to think of it, you could just use one of the hooks to run a string up to the top and measure that on the ground. But I would let the kids do the math first.
<sigh>
I know how to make a device to find angles. Yes it is a protractor with the straw at 90 degrees and a string and a lead sinker. Of course you skip over the exact reason I need a range finder which is to find out how far away you are. The reason I want the laser to measure the hypotenuse is to include some sine and cosine problems.
“some trig” = sine and cosine problems
Keep in mind, I did this protractor thing nearly 25 years ago, I still remember doing it, I could still repeat it and, to this day, it was one of my favorite teachers.
It was a memorable day for me. When people say ‘we’ll never need this stuff’, this shows them why. This is why they need to learn how to use a protractor or use a ruler or understand trig. I’m sure you know how to make a device to find angles, but perhaps your students don’t.
ETA, you’re looking for a rangefinder, something I know nothing about, so I’ll bow out now before this thread gets derailed.
Let’s start off easy. A laser rangefinder will be the easiest to use.
http://www.basspro.com/Shooting-Optics-Scopes-Rangefinders/_/N-1z0ux5o/Ns-p.price|0
they start at about 120 bucks. not sure if that’s in the budget; if not, try ebay.
Then there’s this guy near Denver with an optical device. Doesn’t require batteries, it’s nearby so you can meet, and it’s cheap. Research shows it works 20-400 yards.
Hope that helps.
Coincidence rangefinder is the term for the optical version
Here are some options…
http://www.ebay.com/ctg/Ranging-Rangematic-1000-Rangefinder-/70309820