of the Finger Lakes, Rochester, and Ithaca, NY.
|A rangefinder is a device
that measures the distance to a distant object.
They are used in construction, surveying, and
forestry to estimate distances and are also
quite popular with golfers and target shooters.
The two basic types are Laser Rangefinders and
Optical Coincidence Rangefinders.
Laser Rangefinders cost $300 and up and look like a pair of binoculars or a monocular. They bounce a laser beam off the remote object and measure the time it takes the laser light to travel out and back. You then simply read the distance from the display. We thought they were too expensive and heavy for waterfall work, although if we had found one with a built-in clinometer and compass, we would have been tempted.
The Optical Coincidence Rangefinder we got from www.forestry-suppliers.com was less than $50, weighs only 6 oz. and will easily fit in your pocket. Although it is less accurate and harder to use in low light, it is plenty good for measuring the height of waterfalls.
You sight through an eyepiece and see a double image through the two lenses. You turn a knob which rotates an internal mirror to align the two images and then read the distance from a scale. Our model can measure from 10 yards to 75 yards which is pretty good for most waterfall work.
When you use a rangefinder, try to sight on an object with a distinct vertical edge since this makes it easier to align the two images. A small sapling, stick, or rock at the crest of the waterfall or the edge of the plunge pool works best. If you can't find a vertical edge, try holding the rangefinder vertically and sight on a horizontal edge. Take your sighting three times and then average the results.
Of course, you will need to sight on the same object with the rangefinder that you use with the clinometer to measure the angle.
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Last modified: 10/09/2005