Archive for October 29th, 2012

Recommended Tool: Bosch GLR225 Laser Rangefinder

I’ve been doing some amateur surveying in preparation for the long-awaited driveway paving project, just to see where the property boundaries might be, and this Bosch GLR225 laser rangefinder makes it wonderfully easy to measure distances:

Bosch GLR225 Laser Rangefinder

Bosch GLR225 Laser Rangefinder

It’s good up to 230 feet = 70 meters, which means you can measure a sizable chunk of property in one shot. It reads down to 2 inches with 1/16 inch accuracy / resolution (call it 50 mm and 1.5 mm), so one could use it for setups in the shop. It can solve right triangles, which means you can measure distances with an obstruction in the middle, and has a few other tricks. Other rangefinders evidently have more tricks, but I favor writing direct measurements on paper and making computations based those values, rather than using mysterious results direct from the field that can’t be easily verified at the desk.

I tried measuring the nominal 212 foot distance to the Hudson River from the center of the Walkway, but it reported an error. Most likely, specular reflections from water don’t work well, at least not at that distance.

You can buy retroreflective targets, but the Basement Laboratory Warehouse Wing disgorged what looks like roadside border markers, pre-bent into a useful shape:

Laser targets - normal

Laser targets – normal

Seen by reflected light, they’re much more impressive:

Laser targets - flash

Laser targets – flash

They came with the house, so I don’t know their provenance. What I do know is that I can’t hold the rangefinder steady enough to keep the spot on the target at much more than 100 feet. If I get around to doing much more surveying, I must conjure up a tripod mount; the base has a 1/4-20 socket in an awkward location and can measure relative to the screw centerline. Perhaps a rifle stock with a spotting scope would be handy, too, although I’d certainly acquire another black spot on my record.

If you were going to use it in the shop, you’d want a rotating pivot aligned at the intersection of the tripod socket and sensor port to get a known center point.

You can get one on eBay at a substantial discount, of course…