Light speed: speed and accuracy aside, the question about laser distance meters now is how to put them to work - Laser Distance Meters

Tools of the Trade, Sept-Oct, 2003 by David R. Crosby

I can't count the number of times I've needed the dimensions, square footage, or volume of a room quickly and wished there was a faster way. In new construction, getting measurements with a tape is time consuming. In remodels, taking these measurements can be tedious. The only solution is to put my aluminum clipboard down--not on the piano and not next to the Faberge egg--and pull my tape. The same problem surfaces during exterior applications (minus the egg). Whether you're squaring foundations or measuring siding or concrete slabs, you can pull your tape and punch numbers into your calculator, but it takes time, the occasional helper, and, very often, ladders.

For preparing bids or change orders, tracking work progress, laying out framing modifications, or loading in materials, faster measurements mean saving time. Laser distance meters (LDMs) are the next generation of measuring devices and the first things I've seen that can beat a tape measure.

Test Criteria

As much as I love innovation, before I adopt a new technology it must prove to be better than what I'm already doing. Laser distance meters look promising, offering incredible accuracy (see "How They Work," page 70), one-position measuring, and onboard memory storage while eliminating tape measure acrobatics.

I tested six distance meters ranging in price from about $360 to $495: the CST/Berger LTI Disto, Hilti PD 28, Leica Geosystems Disto Classic (5), Pacific Laser Systems PLS1, Stabila LE 100, and Trimble Spectra Precision HD150. I used them in interior applications to calculate square footage and room volume, and for finer measurements like a kitchen remodel, trim, replacement windows, and new doors. I also tested them in exterior applications to calculate square footage for siding, stucco, and concrete slabs, and for squaring a foundation. I looked carefully for accuracy, ease of measurements, and laser dot visibility. I examined the user interface for ease of operation, too. Finally, I looked for unique features that made measuring faster or easier than using a tape.

Accuracy

I laid out a range using my 100-foot tape with targets at 30, 60, and 90 feet, then positioned all the tools on the same reference line. Since all the tools measure to 16th of an inch or out to two decimal points (except Hilti's, which measures to the 1/32 inch), the slightest variation in how or where I placed a tool relative to the reference line generated fractional discrepancies in the results. Carefully moving each tool right to the reference line equalized the results and illustrated that each of these devices is more accurate than the tools I have to measure them with.

Interior Applications

Inside, I measured distance, volume, and area, and I immediately found that this is where LDMs really shine. I also measured openings for doors and windows and took filler measurements for a kitchen replacement and installing trim. For gross measurements like square footage, each model took measurements far more accurately than necessary and much faster than a tape measure. For some finer measurements, the devices' technology showed limits. Also, I looked at processing speed to see if there were differences in how quickly the devices acquired a reliable measurement.

Square and Cubic Footage. In less time than it takes to talk about it, you can get the square or cubic footage of a room by pressing a few buttons on any of these tools. When taking a measurement from an inaccessible surface, like the ceiling in a two-story foyer or the opposite side of a wide stairwell, all the LDMs in the group worked perfectly and with the same precision.

Doors. On doors, especially big ones like French or sliding patio units, measuring from inside corner to inside corner of the framing with a tape can be awkward. Not so with LDMs. Each unit has a tailpiece that fits into one corner. Next, you aim the dot inside the opposite corner; switch corners and repeat. In about five seconds you know if the rough opening is square or not and how to adjust it. I like Hilti's tailpiece the best here because it really gets tightly into an inside corner. The tailpiece also folds outward to hook onto outside corners. For applications like this, or anywhere else you need an inside-to-inside measurement, the LDMs are a true measuring advance.

Kitchen Layout. For getting fast, accurate wall lengths, ceiling heights, and area measurements, the LDMs again worked better and faster than my tape and allowed me to work alone. But for line-to-line measurements, like between proposed layout lines for an island or for different sized appliances, the units couldn't provide a measurement because the laser had nothing on which to reflect. While the instruction manuals suggest setting up a target, pulling a tape is easier in this case.

Replacement Windows. I used the units to size replacement windows and found the tools limited. If there are jamb liners (or another jamb-to-jamb obstruction), you must measure then add that thickness to the final measurement. The same is true when measuring height: the sashes obstruct the laser.