Laser rangefinders – How do they work? Which one should you choose?
Laser rangefinders are indispensable measurement tools that come in handy during construction work, renovations, finishing, in the military, forestry, sports, power industry, hunting, agriculture and everywhere else where quick and precise distance, angle, or slope measurements are required. How does this device work and how can you pick the right laser rangefinder?
Here’s what we’ll discuss:
- How does a laser rangefinder work;
- What are the benefits of using a laser rangefinder;
- How do you measure distance;
- Which laser rangefinder should you choose.
Laser rangefinders are the most commonly used measurement tools that enable fast distance measurement and other spatial measurements. It’s not without reason that professionals prefer using laser rangefinders in their day-to-day work over optical and ultrasonic ones.
How does a laser rangefinder work?
Laser rangefinders emit electromagnetic pulses in laser beams via their optoelectronic systems. The laser beam is reflected off the target’s surface and returns to the rangefinder. Next, the rangefinder’s systems process the beam to measure the distance. The device’s system measures distance by analysing the travel time in two planes based on the phase delay of the emitted and reflected EM wave. This method of measurement is used in phase laser rangefinders.
Another laser-based distance measurement method is to directly measure the travel time of the pulse from the rangefinder to the target and vice versa. This method is used in pulse laser rangefinders. There are also laser rangefinders that perform interferometric distance measurements. That is without a doubt the most precise and fastest distance measurement method, but interferometric rangefinders are expensive and susceptible to damage. This makes them unreliable in the field.
Laser rangefinders let you take measurements both indoors and outdoors with 1 mm per kilometre accuracy. Professional construction laser rangefinders can measure distance of up to approximately 150 metres. Long-range rangefinders can measure distance of up to 1500 metres. These rangefinders are mostly used in hunting, agriculture, forestry, and the construction of roads.
What are the benefits of using laser rangefinders?
Compared to their optical and ultrasonic counterparts, laser rangefinders are the most functional and technologically advanced measurement tools. Their main advantage, other than the extremely precise measurements (+/- 1-5 mm per km), is the fact that they can be used by only one person. Optical rangefinders, used to take precise distance measurements at construction sites and in large open areas, require at least two people at once. That’s why using a laser rangefinder lets you reduce staffing requirements and significantly speed up measurement processes.
Laser rangefinders are also less susceptible to errors in measurement caused by incorrect positioning of the tool and other operator errors. What’s more, most professional laser rangefinders are outfitted with electronic alignment aid, automatic calibration function, and offer the ability to take measurements based on the Pythagorean equation or the “painter” function. These tools also let you take continuous measurements, delay measurements, measure the sum or difference of a surface, and measure volume. Advanced processors and clear screens that display measurement results installed in laser rangefinders considerably increase their functionality and usefulness as well as the comfort of everyday use.
How do you measure distance?
Basic distance measurements with laser tools are extremely quick and easy. All you have to do is turn the device on, put the laser dot on a surface, and start the measurement. Most laser rangefinders have an internal memory that stores up to 100 measurements.
The continuous measurement feature is particularly interesting, because it lets you measure the highest and lowest values and then compare the difference in one measurement cycle. Laser rangefinders also enable accurate room measurements. Processors and algorithms quickly calculate the surface area or room volume. To take these measurements, simply select the right option from the device’s menu, measure the length of a surface, and then take a perpendicular measurement. To measure cubic volume, you need to measure the length, width, and height of a room.
Professional laser rangefinders, like the EXTECH DT60M, also let you take measurements using math functions. This function is based on the Pythagorean equation algorithm. It helps the operator measure and object’s height, using two measure points as reference. This is an extremely helpful function that lets you i.a. measure the height of an object simply by moving the laser dot to the top and bottom of that object.
When taking spatial measurements with laser rangefinders, you must remember that laser beams are dangerous to the human eye. That’s why you have to make sure that no one nearby is at danger before you point the laser beam at an object. Moreover, laser rangefinders must be maintained regularly – especially if they’re used in adverse weather conditions.
Which laser rangefinder should you choose?
There are many laser rangefinders available on the market and they are vastly different from one another. Nevertheless, there are several key attributes that you must pay attention to when choosing a professional measurement device that will be used by specialists.
A device’s design and technical parameters should suit the industry, type of measurements, and the terrain and weather conditions it will be used in. You need a specific rangefinder for construction sites or facility measurements, and a completely different one for long range distance measurements in agriculture, forestry, or the power industry. Here are the attributes you should pay particular attention to:
Operating range is a key parameter of each and every laser rangefinder. Most devices for construction – e.g. the AXIOMET AX-DL 100 – offer an effective range of 40–80 metres. More advanced models let you take measurements from as far as 120 metres away. Long-range laser rangefinders offer an even more impressive range of approximately 1500 metres.
The operating range of a laser rangefinder is important, but its measurement accuracy is just as crucial. Most short and medium range rangefinders take measurements with a 5 mm tolerance. However, the most advanced laser rangefinders, like the EXTECH DT40M, ensure extremely precise measurements with a 1–2 mm tolerance.
Laser dot diameter
The diameter of a laser dot depends on the distance from and the type of measured object. For example, the laser dot will be much less visible on wet plaster than on an old brick wall or concrete underlayment. Usually, the laser dots of laser rangefinders have a diameter of 6–60 mm. We recommend using special high contrast glasses during measurements that require prolonged observation of the laser dot.
Minimum unit displayed
This parameter directly affects the precision of a measurement device. The lower the minimum unit displayed, the higher the measurement precision. The most precise laser rangefinders display measurement results in a resolution of 0.1 mm.
IP degree of protection
A laser rangefinder’s durability and resistance to water and dust is of crucial importance while using it in the field. For construction work, it’s a good idea to choose a product with the right IP rating. This will lower the risk of damaging the device in transport and while taking measurements in highly duty or moist environments, as well as during precipitation. The highest quality professional laser rangefinders have IP54 or higher rating.
|AX-DL100||Laser rangefinder; LCD; 40m; Measurement acc.: ±2mm; 120x50x29mm; 126g|
|DT40M||Laser rangefinder; LCD, backlit; 0,05÷40m; Measurement acc.: ±2mm|
|DT60M||Laser rangefinder; LCD, backlit; 0,05÷60m; Measurement acc.: ±2mm|