Using a Laser Distance Measure Outside
There is a lot of misinformation about using a laser distance measure outside. So here I will give a short guide to hopefully clear up some of the misconceptions.
Can I use any laser distance meter outside?
Yes, you can is the simple answer. All laser distance measure can operate outside but, and it a big BUT, the reality in the field can be a hit and miss affair literally.
First of all, a laser distance measure works by emitting a laser dot. This then reflects off a surface and the device calculates the distance from that reflection. So the important thing is the device measures to where the laser dot strikes a surface. In order to know where you are measuring to, you need to be able to physically see the dot. Laws limit laser brightness or output and this is pretty much the same globally. Laser distance measure generally has a laser output of less than 1mW (class 2). So one device’s laser brightness is pretty much the same as another. Outside in full sun, you will not be able to see the laser dot more than about 10 or so meters (30 feet). In some circumstances, you may not be able to see it more than 3m (9 feet).
So yes you can technically use any laser distance measure outside, but depending on the distance you want to measure they may do what you want them to do.
So what types of laser distance measures do reliably operate outside?
There are some laser distance meters designed to reliably operate outside. To do this these measurers need to have some method of enhancing the targeting so that you know where the laser dot is even when you cannot physically see it.
A traditional way of doing this is to have some type of telescopic optical viewfinder. Some measurers have this viewfinder incorporated into the device and sometimes they are a clip-on accessory. The principle is much the same as a gun sight. When you look down the sight there is a crosshair. This indicates where the laser dot is even if you cannot see it. The problem with these viewfinders is that they are often tricky to use. You need to try and direct the device at the same time as looking through it and then press the measure button. Using a tripod can help this but it is still a tricky operation.
A newer method of targeting is by using a video camera and screen built into the device. The camera is directed to where the laser is shooting and the screen has a crosshair indicating where the laser dot is. The advantage of this system is you have more control over the direction you are pointing the laser distance measure and more accurate targeting. The disadvantage is that this technology costs more. But if you want reliable measurements outside its the best way of doing it.
How to accurately target an outside laser distance measure over a long distance?
Ok, so we have a laser distance meter with either optical viewfinder or video targeting. How do you get it to point exactly at the position you want to measure? You can get away with holding the device in your hand over shorter distances and when targeting large surfaces. But, for more specific measurements over longer distances, this becomes too difficult. One answer is a tripod and most outdoor laser distance measures can be mounted onto a tripod. A simple tripod with pan and tilt like a camera tripod can often do the job. For even greater control Leica has an adaptor which provides incredibly fine control of up and down and side to side adjustment.
This video from Leica is handy to demonstrate.
What about range?
Will a laser distance meter that says it operates to 150m always measure that distance? The answer is most definitely NO. The distance advertised by the manufacturers is a “UP TO” figure based on optimal conditions. Often in the real world, you may only be able to reliably measure half the specified distance. This is because of the reflective properties of the surfaces you are targeting. For example, a white painted brick wall is far more reflective than the bark on a tree. So for the brick wall, you measure a greater distance compared to the tree. To improve the reflective properties of the surface you can use a target plate attached to that surface. Most manufactures of outdoor laser distance meters also supply targets either with the device or as an optional accessory. Leica Disto, for example, have a large range of targets of all shapes and sizes.
If you are looking at purchasing a laser distance measure for outside work consider, over what distance you want to measure. Over a very short distance then as the basic standard device may suffice. If it’s over greater distance then you will need to spend a little more and get one with targeting viewfinder of one type or the other. Finally, if you are targeting small areas over long distances such as a fence post at 100m (300 ft) you will also need a tripod and possibly a fine adjustment adapter.
For ideas on basic laser distance meters, you can check this post out HERE
The following are suggested outdoor laser distance measures.