what can make a laser level inaccurate

What can make a laser level inaccurate?

Laser levels are great bits of kit. They provide levels lines for you to work with wherever you are. They are easy to carry around and easy to set up and work with.

But only if they are accurate.

Laser level manufacturers will quote the accuracy of their laser levels, and this can be the main selling criteria. You buy a laser level because you want accurate levels. But do you know what can make a laser level inaccurate?

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What is accuracy?

Accuracy refers to how close the measurement is to the true value. Is the laser level giving an true horizontal or vertical line.

What is precision?

Precision refers to how close repeated measurements are to each other. How many times can we set level lines with the laser level and get the same answer.

What can make a laser level inaccurate?

If the laser level is working within the manufacturers specifications and is calibrated then atmospheric conditions, random errors and mistakes are going to make a laser level inaccurate. As users of laser levels, it is down to us to minimize these effects on the accuracy of the laser level.

Atmospheric conditions affect accuracy.

There are many different types of atmospheric conditions that can affect laser light.

Mist, fog, dust, and smoke will disperse the laser beam with the main affect being to the range that the laser level can be used over. If you can see the laser beam in the air, then it is being reflected and refracted from its true path. This usually has a negligible effect on the accuracy of the laser level, the issue is the decrease in range.

If you are a smoker or a vapor, then it is easy for you to see the laser beam by exhaling in its path. You can check for yourselves if the range is decreased easily and if it has a noticeable effect on the accuracy (the position) of the laser line on the wall or the detector.

The greatest effect on laser level accuracy is heat!

Different areas of air temperature will have a greater effect on the accuracy of a laser level. The greater the difference in air temperature the greater the effect on the accuracy of the laser level will be.

You may think that there is not a great difference in air temperature across a room or outdoors in a field but there can be sources of extreme heat that will affect the laser beam. The one that springs to mind for me is exhausts from machinery working close by.

When light (in this case laser light) travels through air of different temperatures its path is affected. Air of different temperatures has different densities. This has an effect on the speed the light travels through the air and will also affect the refractive index. This is usually imperceptible to us, especially over short distances.

The most well-known effect of light being refracted is the mirage. This is when you believe you see water in the desert that you know isn’t there.

Knowing that light can be bent (refracted) means that we can accept there can be an effect on the laser beam. A rule of thumb would be that the closer the heat disturbance is to the laser level the greater the effect on the accuracy of the laser level.

Try this for yourself by placing a laser level on the mantlepiece of a fire or using a hair dryer or heat gun in front of the laser level and see the affect for yourself.

Real life example of atmospheric conditions on a laser beam.

During June 2020 we had a spell of very warm weather in the UK. During this time, I was laying some drainage pipes with a pipe laser. The warm summer sun warmed up the pipes and affected the laser beam significantly. The atmospheric conditions in the pipe affected the laser beam continuously making the laser dot dance around the target.

The effect on the laser beam surprised me so took a video of it to prove this can happen.

Laser Level inaccuracy due to the user.

Mistakes are from the user of the measuring device and are often only done on a single occasion. These can often be difficult to find as there is usually no way of checking the mistake. For example, reading a tape measure incorrectly or holding the detector at the incorrect height. This often happens when people are distracted or interrupted mid task.

Systematic Errors are from the instruments or equipment we use to take the measurements. Systematic errors are either due to following incorrect procedures or damaged or badly adjusted equipment. These types of errors can accumulate every time a measurement is taken. Systematic errors can usually be identified easily if proper checks are carried out.

Random Errors are errors that are usually beyond our control. These errors are ones that we can’t control and can’t “see”. If we have eliminated both mistakes and systematic errors, then we can identify random errors by repetition of taking the measurements.

Inaccuracy in the laser level detector.

Another potential error source could be from the detector used. Most of the detectors in use today have an adjustable tolerance filter. This means that level mark on the detector can have a range from 0.5millimetres to 5 or 10millimetres. This tolerance is never factored into the quoted accuracy of the laser levels.

For example. A laser level that is accurate to 1mm over 10metres, could be reduced to an accuracy of 5mm over 10metres when using the coarse tolerance range on the laser detector.

Are cheap laser levels accurate?

They can be. But the old adage “you get what you pay for” will always be true. The greater the accuracy required more the expensive the laser level will be.

Buying a laser level obviously purchase cost must be a consideration. But for me it should be the final item to consider. If I was to set a spending limit first then I would have to discount certain features, warranty, durability, and accuracy before looking for a laser level. This may mean that the laser level that I choose for a job may not be accurate enough.

This would mean the work done may not be to the quality required. The work may take longer to do. The work may not match up with exiting features. All of which ultimately will cost you money. Money that you can’t see or account for.

How do you know if a laser level is accurate?

The only way to know if a laser level is accurate is to check it.

As with all measurement instruments, if it is accurate then it should yield the same result when repeated several times. If you can measure a level line from your laser level, time after time, when it is setup in different locations, then it is accurate. If you can’t, then there is an error from either you, the atmosphere, or the laser level.

Checking a laser level is straightforward. There are a few steps to doing the laser level checks properly. It is the same principle as checking a spirit level.

Here is a guide to checking a laser level.

What is the most accurate laser level?

The most accurate laser level that I know of at the moment is the Topcon RL-H5A. The Topcon RL-H5A is a rotating laser level predominantly used by professionals on construction site.

Topcon RL-H5A Rotating Laser Level

Topcon RL-H5A Rotating Laser with 5 Year Guarantee.
Topcon have recently released the RL-H5A rotating laser and RL-H5B rotating laser.  These rotating lasers are the replacement for the Topcon RL-H4C rotating laser, which has been around since mid 2013.
Topcon describe the RL-H5A as being the next generation of Self Levelling Construction rotating laser.  It is straight forward to setup and use, ideal for any construction site and get the workforce to quickly get work started.

Easy To Use.
Setting up the Topcon RL-H5A is easy.  Just setup your stand or survey tripod relatively level (within 5 degrees of horizontal) and put the Topcon RL-H5A rotating laser on securely and switch on.  The electronic self levelling motors will automatically level up the rotating laser for you.  The self levelling motors will set the laser within 10 arc seconds of the horizontal plane.  An arc second is unit of angular measurement.  In the real world at 200m away from the Topcon RL-H5A you would could expect the laser (receiver) to be between 5mm either above or below the level of the Topcon RL-H5A rotating laser.

Large Working Area.
The Topcon RL-H5A has a large working range of up to 400m from the rotating laser.  This gives a working range of up to 800m diameter, or can cover an area of over 502,500m².  This is more than enough to cover the majority of construction sites.
The Topcon RL-H5A has an IP66 rating, which means it is protected against dust that may harm the instrument and it is protected from low pressure water jets.  It also has long battery life with alkaline (4) D-Cell batteries lasting up to 100 hours of continuous use.  This is 2 weeks on site used all day, every day.  Opt for the rechargeable battery pack and the Topcon RL-H5A will last up to 60 hours of continuous use between recharges.

Choice of Receiver.
With the Topcon LS-80A receiver included with the RL-H5A rotating laser, this allows a single user to quickly and accurately complete any construction site job.  You can also receive height alerts and battery status from the rotating laser on the Topcon LS-80A receiver.  Two modes of accuracy are available depending upon the type of work being undertaken with 5 levels of precision being indicated on the LS-80A receiver.  The Topcon LS-100D receiver is an optional extra for this construction rotating laser.
The Topcon RL-H5A is also covered with the Topcon 5 year guarantee, which they say is the best factory warranty in the industry.

If you are looking for a line laser level then the most accurate one that I know of at the moment is the Leica Lino L2-1 with an accuracy of 0.2mm every metre.

Leica Geosystems Lino L2 Cross-line Laser, red, Black, 110 x 60 x 110 mm
  • Innovative Li-Ion concept for long operating time and extra-bright laser lines
  • Li-Ion battery can be replaced with Alkaline batteries or a direct power supply so that the laser is always ready for use
  • With the practical magnetic adapter, the laser can be quickly set up and aligned
  • The warning function prevents serious errors by flashing the laser lines if the laser is not aligned anymore
  • The robust, dust and splash water protected (IP54) housing protects the laser during the rough day-to-day work on construction sites

Here is a table of rotating laser levels ranked in order of accuracy. It doesn’t cover every rotating laser level available, but does give a great idea of the options available.

ManufacturerModelWorking Range
AccuracyWorking Time
(Single Charge)
Current Price
TopconRL-20011004mm at 200m100Hrs
TopconRL-H5A8005mm at 200m100Hrs
Topcon RL-SV2S800 5mm at 200m 120Hrs
TopconRL-H5B40010mm at 200m100Hrs
LeicaRugby 6809001.5mm at 30m60Hrs
Spectra PhysicsLL300S8001.5mm at 30m60Hrs
BoschGRL 500 HV5001.5mm at 30m25Hrscheck current price
Johnson40-65846001.6mm at 30m100Hrs
Johnson40-65415001.6mm at 30m33Hrs
Johnson40-65355001.6mm at 30m33Hrs
LeicaRugby 6105002.2mm at 30m60Hrscheck current price
LeicaRugby 6206002.2mm at 30m60Hrscheck current price
LeicaRugby 640G4002.2mm at 30m60Hrs
LeicaRugby 6405002.2mm at 30m60Hrscheck current price
Spectra PhysicsLL300N500 2.2mm at 30m 90Hrscheck current price
FukudaFRE-102AR6002.3mm at 30m25Hrs
Johnson40-6950L4502.4mm at 30m16Hrs
MakitaSKR200Z2003.0mm at 30m60Hrs
Spectra Physics LL100N3503.3mm at 30m50Hrscheck current price
PacificHVR 505R1523.3mm at 30mN/A
StabilaSTB-LAPR1502406.0mm at 30m80Hrs
HiltiPR 2-HS A12600N/A16Hrs