Measure Twice – Cut Once.
We’ve all done it. We have all measured something wrong in the past. Hours of toiling, making your project perfect and then finding that final piece just doesn’t quite fit.
And then that saying annoyingly pops into your head.
Measure Twice – Cut Once.
If it is too long, we may be able to shorten it. But if it is too short, then we most likely we can’t fix it and we must buy it again.
Why do we need to measure accurately?
Whenever we take a measurement, we need it to be as accurate as possible. We need the measurement to be right. But we know that any measurement that we take will have an error associated with it.
We need the measurement tools to be accurate and we need to have the skill to use them.
If we do not have accurate measurements, then whatever we are building or constructing will not fit together. Inaccurate measurement means that the piece that connects two items together maybe either too big or too small.
Measuring twice is one of the ways that we can eliminate some of the errors that are present in all our measurements.
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Knowing what accuracy we need for our measurements?
As a rule of thumb, the smaller the distance measured the greater the accuracy needs to be. It is no good measuring to the nearest inch when only measuring a few feet in total. Whereas, measuring to an inch over 10 yards would in most cases be accurate enough.
The desired accuracy of the measurement is dependent on what we are building or constructing and the size of the building or construction. No matter what it is that you are building or constructing, the accuracy of the work will be determined.
Knowing what measurement accuracy we need is important. It will lead us to selecting the right measurement instrument for the required job.
What is accuracy and precision?
Accuracy refers to how close the measurement is to the true value.
Precision refers to how close repeated measurements are to each other.
What accuracy can you achieve with steel tapes?
Getting accurate results from taping can be more difficult than most people realise. The accuracy that can be achieved is so dependent on how the tape is used and the corrections that need to be applied. The corrections due to tape sag, ambient temperature, tension, and the slope need to be applied.
And this is all dependent on the distances being measured.
Having used steel tapes for accurate measurements, I know that when using a steel tape of greater than 30m there are factors that need to be accounted for. These factors include.
- The correct tension being applied to the steel tape
- The ambient temperature. Steel tapes will expand and contract due to temperature.
- Ensuring that the tape is not subject to sagging.
With a properly tensioned steel tape, and temperature factored in, then at a distance of 30m you should be within 6mm of the true distance. If measuring along a slope and correcting for the slope then you should only expect to be within 25mm of the true distance.
What accuracy can you achieve with a laser tape measure?
You can achieve a much greater accuracy with the laser tape measure than you ever will with a steel tape measure. With a laser tape measure, a 50m measurement should be accurate to within 3mm. Greater accuracy can be achieved with some models of laser tape measures.
The main advantage of using a laser tape measure is that you do not have to account for tape sag or tape tension in your measurement. Therefore, the measurement has a greater accuracy.
And temperature does not have to be factored in most of the time. Laser tape measures use a beam of light that will travel at the same speed in most conditions we carry out measurements in. They measure the amount of time that the laser takes to be sent and reflected to work out the distance.
Benefits of Laser Tape Measures over Standard Tape Measures.
One of the main benefits I find that a laser tape measure has over a standard tape measure is the ability to measure into corners. The other day I was measuring the internal dimension of a window. Using a traditional tape measure, I found it tricky to measure the width accurately. This was because I had to curl the tape into the corner.
But with the laser tape measure, I could accurately measure the width of the window. By placing the laser tape measure on the window and measuring from the rear of the device. I got the accurate width measurement I was after.
Judge for yourself, the pictures below show the issue of using a standard tape measure for this kind of distance measurement. The tape measure I was using does not have a dimension on it for measuring to the back of it.
Another benefit of laser tape measures is when measuring longer distances than 8 metres. Most standard tape measures that recoil only measure about 8 metres. Nearly all laser tape measures will measure distance greater than this.
Using standard tape measures the most one person can measure by themselves will be around about 8 metres. Distances greater than this using standard tape measures will be a two-person job.
With a laser tape measure measuring long distances can be done easily by a single person. we also don’t have to worry about the tape sagging over great distances. this greatly increases our accuracy that can be achieved with distance measurements.
A laser tape measure can also allow us to measure to inaccessible places or help keep us out of harms way. For example, the other day I needed to measure a road width.
With the road still in use and open to traffic using a standard tape measure across the road would not have been the best idea. Here in the UK working or crossing a live road whilst carrying out your duties at work is (in most cases) not allowed. And pushing a physical tape measure across the road would also not be allowed.
If I only had a standard tape measure, then I would not have been able to measure the road width. But I could use a laser tape measure.
For this I used one of the cheap laser tape measures to measure this distance. Using a laser tape measure meant that I did not have to cross the open road or string a tape across the road.
The Three Errors that Afflict all Measurements.
There are three types of errors that will affect any measurements we take. Be it with a laser tape measure or a standard tape measure. These errors are
- Systematic Errors.
- Random Errors.
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. 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.
These different types of errors can have a varying impact on the overall quality of the measurement taken. For this reason, the more accurate the requirement for the measurement, the more time is required for reducing these errors and therefore the longer the process will take.
Conclusion – Laser Tape Measures vs Regular Tape Measures.
Knowing that all the measurements we take are subject to errors we can start to understand why our measurements don’t always work out. The Measure Twice, Cut Once saying helps us avoid the errors that can plague any measurements taken.
Laser Tape Measures have many great advantages over regular tape measures. Will they entirely replace the regular tape measure? No, I don’t think so.
I still use a regular tape measure, sometimes it is easier to use. But I would not be without a laser tape measure anymore.
My favourite laser tape measure is the Leica Disto. I would recommend one of these all day long. I have had one for over 15 years now.
But recently I tested 3 cheap laser tape measures to see if they were any good. I was surprised by how good some of them were and shocked too.
My recommended Laser Tape Measures.
- Precise distance measurement - quicker than using a measuring tape
- You can set it to use different tilt units. Select in the settings “Units inclination” and choose between ° , %, in/ft and mm/m
- Full colour screen and digital Pointfinder with 4x zoom - perfect for outdoor use
- Extremely robust, designed for use on construction sites. IP65 Rating
- Bluetooth Smart Ready so it easily transfers measuring information to other devices such as the iPad and iPhone simply and can be used with the Leica Disto Sketch app
- ✦ PRACTICAL FUNCTION & HIGHER ACCURACY - Measuring range 50m/165ft,accuracy: ±1/16 inch,unit:m / in / ft / ft + in,and distance, area, volume, Pythagoras (indirect measurement), continuous measurement, addition and subtraction, maximum values and minimum, can meet your different needs.With unique 2 Bubble Levels, providing more precise measurement compared to one bubble.
- ✦ LARGE LCD BACKLIGHT SCREEN & Mute Setting - Large backlight screen provides users with a better visibility.Mute setting allows your different needs .With accuracy up to ±1/16inch, the portable laser measure can perfectly finish a measure task ranging from 0.16 to 165 feet. Also 4 interchangeable units among m / in / ft/ ft+in are designed for people with different reading habits.
- ✦ EASY TO USE - Handy and compact mode provide good operating feeling; IP54 waterproof level and dust-proof function protect the laser distance measure to the maximum extent,It's suitable to use everywhere.
- ✦ WIDE APPLICATION - With multiple measurement modes like distance, volume, area measurement, continuous measurement and measurement by Pythagoras, the laser level is ideal for home, construction and industries, especially in large areas such as rooms, apartments, buildings, real estates, factories, warehouses, etc.
- ✦ Package Contents & Warranty - 1*S2 50m/165ft Laser Distance Meter; 2 AAA Batteries; Package Box; User Manual; 30-Day RETURN refund guarantee.