When was the last time you worried about a millimetre?

Probably not recently.

But in surveying, engineering and construction, tiny measurements can make a very big difference.

To celebrate National Science Week, we’re taking a closer look at the science of precision – and why surveyors need to be very, very good at knowing exactly where things are.

When close enough isn’t good enough

Surveying combines maths, physics, geography, technology and spatial science to measure and understand the world around us.

And while not every survey requires millimetre-level accuracy, there are plenty of situations where precision really matters.

Here are just a few.

Building a tunnel from two directions

Imagine two teams digging a tunnel towards each other from opposite directions.

Eventually, they need to meet.

That takes some serious measurement.

Surveyors establish precise reference points and continually monitor position, direction and elevation throughout construction, helping engineers make sure the tunnel is heading exactly where it should.

When kilometres of rock and earth separate the two teams, even a tiny error can become significant.

Keeping a skyscraper straight

As a high-rise building gets taller, surveyors repeatedly check its position, alignment and level.

They help construction teams accurately position structural elements and monitor whether the building is behaving as expected as construction progresses.

When you’re building dozens of storeys into the sky, small inaccuracies at the bottom can become much bigger problems at the top.

Making sure the tracks line up

Rail networks depend on accurate positioning.

Surveyors measure track alignment, levels, curves and surrounding infrastructure to help ensure new and existing rail assets are positioned correctly.

Accuracy contributes to safe, efficient and comfortable rail travel – even though most passengers will never think about the surveying behind their journey.

Knowing exactly where your property ends

Where does your property finish and your neighbour’s begin?

It’s not something you want to guess.

Licensed Surveyors use historical survey information, physical evidence, measurements and professional expertise to determine and mark property boundaries.

Those measurements can influence fences, buildings, subdivisions and property ownership – so accuracy matters.

Making sure everything fits together

Major infrastructure projects involve enormous numbers of individual components.

Roads need to connect. Bridges need to meet. Pipes need the correct gradient. Structures need to be built in the right location.

Surveyors provide the measurements and positioning information that help turn designs on a screen into infrastructure in the real world.

So, how do surveyors measure so accurately?

Today’s surveyors have some seriously impressive technology at their fingertips.

They use equipment including total stations, GNSS receivers, laser scanners, drones and sophisticated surveying and spatial software to capture and analyse incredibly detailed information about our environment.

But technology is only part of the equation.

Surveyors also need to understand measurement, mathematics, spatial relationships, errors, accuracy and uncertainty – and know when something doesn’t look right.

Because pressing a button can give you a measurement.

Understanding whether you can trust that measurement is another skill entirely.

Science you can see in the real world

That’s one of the great things about surveying.

Science isn’t confined to a laboratory or a textbook.

It’s being used on construction sites, underground, beside railway tracks, across farms, in cities and even from the air.

Surveyors use science and technology to solve real problems and help shape the world around us.

So, this National Science Week, spare a thought for the humble millimetre.

Most of the time, you probably won’t notice it.

But sometimes, a millimetre matters more than you think.