{"id":3654,"date":"2020-04-04T13:34:35","date_gmt":"2020-04-04T11:34:35","guid":{"rendered":"https:\/\/topo4d.be\/understanding-accuracy\/"},"modified":"2026-07-17T10:02:35","modified_gmt":"2026-07-17T08:02:35","slug":"understanding-accuracy","status":"publish","type":"post","link":"https:\/\/topo4d.be\/en\/understanding-accuracy\/","title":{"rendered":"Understanding Accuracy"},"content":{"rendered":"\t\t
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Understanding Accuracy<\/h1>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Understanding accuracy might seem like something strange. In GNSS measurements, for example, there is always a small deviation. Therefore, we do not yet know how accurate the survey is, or whether we are talking about relative or absolute accuracy. When does each apply? In this post, we explain it briefly. <\/p>

Why understanding accuracy is important. <\/strong><\/h2>

Common terms that are important for most topographic instruments are relative accuracy, absolute accuracy, and precision. This blog is intended to highlight why accuracy is important. Simply put, if you understand the accuracy and the factors that influence it, you can achieve the best results with your surveys. <\/p>

Working from the whole to the part<\/strong><\/h2>

A question often asked of land surveyors is: what is land surveying and what do you actually do? And I will be honest, it is a difficult question to answer! As a surveying nerd, I want to tell them everything about GNSS, geoids, coordinate systems, technology, and helping clients solve problems through the use of accurate data. <\/p>

Land surveying is both the science of accurate measurements and spatial data collection, and the art of processing that information into a high-quality end result to best serve the client. As land surveyors, we are trained in many things, but the most important is understanding accuracy, precision, and performing high-quality measurements. Like any good surveyor, I will approach this subject as correctly as possible. In our professional terms, this means setting up a sound system with precise control to ensure that measurements are taken with high accuracy. <\/p>

What is the difference between accuracy and precision?<\/strong><\/h2>

Accuracy and precision are two ways in which land surveyors think about ‘errors’.<\/p>

Accuracy:<\/strong> Accuracy refers to how close a measurement comes to the true value.Precision:<\/strong> Precision is how close multiple measurements are to each other.<\/p>

Example: Shooting at a target<\/strong><\/h2>

A classic way to demonstrate the difference between precision and accuracy is with a target. The measurement process is ‘shooting at the target’. The ‘measurement’ is where the bullet lands on the target. The ‘true’ value is the center of the target. <\/p>

Precision:<\/strong> if all bullets hit very close to each other, but far from the center, there is precision, but no accuracy.
Accurate:<\/strong> if the bullets are approximately equidistant from each other and equidistant from the center, there is mathematical accuracy because the average of the arrows is in the center. This represents data that is accurate but not precise. However, if you were actually shooting, this would not count as a bullseye!
Accurate and precise:<\/strong> if the bullets land in the center and are close together, there is both accuracy and precision.<\/p>

Not all accuracy is equal: accuracy can be associated with relative and absolute positioning<\/strong><\/p>

There are a few other terms that are important for understanding positioning accuracy. These are: <\/p>