One common source of confusion when looking at scanner specification sheets is scanner accuracy. The terms accuracy, precision, repeatability, and noise are often referred to as accuracy and different scanner manufacturers or mobile mapping suppliers can often use these terms to mean different things. Read our Laser Scanning Jargon Blog for more information on technical terms.
Accuracy describes the closeness of a measured value to a standard or known value. For example, if the distance between two points is known and equals 10m and your measurement is 8.5 m for the same distance than it means your measurement is not accurate because it is not close it its true/known value.
Precision, sometimes called “repeatability” or “noise” relates to consistency in results that are being repeated. Using the example below, if you measure a given distance 10 times and get 8.5m every time, then your measurements are very precise. This attribute is independent of accuracy. Your measurements can be precise but inaccurate.
Fortunately, for most scanners the accuracy and precision (noise) are often very similar values, so you could find that only one figure is stated in the scanner specifications. It’s worth mentioning that accuracy can also be described as relative or absolute accuracy.
Relative accuracy can be considered as an accuracy of two points in relation to each other, independent of other error sources. When you compare a distance between two points in your survey to the same distance in the real world you will get relative accuracy. We can think of relative accuracy as a combination of both scanner accuracy and precision.
Absolute accuracy, on the other hand, describes how well your survey is located in the real world. If you pick one point from your survey and compare its coordinates with the real-world coordinates of that point you will get absolute accuracy for this point.
Want to know more? See our Laser Scanning Jargon Blog for more demystifying technical info.