If you’re new to mobile mapping systems, you might be unfamiliar with the technical terms that companies use in articles and spec sheets use to describe the performance of their systems. Since this can make it difficult to understand how one tool differs from another in areas like accuracy and workflow, this article aims to help by explaining some basic terms.
From an article by Sean Higgins for NavVis.
We’ll cover the two kinds of accuracy used to benchmark a mobile mapping system, the accuracy errors that are common to mobile mapping devices and finish up by exploring the types of error-correction used in mobile mapping workflows. (We’ve also included a few links to articles that explain these topics in more depth.)
LOCAL (RELATIVE) ACCURACY
The accuracy of a point cloud on a local scale. For a mobile scanner, this is the accuracy of a measurement between points in a single location like a room.
The metric is important in determining the reliability of a scanner, because it can show how accurate the dimensions of a room are—an important consideration for applications like scan-to-BIM or generating floor plans.
GLOBAL (ABSOLUTE) ACCURACY
The accuracy of the point cloud on a global scale. For a mobile scanner, this is the accuracy of a measurement between two points that were not captured by the scanner in a single location. For example, the distance between opposite corners of a building.
Global accuracy is crucial when determining the reliability of a mobile scanner, because it highlights the amount of drift error that accumulates in large or complex mapping projects. In other words, it gives an indication about the scanner’s accuracy across the whole building.
It is also known as absolute accuracy, since it indicates the accuracy of the point cloud measurements as compared to their “true” position in an absolute coordinate system determined by a higher order method, like GPS or survey.
For more precise definitions for these terms, and more details about how NavVis measured this metric for its own scanners, see the NavVis VLX Accuracy White Paper.
For the complete article on mobile mapping systems terminology CLICK HERE.
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