Abstract
The minimum size of objects or geometrical features that can be distinguished within a laser scanning point cloud is called the resolution capability (RC). Herein, we develop a simple analytical expression for predicting the RC in angular direction for phase-based laser scanners. We start from a numerical approximation of the mixed-pixel bias which occurs when the laser beam simultaneously hits surfaces at grossly different distances. In correspondence with previous literature, we view the RC as the minimum angular distance between points on the foreground and points on the background which are not (severely) affected by a mixed-pixel bias. We use an elliptical Gaussian beam for quantifying the effect. We show that the surface reflectivities and the distance step between foreground and background have generally little impact. Subsequently, we derive an approximation of the RC and extend it to include the selected scanning resolution, that is, angular increment. We verify our model by comparison to the resolution capabilities empirically determined by others. Our model requires parameters that can be taken from the data sheet of the scanner or approximated using a simple experiment. We describe this experiment herein and provide the required software on GitHub. Our approach is thus easily accessible, enables the prediction of the resolution capability with little effort and supports assessing the suitability of a specific scanner or of specific scanning parameters for a given application.
Highlights
Each distance measurement produced by a laser scanner is a weighted average over the footprint, that is, over the surfaces illuminated quasi-simultaneously by the beam
This is the minimum size in angular direction of an object or geometrical feature that can be distinguished within the point cloud [15]
We have developed an analytical expression for predicting and evaluating the resolution capability (RC) of phase-based laser scanners
Summary
Laser Scanning. Remote Sens. 2021, 13, Keywords: terrestrial laser scanning; TLS; scanning resolution; resolution capability; mixed pixel; beam diameter; beam characterization Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// 4.0/).
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