General model for estimating range variances of terrestrial laser scanners based on (un-)scaled intensity values

TL;DR

This paper develops a methodology to accurately estimate the range variances of terrestrial laser scanners by analyzing raw and scaled intensity data, enhancing the stochastic modeling of measurement uncertainties in geodetic applications.

Contribution

It introduces a new approach for measuring and estimating TLS range variances using intensity values, improving the construction of variance-covariance matrices for better uncertainty modeling.

Findings

Effective estimation of range variances from intensity data

Validation on water dam surface data

Enhanced stochastic model for TLS measurements

Abstract

Recent advancements in technology have established terrestrial laser scanners (TLS) as a powerful instrument in geodetic deformation analysis. As TLS becomes increasingly integrated into this field, it is essential to develop a comprehensive stochastic model that accurately captures the measurement uncertainties. A key component of this model is the construction of a complete and valid variance-covariance matrix (VCM) for TLS polar measurements, which requires the estimation of variances for range, vertical, and horizontal angles, as well as their correlations. While angular variances can be obtained from manufacturer specifications, the range variance varies with different intensity measurements. As a primary contribution, this study presents an effective methodology for measuring and estimating TLS range variances using both raw and scaled intensity values. A two-dimensional scanning approach is applied to both controlled targets and arbitrary objects using TLS instruments that provide raw intensity values (e.g., Z+F~Imager~5016A) and those that output scaled intensities (e.g., Leica~ScanStation~P50). The methodology is further evaluated using field observations on a water dam surface. Overall, this work introduces a comprehensive workflow for modeling range uncertainties in high-end TLS systems.