Abstract
Abstract. Mobile Terrestrial Laser Scanning (MTLS) has been utilised for an increasing number of corridor surveys. Current MTLS surveys require that many targets be placed along the corridor to monitor the MTLS trajectory’s accuracy. These targets enable surveyors to directly evaluate the magnitude of GNSS errors at regular intervals and can also be used to adjust the trajectory to the survey control. However, this “Multi-Target” approach (MTA) is an onerous task that can significantly reduce efficiency. It also is inconvenient to the travelling public, as lanes are often blocked and traffic slowed to permit surveyors to work safely along the road corridor. This paper introduces a “Multi-Pass” approach (MPA), which minimises the number of targets required for monitoring the GNSS-controlled trajectory while still maintaining strict engineering accuracies. MPA uses the power of multiple, independent MTLS passes with different GNSS constellations to generate a “Control Polyline” from the point cloud for the corridor. The Control Polyline can be considered as a statistically valid survey measurement and be incorporated in a network adjustment to strengthen a control network by identifying outliers. Results from a test survey at the MTLS course maintained by the Oregon Department of Transportation illustrate the effectiveness of this approach.
Highlights
Mobile Terrestrial Laser Scanning (MTLS) systems have been used for rail and road corridor surveys since approximately 2008 to support a wide variety of applications (Olsen et al, 2013; Williams et al, 2013)
This paper introduces a “Multi-Pass” approach (MPA), which minimises the number of targets required for monitoring the GNSScontrolled trajectory while still maintaining strict engineering accuracies
This paper focuses on the major error source that affects the positioning of the scanning vehicle itself, which is a combination of Global Navigation Satellite System (GNSS) satellite multi-path, changes in satellite configuration, and geoid undulations
Summary
Mobile Terrestrial Laser Scanning (MTLS) systems have been used for rail and road corridor surveys since approximately 2008 to support a wide variety of applications (Olsen et al, 2013; Williams et al, 2013). Current methods for minimising satellite errors require extensive networks of targets, some of which are used to These “Multi-target” approaches have been adopted by public and private road agencies around the world (e.g., Caltrans 2011, Clancy 2011). This paper presents a novel “Multi-Pass” Approach (MPA), which is an alternative method of identifying MTLS trajectory drift caused by satellite errors. Adopting the CP as an observation provides many advantages These include reduced need for preplaced VCTs established to monitor MTLS trajectories, improved accuracies of surveys where a dense network of targets is unavailable, and helps identify issues with the survey control points themselves.
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