Use of small sphere targets to georeference Terrestrial Laser Scan, Photogrammetry and Total Station point clouds within a rail corridor environment

Whiteley, Jason (2018) Use of small sphere targets to georeference Terrestrial Laser Scan, Photogrammetry and Total Station point clouds within a rail corridor environment. [USQ Project]


Abstract

At present there is a large array of survey marks and target types used by surveyors when establishing survey control networks for their immediate use and for later use by other spatial science professionals. These targets or marks often only suit the immediate task of the original user who installed them. Subsequent users are then regularly required to place their own particular type of target over the previous survey mark to be able to utilise its attributed geodetic information. This requires the purchase and ongoing use of specialised targets by skilled personnel every time spatial data is to be collected or the geodetic attributes utilised. The costs involved with this continual process could be reduced by the installation of permanent targets which can be utilised by all types of measuring equipment and their associated software. The installation of small, permanently mounted, unobtrusive and inexpensive sphere targets throughout the rail corridor which can be measured from any angle of incidence without the need to be handled by skilled personnel is one potential solution to these problems. The purpose of this research project is to discover what limits the use of small sphere targets when used to georeference Total Station, Photogrammetry and Terrestrial Laser Scan data when captured within a rail corridor environment. These limitations may provide an insight into what improvements to future spatial data measuring technologies will be required to enable the use of a small sphere target control network.

Sphere targets of varying sizes were placed upon overhead wiring masts in two separate locations in the Sydney railway network. The first being a typical straight section of doubletrack railway at Emu Plains, which featured overhead wire masts at approximately 60 metre intervals. The second site was a section of track comprising of a diamond track crossing within the Flemington Maintenance Yard which allowed a better spread of photogrammetry photos to be taken.

A control survey incorporating the sphere targets was established at both locations using Total Station reflectorless measurements. Baseline measurements were also made to specific features within each site which were easily identified in laser scan and photogrammetry point clouds and that are typically of interest in rail corridor surveys. Terrestrial laser scanning (TLS) data and photogrammetry images where then collected throughout each site with the subsequent point clouds being produced using specific software for each mode of data capture. The TLS point cloud was registered and georeferenced using Leica HDS GZT21 4.5 inch Black & White Tilt & Turn Targets which were automatically recognised using Leica Cyclone software. The photogrammetry images were processed and georeferenced using the sphere targets as tie points along with numerous other common tie points identified by Bentley Context Capture and Pix4DMapper software.

Both the registered TLS point cloud and photogrammetry datasets were interrogated to determine the centroid of each sphere and the XYZ coordinate of each point that corresponded with the Total Station baseline points. The resultant data was then analysed to determine the suitability of small sphere targets as site control.


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Item Type: USQ Project
Item Status: Live Archive
Additional Information: Bachelor of Spatial Science (Honours)
Faculty/School / Institute/Centre: Current - Faculty of Health, Engineering and Sciences - School of Civil Engineering and Surveying (1 Jul 2013 -)
Faculty/School / Institute/Centre: Current - Faculty of Health, Engineering and Sciences - School of Civil Engineering and Surveying (1 Jul 2013 -)
Supervisors: Liu, Xiaoye
Date Deposited: 09 Sep 2021 04:58
Last Modified: 05 Oct 2021 05:02
URI: http://eprints.usq.edu.au/id/eprint/40649

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