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Producing 3D Georeferenced Data Above and Below the Waterline

Published Date

Measutronics Corporation is a full service provider of marine positioning and guidance systems for vessel navigation, precise piling and structure placement, dredging operations, local and remote vessel tracking and monitoring, excavator operations and hydrographic, bathymetric and coastal surveying.  They specialize in the use, installation, training and consultation of select Trimble GPS equipment and software as well as a variety of other marine positioning products.

Measutronics partners with several industry leading manufacturers, including Applanix, a Trimble Company.  “Applanix brings a quality product to the table while we bring the experience and ability to integrate with other systems,” said Lou Nash, President of Measutronics.


THE CHALLENGE: 

Create a model of the bridge pilings in Garrison Channel, Tampa, Florida

The Garrison Channel is one of several channels for boat traffic in and around the Port of Tampa.  It is located by Channelside on the East leading to Ybor Channel and Sparkman Channel, and by the Tampa Convention Center on the west leading to Hillsborough River.  As a proof-of-concept, the objective here was to produce detailed, georeferenced, and integrated multibeam (below waterline data) and LiDAR (above waterline) data of the bridge and the bridge pilings that cross the Garrison Channel.   The integration of both data types would yield a complete 3-D model of the bridge and bridge pilings. This project represented one of the first deployments of LANDMark Marine, and would provide an excellent indication of its capabilities in a typical port environment.


THE APPLANIX SOLUTION: LANDMark Marine

Mapping the geography, seabed and man-made structures in coastal waters means conducting highly detailed mapping exercises onboard a dynamic marine vessel, frequently in areas where bridges and other shoreline structures – the very items to be surveyed – make the GPS environment extremely difficult. Essential to the solution was the Applanix POS MV™ (Position and Orientation System for Marine Vessels) which provided accurate vessel attitude, heading, heave, position, and velocity data of the survey vessel, allowing georeferencing and motion compensation of  all the data obtained by the R2Sonic 2024 multibeam sonar and LANDMark Marine LiDAR system onboard the vessel.

Applanix’ unique POSPac MMS (Mobile Mapping System) aided inertial software package was used to produce the most robust and accurate georeferencing and motion compensation solution possible.  POSPac MMS is powerful post-mission software that processes the data from the POS MV to provide Direct Georeferencing for the multibeam and LiDAR data.  Optimized for the specific requirements of marine surveying, POSPac MMS is a complete post-processing toolbox, delivering a streamlined, field-to-office workflow for maximum accuracy and efficiency in Direct Georeferencing.  In a simple yet powerful workflow, GPS and inertial observables logged by POS MV during the survey, together with observables from a network of GPS reference stations, were post-processed by POSPac MMS to create the most robust and accurate solution possible – the  Smoothed Best Estimate of Trajectory (SBET).  To enable centimetric positioning accuracy even when the nearest GPS reference station is 80 or more kilometres distant, POSPac MMS implements SmartBase, a post processed Virtual Reference Station. The SmartBase, plus GPS and inertial data from POS MV are combined in a tightly coupled process, producing the optimal position and orientation solution. By translating this solution to the appropriate locations on the vessel, the SBET solution was then used to georeference both the multibeam and LiDAR observations. The result is a seamless point cloud, both above and below the waterline. 


THE RESULT:

The Applanix Solution provided a reliable, safe and efficient method for obtaining both short and long-range spatial data in a typical port environment. The results achieved are best demonstrated by reviewing the merged multibeam & LiDAR point cloud data (see Figure 1).  The data sets, collected from 2 independent sensors, when merged together deliver a single coherent image. 

By operating LiDAR and sonar devices simultaneously, only one data gathering mission was required, saving time and eliminating the requirement to deploy personnel in potentially hazardous areas onshore..