Using Multiple Survey Technologies in a Marine Environment
At SurvTech, we pride ourselves on using the latest survey technology to find new and groundbreaking solutions for our clients. Recently, we had the opportunity to combine several of the survey technologies that we have been using for years to accurately map three structures at a client’s berth. A client needed the three structures accurately located and checked for plumbness to design purposes. SurvTech utilized a combination of RTK (real time kinematic) GNSS, mobile LiDAR from a marine survey vessel, and metrology.
To perform an accurate survey the structures would have to be scanned from multiple angles. Horizontal and vertical control was established with a Leica Absolute Tracker AT-403 which can produce horizontal and vertical precision of 1/10,000th of an inch. Although, on this project those accuracies were not required. The control was georeferenced utilizing RTK GNSS with Carlson Brx6+.
To obtain a complete (dense) 3d dataset and have redundancy for data quality checks, the mobile LiDAR was performed in multiple passes with the survey vessel running in opposing directions. SurvTech equipped our 25-foot survey vessel with our LiDAR USA “Snoopy” mobile LiDAR unit, which has served us well on many projects. This same system is routinely mounted on our fleet of UAV’s, surveying trucks, ATVs, and amphibious vehicles. Our Leica AT 403 was also used as an additional check of our LiDAR point data accuracy. Precise survey measurements were taken by positioning the tracker on one of the concrete structures, and measuring specific points on the structures. Even in outdoor conditions the tracker can obtain horizontal and vertical measurements of higher accuracy than any survey total station or level. The point cloud data was processed with TerraSolid, and the metrology data was processed with Spatial Analyzer. The two data sets were then compared in Microstation, AutoCAD, and Spatial Analyzer to ensure the accuracy of the results. This was our first experience using the absolute tracker in a marine environment, and we were pleased with its visibility and accuracy under outdoor conditions.
The dataset was delivered to the clients for design of the berth improvements. This project demonstrates SurvTech’s ability to acquire and manipulate numerous geospatial datasets simultaneously and produce a usable product for the client. Although we did NOT collect any type of bathymetry or sonar data while performing the survey, SurvTech has the capabilities to collect single beam, multi beam, side scan or magnetometer data simultaneously and added subaqueous information to the 3D dataset. SurvTech’s geospatial team ensures that geospatial data is tailored specifically to meet each of client’s needs, under varying site conditions, and in the most efficient format for them to work with.