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First results from the new Topo-Bathymetric lidar look great

First data processed from NSCC-AGRG’s Chiroptera II topo-bathymetric lidar sensor

The figure above represents some of the first data processed from NSCC-AGRG’s Chiroptera II topo-bathymetric lidar sensor. Map (A) represents the shaded relief of a Digital Surface Model (DSM) acquired with a traditional topo lidar sensor in 2011 for Cape John, NS. Notice how there is only elevation data collected on the land and not for the submerged terrain. In contrast map (B) represents the shaded relief of a DSM acquired with the new topo-bathy lidar sensor in Sept. 2014. The lidar penetrated the water to 6 m and reveals a series of reefs that relate to the bedrock geology and in some locations covered with a layer of sand. The rocks are deformed as can be seem from the changes in orientation of the reefs, especially near the point where folding is evident. These data are extremely useful for highlighting potential navigation hazards in the near shore. This new technology provides a much more complete and precise picture of the near shore compared to the existing navigation chart from the Canadian Hydrographic Service (Map C). Map D represents the lidar based colour shaded relief DSM where yellow and green tones are submerged topography and brown tones represent land features.

Introduction

The requirement for accurate and detailed information along Canada’s coastal zone is imperative in order to protect existing and plan for future infrastructure, and to make sound decisions with regard to activities that support economic development. Recently the Applied Geomatics Research Group (AGRG) at the Nova Scotia Community College (NSCC) acquired a topographic-bathymetric (topo-bathy) lidar sensor and high resolution aerial camera that is capable of surveying the land elevations and the submerged coastal topography. The ability of an airborne sensor to accurately survey the near shore bathymetry (submerged elevation) offers an opportunity to produce detailed information across the land-sea boundary in an area that has traditionally not been mapped because of the expense and limitations of traditional mapping technologies (air photos on land and boats and echo sounders on the water).

The lidar sensor is a Chiroptera II integrated topographic bathymetric lidar sensor equipped with a 60 megapixel multispectral camera. The system incorporates a 1064 nm near infrared laser for ground returns and sea surface and a green 532 nm laser for bathymetric returns. The lasers scan in an elliptical pattern, which enables coverage from many different angles, on vertical faces, causes less shadow effects in the data, and is less sensitive to wave interaction. The bathymetric laser is limited by depth and clarity, and has a depth penetration rating of 1.5 x the Secchi depth (a measure of turbidity or water clarity using a black and white disk). The Leica RCD30 camera collects co-aligned RGB+IR motion compensated photographs which can be mosaicked into a single image in post-processing, or analyzed frame by frame for maximum information extraction. AGRG-NSCC does not own an aircraft, only the sensor. AGRG partnered with Leading Edge Geomatics to assist in the operations of the survey and arranging the aircraft.

The lidar surveys were conducted in study areas in Nova Scotia and New Brunswick during the week of Sept 22-29th. Projects were initiated between NSCC-AGRG and a variety of clients including NSRERC, private sector companies, and both federal and provincial government departments. Stayed tuned as more results become available from the different projects.

Mark your calendar, Wed. March 3rd, AGRG-NSCC will be hosting a “Workshop on the Results of our Topo-Bathy lidar Survey Campaign 2014” at the Delta Halifax. Admission to the event is free and is meant to stimulate industry and researchers on the benefits of this new technology. This workshop follows on the successful workshop with over 90 participants was held in Feb. 2014 where the technology and planned research was presented. For more information about applied research projects utilizing this technology or the workshop in March contact. Dr. Tim Webster, tim [dot] webster [at] nscc [dot] ca.

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