2020 GLOS Underwater Lidar: Lake Huron, MI

Email coastal.info@noaa.gov

In Lake Huron.

Data in NAVD88 (Geoid18) orthometric heights, geographic coordinates for bulk download.

Custom output created with the Digital Coast Data Access Viewer. Projections, datums, file formats, etc, can be changed.

Project report from ASI Group. This metadata was based on the information in the report.

Polygon showing the area of data.

Raw laser scan data collected underwater in Lake Huron.

Multiple locations were tried to test the ROV and laser system. The Detroit River, St. Clair River, and Lake Erie shoreline were found to lack the necessary water clarity. Lake Huron was tried in locations identified using navigation charts. A target was located that appeared to be a large cargo shipwreck. The City of Genoa was a grain freighter that sunk in 1911. The basic structure of the wreck remains on the bed of Lake Huron heavily deteriorated. The ROV was launched at the site and successfully collected laser data of the wreck. Ambient light in the water limited the usable range of the laser, so passes were collected over some areas only.

A review of the data collected during the inspections was completed in the ASI office. The 3D files were converted to point clouds and erroneous noise was removed. The LiDAR files were adjusted in position to best file the sonar data collected of the wreck. The assembly of this report was then completed. The report includes documentation methodology, equipment

descriptions, observations, observation images, and 3D dataset.

Data files are provided of the various areas survey by MBES in meters located in UTM zone 17 as collected and in elevation referenced to NAVD88 and adjusted using Geoid 2018-CONUS. The laser data is provided in LAS format as collected as well as in cleaned XYZ files that have been best-fit positioned to match the MBES data.

Data were delivered to the Great Lakes Observing System (GLOS) and subsequently passed to NOAA Digital Coast for distribution. Both the cleaned text files and the raw LAS files were received. The raw LAS files did not have sufficient information to do the geometric corrections that had been done to the cleaned text files and were not further processed. The cleaned text files were converted to LAS/LAZ format using LAStools txt2las. The points are all tagged as class 2 (ground) as it is presumed that the cleaning step removed non-ground/bathymetry.

This metadata record was created from the report delivered by ASI Group to GLOS. No other metadata was received. GLOS was consulted regarding any accuracy assessments or contractual spatial accuracy requirements. There were none. The accuracy is assumed to be on par with the multi-beam echo sounder data collected at the same time, but that also does not appear to have an accuracy assessment.

Data were converted from UTM zone 17 NAD83(2011) orthometric NAVD88 coordinates to NAD83(2011) ellipsoid heights in geographic coordinates. This allows the distribution through the NOAA Digital Coast Data Access Viewer, which may do further coordinate system changes.