Data Management Plan

Fugro was contracted in July 2017 by the State of Maine Department of Marine Resources (SMDMR), Maine Coastal Program (MCP), and the NOAA Office for Coastal Management (OCM) to conduct an Airborne LiDAR Bathymetry (ALB) survey in the vicinity of Blue Hill Bay in Maine, and to deliver fully processed and verified hydrographic survey data.The ALB survey was conducted with the SHOALS-1000T and Riegl VQ-820-G lidar systems in a concurrent acquisition. The SHOALS system, with a high power laser, provided the better probability for deep sounding detections at a reduced point density (about 0.15 pts/m2); whilst the VQ-820-Q provided high density coverage (up to 8.5 pts/m2) but at reduced depth detection.

This metadata record describes the bare earth, 2 meter digital elevation model (DEM) created from the topographic and bathymetric LiDAR elevations generated from data collected with the SHOALS-1000T LiDAR system along Blue Hill Bay on the coastline of Maine. Data were collected by Fugro for NOAA OCM. The SHOALS system is a bathymetric LiDAR sensor for use in coastal mapping and charting activities because the laser's ability to penetrate the water column and detect targets up to 2.5 times the Secchi disk depth. Survey coverage was based on a delimiting polygon provided by NOAA OCM, which envelopes the area between the 0 m contour (NAVD88) down to approximated -10 meters. An additional horizontal buffer of 100 meters from the 0 m contour expanded the survey area coverage to include the adjacent emerged topography. SHOALS data have been processed on Optech SHOALS-GCS and QPS Fledermaus software packages for: auto-processing; calibration, cleaning and editing, validation, basic classification, and exported to LAS format.

In addition to these bare earth Digital Elevation Model (DEM) data, the lidar point data that these DEM data were created from, are also available. These data are available for custom download at the link provided in the URL section of this metadata record.

A topographic and bathymetric reflectance raster are also available. These data are available for download at the link provided in the URL section of this metadata record.

A link to custom download the bare earth DEM that was created from the concurrently collected topographic and bathymetric data (collected with the Riegl VQ-820-G lidar system) is provided in the URL section of this metadata record.

Process Steps:

• The airborne raw files from the SHOALS sensor are downloaded into SHOALS-GCS software version 6.32. The system collects bathymetric LiDAR data at 2.5 kHz Pulse Repetition Rate for an approximated point density of 0.15 pts/m2 at 400 m altitude (AGL) and 100 kts (speed over ground). The SHOALS system also collects RGB imagery at 1 Hz using a Prosilica GX330 digital camera. Aircraft position, velocity, angular and acceleration information collected with an Applanix POS AV 510 v6 equipment were processed using Applanix POSPac v 7.1 software to produce a Smoothed Best Estimate Trajectory (SBET) solution file that is used by RiProcess to produce 3D positions for each LiDAR shot (point clouds). SHOALS-GCS auto-processing routine estimates the water surface and bottom surface points for each laser shot and applied the refraction correction automatically. Upon inspection and QA/QC in Fledermaus software version 7.7, anomalous data were flagged as invalid and bathymetry properly validated. All LiDAR points including bathymetric, topographic, water surface, noise and rejections were exported to LAS format. Elevations referenced to NAVD88 datum were reduced with the application with VDatum v3.6.1. and GEOID12b. Data was exported to LAS format 1.4 for delivery. LAS data has the following classification: Emerged and topographic points (1), Noise and Rejections (7), Bathymetry (40), Derived water surface (42), and Submerged objects (wrecks, rocks, pilings) (43).
• 2018-04-01 00:00:00 - The delivered LAS files were reviewed and processed to classify the point cloud and compute vertical accuracy. A variety of LAStools executables were used to tile the swaths, classify points (noise, ground, and bathymetric points), generate gridded products, and perform the final quantitative accuracy assessment. Global Mapper was used to perform qualitative assessments of the point clouds and gridded products at each step of the classification process. ArcGIS Pro was used to organize and visualize all delivered products and generate web services for team reviews. The final classification includes class 1 (unclassified), class 2 (bare ground), class 7 (low noise), class 40 (bathymetric point), class 42 (derived water surface), and class 43 (submerged objects).
• 2018-04-03 00:00:00 - The SHOALS digital terrain model (DTM) was produced from the classified lidar points using LAStools. Points were filtered to keep only class 2 (ground) and class 40 (bathymetric point). The filtered points were used to construct a triangulated irregular network (TIN) with no triangles being built with edges longer than 10 meters. The TIN was then rasterized onto a 2 meter resolution digital elevation model (DEM).
• 2018-05-09 00:00:00 - The data were in UTM Zone 19 North coordinates and NAVD88 (Geoid12B) elevations in meters. The bare earth raster files were at a 2 meter grid spacing. OCM performed the following processing on the data for Digital Coast storage and provisioning purposes: 1. Copied the files to https.

Data is available online for custom and bulk downloads.