2017 NOAA/MCP Topobathy Lidar: Blue Hill Bay, ME - Riegl Sensor

Dates of collection: June 29, July 5, 2017

Create custom data files by choosing data area, product type, map projection, file format, datum, etc. A new metadata will be produced to reflect your request using this record as a base.

Bulk download of data files in LAZ format, geographic coordinates, orthometric heights. Note that the vertical datum (hence elevations) of the files here are different than described in this document.

Information on the NOAA Office for Coastal Management (OCM)

The Data Access Viewer (DAV) allows a user to search for and download elevation, imagery, and land cover data for the coastal U.S. and its territories. The data, hosted by the NOAA Office for Coastal Management, can be customized and requested for free download through a checkout interface. An email provides a link to the customized data, while the original data set is available through a link within the viewer.

This graphic displays the footprint for this lidar data set.

Link to data set report.

Link to custom download, from the Data Access Viewer (DAV), the raster Digital Elevation Model (DEM) data that were created from this lidar data set.

Link to custom download the concurrently collected topographic and bathymetric data (collected with the SHOALS 1000-T lidar system).

The airborne raw files from the VQ-820-G sensor are downloaded into RIEGL LMS RiProcess version 1.8.3. The system collects bathymetric LiDAR data at 520 kHz Pulse Repetition Rate for an approximated point density of 8.5 pts/m2 at 400 m altitude (AGL) and 100 kts (speed over ground). 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). The RiProcess process also produced the automated and semi-automated clasification of water surface points to generate a water surface model for refraction correction of all lidar points underwater. Point clouds data was exported to LAS format were additional QC reviews were performed in external tools (Terrascan), including positioning adjustments to overlapping line data. 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 a basic classification produced during the refraction correction process: Emerged and topographic points (1), Noise (7), Submerged Underwater points (40), Derived water surface (42). However, other than this necessary processing classification, the dataset has not been further classified or edited.

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. Ecognition was used to generate a water mask for extracting bathymetric points and identifying water surface and other non-bottom bathymetric points. 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), and class 40 (bathymetric point). Class 40 represents seafloor points. Class 1 on land includes all non-ground points (e.g., vegetation, buildings, powerlines). Class 1 in the water includes all non-bathymetric points (e.g., water surface, water column, floating submerged aquatic vegetation, and docks/piers).

The NOAA Office for Coastal Management (OCM) received 287 las files. The files contained topobathy elevation and intensity measurements in Blue Hill Bay along the coastline of Maine. The data were set to NAD83 2011 UTM Zone 19 North in meters and NAVD88 (Geoid12B) elevations in meters. The data were classified as: 1 -Unclassified, 2 - Ground, 7 - Low Noise, 40 - Bathymetry. OCM processed all classifications of points to the Digital Coast Data Access Viewer (DAV). Classes available on the DAV are: 1, 2, 7, 40.

OCM performed the following processing on the data for Digital Coast storage and provisioning purposes:

1. The LAStools software scripts lasinfo and lasvalidate were run on the las files to check for errors.

2. An internal OCM script was run to check the number of points by classification and by flight ID and the gps and intensity ranges.

3. Internal OCM scripts were run on the las files to convert from orthometric (NAVD88) elevations to ellipsoid elevations using the Geoid 12B model, to convert from NAD83 2011 UTM Zone 19 North in meters to geographic coordinates, to assign the geokeys, to sort the data by gps time and zip the data to database and to http.