2018-2019 NOAA NGS Topobathy Lidar DEM Hurricane Irma Delivery 1: Miami to Key Largo, FL

The NOAA Hurricane Irma Florida Keys Topobathymetric LiDAR Delivery 1 area data were collected by Quantum Spatial, Inc. (QSI) using three Riegl systems: a Riegl VA880G+, a Riegl VQ880GII, and a Riegl VQ880GH. Delivery 1 acquisition dates spanned from 20181120-20190323 in 23 missions. The final classified LiDAR data were transformed from ellipsoid elevations to Geoid12b elevations and used to create topobathymetric DEMs in ERDAS Imagine (*.img) format with a 1m pixel resolution. Ground (2), bathymetric bottom (40), and submerged objects (43) classified points were used in DEM creation. The Delivery 1 digital elevation model (DEM) dataset consists of a bathymetric void clipped bare earth model and an interpolated bare earth model. The 100 meter buffered project area consists of approximately 1,381,270 acres and stretches from the eastern coast of Miami south and westward to the Marquesas Keys. The NOAA Hurricane Irma Florida Keys Topobathymetric LiDAR Delivery 1 area covers 285,529 acres of the full project boundary. DEM files were compiled in 5000 m x 5000 m tiles and clipped to the project boundary. This Delivery 1 dataset is comprised of 70 5000 m x 5000 m DEM tiles.

1 - unclassified

2 - ground

7 - noise

40 - bathymetric bottom or submerged topography

41 - water surface

43 - submerged feature

45 - water column

46 - overlap bathy bottom - temporally different from a separate lift

71 - unclassified associated with areas of overlap bathy bottom/temporal bathymetric differences

72 - ground associated with areas of overlap bathy bottom/temporal bathymetric differences

81 - water surface associated with areas of overlap bathy bottom/temporal bathymetric differences

85 - water column associated with areas of overlap bathy bottom/temporal bathymetric differences

1 Overlap - edge clip

Please note that classifications 46,71,72,81, and 85 associated with temporal bathymetric differences have only undergone automated classification and have not been manually reviewed.

This data set also includes LiDAR intensity values, number of returns, return number, time, and scan angle. The 100 meter buffered project area consists of approximately 1,381,270 acres and stretches from the eastern coast of Miami south and westward to the Marquesas Keys. The NOAA Hurricane Irma Florida Keys Topobathymetric LiDAR Delivery 1 area covers 285,529 acres of the full project boundary. LAS files were compiled in 500 m x 500 m tiles. This Delivery 1 dataset is comprised of 5,065 - 500 m x 500 m LAS tiles.

This lidar data was required by National Oceanic and Atmospheric Administration (NOAA) and the National Geodetic Survey (NGS), Remote Sensing Division Coastal Mapping Program (CMP) to enable accurate and consistent measurement of the national shoreline. The CMP works to provide a regularly updated and consistent national shoreline to define America's marine territorial limits and manage coastal resources.

The Delivery 1 data includes all lidar returns. An automated grounding classification algorithm was used to determine bare earth and submerged topography point classification. The automated grounding was followed with manual editing. Submerged topography elevations were adjusted to correct for sensor depth bias on a per sensor basis using NOAA provided ground truth data. Intensity values of bathymetric bottom returns were normalized for water depth. Total propagated uncertainty (TPU) values were calculated for the bathymetry data. Classes 2 (ground), 40 (submerged topography), and 43 (submerged object) were used to create the final DEMs. The full workflow used for this project will be documented in the NOAA Hurricane Irma Florida Keys Topobathymetric LiDAR final report, to be provided upon project completion.

Any conclusions drawn from the analysis of this information are not the responsibility of NOAA, the Office for Coastal Management or its partners

Data is available online for bulk or custom downloads

None

Users should be aware that temporal changes may have occurred since this data set was collected and some parts of this data may no longer represent actual surface conditions. Users should not use this data for critical applications without a full awareness of its limitations.

OS Independent

LiDAR horizontal accuracy is a function of Global Navigation Satellite System (GNSS) derived positional error, flying altitude, and INS derived attitude error. The obtained RMSEr value is multiplied by a conversion factor of 1.7308 to yield the horizontal component of the National Standards for Spatial Data Accuracy (NSSDA) reporting standard where a theoretical point will fall within the obtained radius 95 percent of the time. Based on a flying altitude of 400 meters, an IMU error of 0.002 decimal degrees, and a GNSS positional error of 0.015 meters, the RMSEr value for the Delivery 1 area is 0.029. The project specification requires horizontal positions to be accurate to 1.0m(RMSE).

Absolute accuracy was assessed using both Non-Vegetated Vertical Accuracy (NVA) and Vegetated Vertical Accuracy (VVA) survey methods. Survey checkpoints were evenly distributed as feasible throughout the project area. NVA compares known ground check point data that were withheld from the calibration and post-processing of the LiDAR point cloud to the derived gridded bare earth DEM. NVA is a measure of the accuracy of LiDAR point data in open areas with level slope (less than 20°) where the LiDAR system has a high probability of measuring the ground surface and is evaluated at the 95% confidence interval (1.96*RMSE). In the Delivery 1 area, 7 survey checkpoints were used to assess the non-vegetated vertical accuracy. Project specifications require NVA meet 0.196 m accuracy at the 95% confidence interval. Ground check points located in land cover categories other than bare earth, urban, or submerged topography were used to compute the Vegetated Vertical Accuracy (VVA)against the derived gridded bare earth DEM. In the Delivery 1 area, 2 survey checkpoints were used to assess the vegetated vertical accuracy. Project specifications require VVA meet 0.36 m accuracy based on the 95th percentile. Submerged topography points were also tested. In the Delivery 1 area, 118 survey checkpoints were used to assess the submerged topography accuracy. Project specifications require submerged topography shall meet a vertical RMSE of QL2b specified in the Draft National Coastal Mapping strategy 1.0 which is equivalent to 0.30 m RMSE at a depth of 1 m. Please refer to the NOAA Florida Keys Topobathymetric final LiDAR data report for final accuracies, to be provided upon project completion.

The Delivery 1 area dataset Non-Vegetated Vertical Accuracy tested 0.069 m vertical accuracy at 95% confidence level against the derived bare earth DEM in open terrain using 7 ground check points, based on RMSEz (0.035 m) x 1.9600.

The Delivery 1 dataset Vegetated Vertical Accuracy tested 0.113 m vertical accuracy at the 95th percentile against the derived bare earth DEM using 2 landclass points.

The Delivery 1 dataset tested 0.135 m vertical accuracy at 95% confidence level against the derived topobathymetric bare earth DEM using 118 submerged check points, based on RMSEz (0.069 m) x 1.9600. Submerged topography checkpoints usually occur in depths up to 1m.

Data covers the project boundary.

Not applicable

Data is backed up to tape and to cloud storage.