2019 NOAA Lidar DEM: Padilla Bay NERR and Skagit River Delta, WA

This dataset is a digital elevation model (DEM) derived from LiDAR (Light Detection and Ranging) point cloud data of the coastal tidal parts of Skagit and Snohomish Counties in WA State. The National Oceanic and Atmospheric Administration’s Office for Coastal Management contracted with Tetra Tech to acquire and process airborne LiDAR over an area of about 186 square miles. Data was to be acquired within a 2 hour window of low tide. Deliverables included classified LiDAR point clouds, breaklines and digital elevation models (DEM). LiDAR data was acquired on 13 and 14 of August 2019. The coastal area was covered in one flight on 8/14 while the inland area was covered on 8/13. The coastal flight took place on 8/14 with a tide window between -0.7 and +0.5 foot. For the airborne LiDAR flight Tetra Tech subcontracted with Eagle Mapping. The data was acquired with a Riegl LMS VQ780i sensor. A ground control survey was conducted to collect calibration points and check points. For the aerial acquisition Tetra Tech contracted with Eagle Mapping. For the ground survey, Tetra Tech contracted with Compass Data. The LiDAR data and derivative products were to be based on the USGS LiDAR Base Specifications. The coordinate reference system is UTM Zone 10N meters, NAD83(2011). The vertical datum is NAVD88 with Geoid12B.

The purpose of this data is to support coastal resource managers, watershed managers, and various stakeholders in their decision making processes.

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be aware that temporal changes may have occurred since this data set was collected and some parts of this data may no longer represent actual surface conditions.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.

Version 6.2 (Build 9200) ; Esri ArcGIS 10.6.0.8321

The data has been collected to meet or exceed a horizontal accuracy of <= 1m.

Ground control survey was conducted by CompassData. CompassData collected 31 points in non-vegetated areas (NVA) and 21 points in vegetated areas (VVA). 7 of the NVA points were provide to Eagle Mapping for point cloud calibration. These points were not used in the absolute accuracy testing. Four control reports were prepared to document the absolute accuracy of the ground classified LiDAR data and the derived digital elevation models. The absolute accuracy was tested for the NVA assessment of the classified ground points, VVA assessment of the classified ground points, NVA assessment of the DEM, and VVA assessment of the DEM. Three VVA points were removed because they were located on slopes, one VVA point was removed automatically as being an outlier. The vertical accuracy requirements for this project for the DEM data were: NVA RMSE < 0.1 m and NVA 95% error < 0.196m and VVA 95% error < 0.294m.

The NVA RMSEz = 0.044 m and was calculated using 25 vertical checkpoints on flat hard surfaces in non vegetated open terrain.

The NVA error at the 95 % level z = 0.064 and was calculated using 25 vertical checkpoints on flat hard surfaces in non vegetated open terrain.

The VVA RMSEz = 0.139 m and was calculated using 18 vertical checkpoints on flat hard surfaces in non vegetated open terrain.

The VVA error at the 95% level = 0.223 m and was calculated using 18 vertical checkpoints on flat hard surfaces in non vegetated open terrain.

The Area of interest covers approximately 186 square miles and has been extended by a buffer of 100 meters. The classified LAS files cover the entire area and include all points. No points inside the area were removed. All swaths were inspected to ensure that there are no data gaps except over water bodies.

The LiDAR data and derived products cover the 186 square mile area of interest (AOI) plus a 100 meter buffer. The classified LiDAR point cloud and the derived breaklines hav been clipped to the buffered AOI. The derived digital elevation model (DEM) has a define NoDataValue outside of the buffered AOI. All data is delivered in 82 tiles. There are no data gaps or mismatches between tiles.