2016 - 2017 PSLC Lidar DEM: King County, WA

This metadata record was created by the NOAA Office for Coastal Management (OCM). Information from the PSLC King County 2016 - 2017 Lidar Final Technical Data Report, dated June 23, 2017, were used to populate this record.

In February 2016, Quantum Spatial (QSI) was contracted by the Puget Sound LiDAR Consortium (PSLC) in association with the Kitsap County Department of Emergency Management to collect Light Detection and Ranging (LiDAR) data in early 2016 for the PSLC King County sites in Washington. Data were collected to aid PSLC in assessing the topographic and geophysical properties of the study area to support a variety of tasks including municipal planning, change detection and geomorphic mapping, and hazard mitigation. These data were collected between February 24, 2016 and May 25, 2017.

OCM downloaded 5 tif files from the PSLC ftp site (http://pugetsoundlidar.org/lidardata/restricted/las/pslc2016/KingCounty, Delivery 1, 2, 3, 4 Block 1 and 4 Block 2) and processed the data to the Data Access Viewer (DAV) and https. During processing, it was noted that many of the water bodies/areas are depicted as ground. The bare earth rasters are at a 3 ft grid spacing.

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.

Data were collected to aid PSLC in assessing the topographic and geophysical properties of the study area to support a variety of tasks including municipal planning, change detection and geomorphic mapping, and hazard mitigation.

Users should not use these data for critical applications without a full awareness of its limitations. Any conclusions drawn from the analysis of this information are not the responsibility of PSLC, NOAA, the Office for Coastal Management or its partners.

Data is available online for bulk and custom downloads.

None

In some areas of heavy vegetation or forest cover, there may be relatively few ground points in the LiDAR data. TINing the points produces large triangles and hence the elevations may be less accurate within such areas. Elevation values for open water surfaces should be considered approximate due to the increase of laser noise seen over water, frequent lack of returns, and the overall dynamic nature of water.

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.

Waypoint Interial Explorer v.8.6; Leica Cloudpro v. 1.2.2; TerraScan v.17; TerraMatch v.17; TerraModeler v.17; ArcMap v.10.2.2; Las Monkey; Las Product Creator

Absolute accuracy was assessed using Non-Vegetated Vertical Accuracy (NVA) reporting designed to meet guidelines presented in the FGDC National Standard for Spatial Data Accuracy3. NVA compares known ground quality assurance point data collected on open, bare earth surfaces with level slope (<20 degrees) to the triangulated surface generated by the LiDAR points. NVA is a measure of the accuracy of LiDAR point data in open areas where the LiDAR system has a high probability of measuring the ground surface and is evaluated at the 95% confidence interval (1.96 * RMSE), The absolute accuracy statistics for the individual King County deliveries are documented in the Final Technical Report, Appendix B (Table 14 and Table 15, Figure 18 through Figure 27).

The mean and standard deviation (sigma σ) of divergence of the ground surface model from quality assurance point coordinates are also considered during accuracy assessment. These statistics assume the error for x, y and z is normally distributed, and therefore the skew and kurtosis of distributions are also considered when evaluating error statistics. For the King County survey area, 217 quality assurance points were withheld in total resulting in a non-vegetated vertical accuracy of 0.204 feet (0.062 meters) or RMSE of 3.2 cm.

LiDAR data has been collected and processed for all areas within the project study area.

Shaded relief images have been visually inspected for data errors such as pits, border artifacts, and shifting. LiDAR flight lines have been examined to ensure consistent elevation values across overlapping flight lines.