Description: The hillshade model shows how the ground surface would be lit up by a light source if there were no obstructions (buildings, trees, etc.) across the City of Bothell, WA and surrounding area. This model highlights topographic relief (hillslopes) and is typically used for cartographic purposes as a basemap. This hillshade model was developed from bare earth (ground) elevation points in lidar data collected between April 1 and April 15, 2021.City of Bothell staff developed the hillshade model by first creating a 1-foot resolution bare earth elevation raster (also known as a Digital Elevation Model, or DEM) from the lidar LAS data (point cloud) provided by the contractor. The digital elevation model attempts to show the ground elevations without any surface features such as buildings or trees. Where surface features obstruct lidar pulses from reaching the ground (e.g. under a building), the DEM approximates the ground elevation from the surrounding area. Hydroflattening on large bodies of water (e.g. the Sammamish River) was also applied using breaklines provided by the contractor, supplemented by large water bodies (classified as "Lakes") in Bothell's own Water Bodies polygon dataset. A hillshade raster was then created from this DEM raster with a Z factor (vertical exaggeration) of 3 to accentuate hillslopes and topographic relief. ArcGIS Desktop 10.8.1 (ArcMap) was used for all steps by City of Bothell staff.Metadata from NV5 Geospatial (contractor):The purpose of the lidar data was to produce a high accuracy 3D dataset that meets all necessary standards laid out by the 3D Elevation Program and the WA King County contract. The lidar point cloud data were used to create classified lidar LAS files, intensity images, hydro-flattened DEMs, highest hit DSMs, and 3D breaklines of rivers and lakes within the study area.Product: Classified LAS 1.4 files, formatted to 1294 individual 4500usft x 4500usft tiles covering the WA King County project area.Geographic Extent: This dataset and derived products encompass an area covering approximately 563,405 acres of Western Washington.Dataset Description: The WA King County Lidar project called for the planning, acquisition, and processing of lidar data collected to Quality Level 1 (QL1) standards for this portion of the project area. Project specifications are based on the U.S. Geological Survey National Geospatial Program LIDAR Base Specification, Version 2.1. The data was developed based on the NAD83 2011 horizontal datum and the NAVD88 Geoid 18 vertical datum. Data was projected in Washington State Plane North, U.S. survey feet. Lidar data was delivered as calibrated and classified LAS 1.4 files. Non-Vegetated Vertical Accuracy (NVA) was assessed using 0 check points located on bare earth in clear, unobstructed areas. Vegetated Vertical Accuracy (VVA) was assessed using 0 check points in Tall Grass, Forest, and Shrub landcover types. Single swath nominal pulse spacing (NPS) was designed to be 0.50 m at nadir. Aggregate Nominal Pulse Spacing (ANPS) was calculated to be 0.35 m using all valid first return points. Derived products include: Intensity Imagery, Hydro-flattened Bare Earth Digital Elevation Models (DEMs), Highest Hit Digital Surface Models (DSMs), and 3D waters edge breaklines.Ground Condition: Ground condition was free of snow and acquisition occured free of smoke, fog and cloud cover.Ground Control Points were acquired and calibrated by NV5 Geospatial.All lidar data acquisition, calibration, and follow-on processing were completed by NV5 Geospatial.Users should be aware that temporal changes may have occurred since this dataset was collected and that some parts of these data may no longer represent actual surface conditions. Users should not use these data for critical applications without a full awareness of its limitations. Acknowledgment of the U.S. Geological Survey would be appreciated for products derived from these data.
Copyright Text: U.S. Geological Survey, Quantum Spatial, Inc., NV5 Geospatial
Acknowledgment of the U.S. Geological Survey would be appreciated for products derived from these data.
Ground Control Points were acquired and calibrated by NV5 Geospatial.
All lidar data acquisition, calibration, and follow-on processing were completed by NV5 Geospatial.
Created and maintained by:
City of Bothell | Washington State
Information Services Department | GIS Services Section
18415 101st Ave NE | Bothell, WA 98011
P: 425.806.6170
E: GISRequest@bothellwa.gov