Consolidated Standardized Survey-Grade Checkpoints 3DEP 2010 to 2017 - ScienceBase-Catalog

The 3D Elevation Program (3DEP) is managed by the U.S. Geological Survey (USGS) National Geospatial Program to respond to growing needs for high-quality topographic data and for a wide range of other three-dimensional (3D) representations of the Nation's natural and constructed features. 3DEP informs critical decisions that are made across our Nation every day that depend on elevation data, ranging from immediate safety of life, property, and environment to long term planning for infrastructure projects. Lidar, an airborne laser detection technology for mapping features on the ground, is being collected nationwide, while Interferometric Synthetic Aperture Radar (IfSAR) is being collected over Alaska. Assessing the accuracy of the lidar point cloud data collected for 3DEP is defined in the Lidar Base Specification (https://www.usgs.gov/ngp-standards-and-specifications/lidar-base-specification-online). The vertical accuracy of the lidar and IfSAR data and the derived Digital Elevation Models (DEMs) is the most scrutinized accuracy metric. 3DEP data are assessed and reported in accordance with the American Society of Photogrammetry and Remote Sensing (ASPRS) Positional Accuracy Standards for Digital Geospatial Data. Vegetated vertical accuracy (VVA) and non-vegetated vertical accuracy (NVA) are assessed for absolute vertical accuracy compared to survey-grade checkpoints collected with Global Navigation Satellite System (GNSS) receivers by professional land surveyors. These checkpoints are published with 3DEP projects (https://rockyweb.usgs.gov/vdelivery/Datasets/Staged/Elevation/metadata/) and represent tens of millions of dollars of high accuracy data that can be used to assess both 3DEP and other endeavors such as the Seamless 1-m DEM that the National Geospatial Directorate is producing to support the USGS 3D National Topography Model. However, these checkpoints were not standardized until Lidar Base Specification 2022 rev. A. All checkpoints prior to this revision were delivered by contractors in XML, PDFs, excel spreadsheets, CSVs, shapefiles, and geodatabase feature classes depending on the preference of the lidar contractors and 3DEP partners. In 2021, the National Geospatial Technical Operations Center (NGTOC) consolidated the checkpoints in the 3DEP and older lidar/IfSAR data holdings gathered between 2010-2017 to support research for and the eventual publication of a journal article called “The Accuracy and Consistency of 3D Elevation Program Data: A Systematic Analysis” (https://doi.org/10.3390/rs14040940). In 2024, NGTOC enriched and standardized the points used in that paper to match the current survey point delivery schema. This included re-projecting the data horizontally to North American Datum of 1983 (NAD83) (2011) geographic, deleting duplicate points, identifying the point type as NVA or VVA, identifying matching work unit and project ID numbers within the Work Unit Extent Spatial Metadata, verifying the correct geoid models, using National Oceanic and Atmospheric Administration’s (NOAA) National Geodetic Survey (NGS) VDatum tool to update the Z elevation values in the conterminous United States (CONUS) and Puerto Rico into meters and GEOID18 and everything in Hawaii and Alaska into meters and GEOID12B, determining the collection date and the publication date, and finding the URL to the source information where possible. This is the first version of the 3DEP checkpoints database which includes 41,958 survey-grade points from 205 lidar and IfSAR projects covering 710 published work units. NGTOC will update this database with additional checkpoints in 2025.

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