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Introduction
Spatial metadata for the 3D Elevation Program (3DEP) is available by work unit in the Work Unit Extent Spatial Metadata (WESM) GeoPackage. The WESM contains information about what Lidar Point Cloud (LPC) and source DEMs (also known as Original Product Resolution (OPR) DEMs) work units have been processed and made available to the public. It includes metadata about elevation projects, including quality level, data acquisition dates, and links to project-level metadata. A new WESM is written daily as more elevation projects are processed and published. This data dictionary defines and describes the attributes used in the WESM, including allowed or valid values where appropriate.
The attributes used in the WESM can be grouped into two sets: general attributes that describe basic metadata that applies generally to all work units and the product status codes that include metadata explaining how a given work unit relates to the 3DEP product specifications.
The product status codes in the WESM indicate if and how work units and projects meet or do not meet associated product specifications. The spatial metadata in the WESM applies to four products: the Lidar Point Cloud (LPC), the Source Digital Elevation Model (source DEM), the one-meter DEM (1-m), and the seamless DEM products (seamless). The product status codes include both a category, indicating if a work unit meets or does not meet a specification, and a reason code which gives a brief explanation of why the category was assigned to the work unit. The reason codes relate directly to requirements in the associated product specification. For example, if voids in a lidar collection are unavoidable and are discussed in advance and delineated, for the Lidar Point Cloud product, the work unit would be assigned a category code of "Meets with variance" and a reason code of "Data voids - delineated". The codes for the other products often depend on the codes for the LPC, source DEM, and 1-m DEM, respectively. For the example cited, the source DEM would receive a category of “Meets with variance” and a reason code of “LPC Meets with variance”.
The WESM Data Dictionary is available through the links below, which define the spatial metadata attributes.
