Bare-Earth Surface (Raster Digital Elevation Model) - Using Class 21 (Snow) in DEM

By NGP Standards and Specifications

This revision requirement gives clarity on how to handle the processing of bare-earth digital elevation models (DEMs) in areas with persistent, perennial snowpack.

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Introduction

Areas with persistent snowpack that are not classified as snow and used in the process of creating bare earth DEM’s cause tinning and voids.

Current requirement:

None, this is a new requirement.

Proposed Addition:

Under Bare-Earth Surface (Raster Digital Elevation Model) section:

For datasets that include identifiable perennial snowpack, primarily in high-elevation mountainous regions, the snow classified points will be included in the bare-earth DEM.

A snow-extent polygon feature shall also be included as metadata deliverable and shall be described in the Lidar Mapping Report. Areas of identifiable perennial snowpack with a surface area of 0.8 hectare (ha; 2 acres) or greater (approximately equal to a round pond 100 m in diameter) at the time of collection shall be identified with a snow-extent polygon.