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o Class 17 — Bridge Decks <br />o Class 18 — High Noise (high, manually identified, if necessary) <br />o Class 20 — Ignored Ground (break line proximity) <br />o Class 21 — Snow (where reliably identified) <br />o Class 22 — Temporal Exclusion (typically non -favored data in <br />intertidal zones) <br />Class 1 will be used for feature points that are not in Classes 2, 7, 8, 9, 10, 17 or 18. These <br />typically represent returns from man-made structures, vegetation etc. <br />Class 7 will be used for artifacts that do not represent the ground, manmade structures or <br />vegetation. Typically, these are extraneous points that are below the surface not representing <br />any true feature. <br />Class 18 will be used for artifacts that do not represent the ground, manmade structures or <br />vegetation. Typically, these are extraneous points that are well above the surface not <br />representing any true feature. No points will be deleted from the LAS file. <br />Hydro -flattened Bare Earth Surface (Raster DEM) <br />• Cell Size no greater than 1.5 U.S. Survey Feet for QL1, and no less than the design Aggregate <br />Nominal Pulse Spacing (ANPS). <br />• Delivered in industry -standard, GIS-compatible, 32-bit floating point raster format in <br />Geographic Tag Image File Format (GeoTiff )format. <br />• Geo-reference information will be included in raster file. <br />• Tiled delivery, without overlap or gaps. <br />• Tiles will be suitable for creating seamless data mosaics. <br />• DEM tiles will show no edge artifacts or mismatches. <br />• Void areas (i.e., areas outside the project boundary but within the tiling scheme) will be coded <br />using a unique "NODATA" value. This value will be identified in the appropriate location <br />within the file header. <br />• A report on the assessed absolute vertical accuracy (NVA and VVA) of the bare -earth surface <br />in accordance with the guidelines set forth in the "Positional Accuracy Standards for Digital <br />Geospatial Data" (American Society for Photogrammetry and Remote Sensing, 2014). <br />Absolute vertical accuracy requirements using the ASPRS methodology for the bare -earth <br />DEM are listed in "Absolute vertical accuracy for digital elevation models, Quality Level 0— <br />Quality Level 3 (table 5). <br />• Depressions (sinks), natural or man-made, are not to be filled (as in hydro -conditioning and <br />hydro -enforcement). <br />• Water Bodies (ponds and lakes), wide streams and rivers ("double -line"), and other non -tidal <br />water bodies as defined in Section III are to be hydro -flattened within the DEM. <br />• Bridges (as defined in the USGS Lidar Base Specification V2.0) will be removed from the <br />DEM. Roads or other travel ways over culverts will remain intact on the surface. <br />• The bare earth surface below a bridge will be a continuous logical interpolation of the apparent <br />non-hydrographic terrain lateral to the bridge deck. Where abutments are clearly visible, the <br />bare earth interpolation will begin at the junction of the bridge deck and approach structure. <br />Where this junction is not clear, NV5G, Inc. will use their best judgment to delineate the <br />separation of below -bridge terrain from elevated bridge surface. <br />• No geometric change will be made to the originally computed Lidar points. Bare -earth Lidar <br />points that are near break lines will be classified as Ignored Ground (class value equal to 10) <br />and will be excluded from the DEM generation process. This process prevents unnatural <br />Page 14 <br />