Description: These topographic contours represent lines of constant elevation on the land portion of the topographic-bathymetric surface model produced by County of Marin and the MarinMap consortium of public agencies. For this feature class, MarinMap member agencies required State Plane projection and contours in even feet, NAVD 1988.On land, only ground-classified returns were selected from each LiDAR point cloud. The topo-bathy surface was defined offshore from surveys including NOAA estuarine grid models, NOAA depth surveys, and CSMP multibeam swaths reduced to gridded models of bathymetry. Where necessary, data were projected (horizontally) to WGS 1984 UTM zone 10 meters, and positioned (vertically) using NOAA VERTCON into NAVD 1988 (Geoid 2003) meters. All input points were converted to multipoint-Z Feature Classes within an ESRI Terrain Dataset, and exported to a 50cm-gridded model surface.For improved contour aesthetics, the 50cm topo-bathy surface was smoothed using a 5x5 mean convolution filter, then resampled to 1m gridding. Even-foot contour elevations were calculated relating US Survey feet to meters by the factor (3937 / 1200), and an AWK script was used to generate a large series of ArcPython ContourList() invocations. The ArcPython produced contour polylines in an ESRI File Geodatabase with a Feature Dataset matching the projection and position of the "tbsm50cm_20121130d" surface model. When completed, the contour polylines were merged then projected by exporting into a new File Geodatabase with a Feature Dataset matching the MarinMap product requirements. Finally, the product was uploaded to the MarinMap ArcSDE repository as "dtm_ELEVATION_CONTOUR_2011_NAVD88".For GIS use, the attribute "USft_elev" holds an integer value of the contour line's elevation in US Survey Feet. For more efficient display, there are index attributes that flag whether a given line's elevation is a multiple of [4, 10, 20, 50, 100, 250, 500] feet; these index attributes are intended for use in definition queries to reduce the density of displayed contours and permit different symbology (typically bolder) for every fifth contour as an index line.