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These contours were extracted from 2 foot contours. The 2 foot contours were generated primarily from a 2014 LiDAR-based DEM dataset acquired by Oregon Metro. Historical LiDAR-based DEM data were used to augment the 2014 DEM as necessary to provide complete coverage for the Tualatin Watershed. The general contour generation process was: 1) Apply evenly weighted 5x5 smoothing to DEM via convolution function 2) Generate contours from smoothed DEM using gdal_contour utility 3) Split contours into 1000 ft segments 4) Remove contours with circumference less than 100 ft 5) Build geometry and attribute indices. |