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<br />. <br /> <br />3. Ground Control. The vertical ground <br />control, contours, spot elevations, and <br />cross-sections shall be based on United States <br />Coast and Godetic Survey (USC&GS) or United <br />States Geological Survey (USGS) monuments <br />related to the National Geodetic Vertical <br />Datum of 1929 (NGVD). The horizontal ground <br />control shall be based on a minimum of 2 <br />USC&GS triangulation stations, or the <br />equivalent. A minimum of third order leveling <br />(closures wi thin ;to. 05 x square root of <br />distance in miles) shall be used to tie <br />temporary bench marks and reference monuments <br />to the National Geodetic Vertical Datum of <br />1929 (NGVD); to determine the elevation of <br />high-water marks; and where needed, to <br />establish vertical control control for aerial <br />photogrammetry. <br /> <br />The ground control surveys shall be supervised <br />by a Land Surveyor licensed in the State of <br />Colorado. All permanent and semi-permanent <br />control markers used for ground control <br />surveys shall be shown and their respective <br />elevations labeled on the work map. <br /> <br />. <br /> <br />4. Contour Interval. The work map contour <br />interval shall be 5 feet or such contour <br />interval showing greater detail. The Board <br />recommends a work map contour interval of 2 <br />feet. <br /> <br />Scale. The work map scale shall be <br />equals 500 feet or such map scale <br />grea ter deta i I. The Board recommends <br />map scale of 1 inch equals 200 feet. <br /> <br />6. Spot elevations. Spot elevations shall be <br />provided at all intersections of the center <br />lines of streets and roads and where needed to <br />supplement the contours. Spot elevations <br />shall also be provided within 50 feet of any <br />building or any small group of buildings that <br />is not wi thin the limits of a city or a town <br />or a platted sUbdivision. <br /> <br />1 inch <br />showing <br />a work <br /> <br />5. <br /> <br />. <br /> <br />7. Cross Sections. The cross-section data <br />shall be obtained by photogrammetric methods <br />at the time of map compilation, from the map <br />contours, or through field surveys. All <br />cross section points derived photogrammetric- <br />ally or from the contours shall meet the <br />accuracy standards in rule 5.A.8. All <br /> <br />-9- <br />