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<br />. <br /> <br />. <br /> <br />. <br /> <br />URITID 5'l7>TES llll'l'IORlL ~p AcaJRAcr STIUImRlS <br /> <br />[A] <br /> <br />Horizontal accuracy--For maps on publication scales larger than 1/20,000, <br />not more than 20 percent of the points tested shall be in error by more <br />than 1/30 inch, measured on the publication scale: for maps on publica- <br />tions scales of 1:20,000 or smaller, 1/50 inch. These limits of accuracy <br />shall apply in all cases to positions of well-defined points only. Well- <br />defined points are those that are easily visible or recO'lerable on the <br />ground, such as the following: m::muments or markers, such as bench <br />marks, property boundary monuments: inteJ:Sections of roads, railroads, <br />etc.: corners of large buildings or structures (or center points of small <br />buildings): etc. In general what is well-defined will also be deteIDIined <br />by what is plott able on the scale of the map within 1/100 inch. Thus <br />while the intersection of two road or property lines meeting at right <br />angles would come within a sensible interpretation, identification of the <br />inteJ:Section of such lines meeting at an acute angle would obviously not <br />be practicable with 1/100 inch. Similarly, features not identifiable <br />upon the ground within close limits are not to be considered as best <br />points within the limits quoted, even though their positions may be <br />scaled closely upon the map. In this class would ccme timber lines, soil <br />boundaries, etc. <br /> <br />[B] Vertical accuracy--As applied to contour maps on all publication scales, <br />vertical accuracy shall be such that not more than 10 percent of the <br />elevations tested shall be in error more than one-half the contour inter- <br />val. In checking elevations taken frem the map, the apparent vertical <br />error may be decreased by assuming a horizontal displacement within the <br />permissible horizontal error for a map of that scale. <br /> <br />[e] The accuracy of any map may be tested by ccmparing the positions of <br />points whose locations or elevations are shown upon it with corresponding <br />positions as dete''lIlined by surveys of a higher accuracy. Tests shall be <br />made by the producing agency, which shall' also determine which of its <br />maps are to be tested, and the extent of such testing. <br /> <br />[D] Published maps meeting these accuracy requirements shall note this fact <br />on their legends, as follows: "This map complies with national map accu- <br />racy standards. II <br /> <br />[El Published maps whose errors exceed those aforestated shall omit frem <br />their legends all mention of standard accuracy. <br /> <br />[F] When a published map is a considerable enlargement of a map drawing (IIBn- <br />uscript) or of a published map, that fact shall be stated in the legend. <br />For example "This map is an enlargement of a 1:20,OOO-scale map drawing," <br />or "This map is an enlargement of a 1:24,000-scale published map." <br /> <br />[G] To facilitate ready interchange and use of basic information for map <br />construction among all federal mapmaking agencies, manuscript maps and <br />published maps, wherever econamically reasonable and consistent with the <br />uses to which the map is to be put, shall conform to latitude and longi- <br />tude boundaries, being 15 minutes of latitude and longitude, or 7.5 <br />minutes, or 3-3/4 minutes in size. <br /> <br />-17- <br />