Laserfiche WebLink
<br />. <br /> <br />. <br /> <br />National Map Scale Accuracy <br /> <br />Horizontal <br />for 90% of features <br /> <br />for <br /> <br /> <br />1"=2000' <br />1"=1000' <br />1"= 500' <br />1"= 400' <br />1"= 200' <br />1"= 100' <br /> <br />50' <br />25 <br />12 <br />10 <br />5 <br />2.5 <br /> <br />100' <br />50' <br />25 <br />20 <br />10 <br />5 <br /> <br />Valley slopes for drainages having a large enough drainage area <br />to need regulation in Colorado vary from about 1.1 ft. per 100 feet <br />(%) to about.3 feet per 100 feet. Examples in the Denver area are: <br /> <br />Valley slope (%) <br /> <br />Stream' reach <br /> <br />0.25 <br />0.5 <br />1.0 <br />1.2 <br /> <br />South Platte River through Denver <br />Bear Creek at Wadsworth Boulevard <br />Weir Gulch at Wadsworth Boulevard <br />Little Dry Creek at Wadsworth Boulevard <br />(north of Arvada) <br />Lena Gulch at W. 6th Ave, <br /> <br />3.0 <br /> <br />Assume that 0.5 foot vertical tolerance is permissible in locating <br />a point on the ground and that 0.2' of this is taken up in interpre- <br />tations and scaling distances from the map and in the field surveys <br />for establishing of the elevation. This leaves a permissible <br />horizontal error on the ground related to a vertical tolerance of <br />0.3' . <br /> <br />Required horizontal tolerance along the valley for a given vertical <br />tolerance is relatE~d to the valley slope. For example, a 0.3 vertical <br />tolerance would permit the following horizontal tolerance. <br /> <br />permissible horizontal tolerance <br />related to 0.3 foot vertical tolerance <br /> <br />Valley slope % <br /> <br />0.1 <br />0.25 <br />0.5 <br />1.0 <br />1.5 <br />2.0 <br />3.0 <br />The smallest scale map meeting <br />that would be satisfactory assuming <br />then becomes. <br /> <br />300' <br />120' <br />60' <br />30' <br />20' <br />IS' <br />10' <br />national map accuracy standards <br />a 0.3 foot vertical tolerance <br /> <br />-2- <br />