EQUILATERAL—A polygon with sides of equallength.ERROR—The difference between an observed orcomputed value of a quantity and the true valueof the quantity. Errors are of two classifications:accidental errors and systematic errors.ERROR OF CLOSURE—The amount by whichthe value of a quantity obtained by surveyingoperations fails to agree with another value of thesame quantity held fixed from earlierdeterminations or with a theoretical value of thequantity.EXPONENT—A small number or symbol placedabove and to the right of a mathematical quantityto indicate the number of times the quantityis to be multiplied by itself; for example,EXTENSION LINES—Thin, unbroken lines usedto extend dimensions beyond the outline of a viewso they can be more easily read.FINITE DISTANCE—A defining measurabledistance.FIRST ANGLE PROJECTION—Multiviewprojection commonly used in Europe in which thetop view is below the front view and the right sideof the object, as shown in the front view, is towardthe left side view of the object.FORESHORTENING—The reduction in lengthof receding lines in an oblique projection thatallows the object to appear to be optically correct.FORESIGHT— 1. A sight on a new survey point,made in connection with its position determina-tion; or a sight on a previously established pointto close a circuit. 2. In leveling, a foresight(FS) is the rod reading on a rod held on apoint whose elevation is being determined. (SeeBACKSIGHT.)FORMAT—The systematic arrangement ofdrawing sheet spaceto standardize the locationof required information.FRACTION—A division indicated by placing thedividend (numerator) over the divisor (denomi-nator) wit h a line between them.Proper Fraction: 3/4Improper Fraction: 3/2 = 1 1/2Mixed Fraction: 1 7/8FRENCH CURVE—Instrument used to drawsmooth irregular curves.FREEHAND DRAFTING—Any drawing inwhich the pen or pencil is guided solely by hand.FRUSTUM OF A CONE—The portion of a cone-shaped solid next to the base that is formed bycutting off the upper part by a plane parallel tothe base.FRUSTUM OF A PYRAMID—The portion ofa pyramid-shaped solid next to the base that isformed by cutting off the top by a plane parallelto the base.FULL SECTION—A sectional view that passesentirely through the object.GEODETIC DATUM—Datum that forms thebasis for the computation of horizontal-controlsurveys in geodetic surveying. It consists of fivequantities: the latitude and the longitude of aninitial point, the azimuth of a line from this point,and two constants necessary to define theterrestrial spheroid.GEOMETRY—That branch of mathematics thatinvestigates the relations, properties, and measure-ment of solids, surfaces, lines, and angles; it alsodeals with the theory of space and of figures inspace.GRADE (GRADIENT)—The rate of rise and fallor slope of a line; generally expressed in percentor as a ratio.GRAPH PAPER—Gridded paper in a variety ofscales and patterns used for plotting, sketching,and drawing.GRID—A network composed of two sets ofequidistant parallel lines intersecting at rightangles.GRID COORDINATES—The numbers andletters of a coordinate system that designate apoint on a grid.GUARD STAKE—A stake driven near a hub,usually sloped with the top of the guard stake overthe hub. The guard stake protects, and itsmarkings identify, the hub.AI-6
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