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MAPS, SCALES & PROJECTIONS Map - pictorial representation of the geographic location of selected surface features at a reduced scale - generalized view of an area, usually some portion of the Earth’s surface, as seen from above & greatly reduced in size Cartography - art of mapmaking Map Essentials 1) title - brief summary of the map’s content or purpose 2) date - either date information was gathered or the date of publication or both 3) legend - explanation of the symbols used 4) scale - relationship between length measured on the map & the corresponding distance on the ground 5) direction - normally shown by means of a geographic grid (N-S & E-W) with the addition of a straight arrow pointing northward a) geographic north - true north b) magnetic north - direction which a magnetic compass needle points magnetic declination - angle between true north & magnetic north 6) location - use of a geographic grid system Map Scale - ratio of the distance on a map to that in the real world; expressed as: a) fractional scale (representative fraction, RF) - expresses the ratio with a : or / b) graphic scale (bar scale) - uses a line marked off with graduated distances c) written scale - states the ratio in words Map Scale Sizes - depends on the ratio described; the greater the denominator in a fractional scale, the smaller the scale a) Small - 1:3,168,000 (1 in = 50 mi) b) Medium - 1:125,000 (1 in = 2 mi) c) Large - 1:24,000 (1 in = 2000 ft) Map Projection - reduction of a spherical globe onto a flat surface Globe Properties 1) all meridians are equal in length 2) all meridians converge at the poles 3) all lines of latitude (parallels) are parallel to the equator & to each other 4) parallels decrease in length as the poles are approached 5) meridians & parallels intersect at right angles 6) the scale on the surface of the globe is the same everywhere in all directions The 4 main properties of maps - area, shape, distance, direction - are distorted in different ways & to different degrees by various projections. So the projection must be determined by its intended use