A map-interpretation tool has been developed to quickly and accurately aid in the solution of various problems concerning line of sight between or beyond two points, on, below, or above the earth's surface. The apparatus consists of a transparent plastic base inscribed with a series of parallel horizontal lines to represent elevations on a map; a movable vertical line to locate horizontal distances on a map; and another movable line which pivots at an angle to simulate a line of sight between two points. The device eliminates the time-consuming process of drawing earth profiles. This is done by positioning the device on a contour map, establishing the line of sight between the two points, and constructing on the device an imaginary profile. Many applications of the basic principle of the device can be made and a variety of problems solved with it.
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