Identifier: topographicmapss00finc (find matches)
Title: Topographic maps and sketch mapping
Year: 1920 (1920s)
Authors: Finch, James Kip, 1883-
Subjects: Cartography Military maps
Publisher: New York : John Wiley & Sons, Inc.
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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escribed, but the horizontal angles aretransferred directly to the map and not measured in theusual units. In other words the plotting is done and the map ismade in the field where this procedure is possible and wherethe sketcher has the land in view as he does the work. The methods of flat mapping will first be described, followedby the methods of locating contours. For contours elevationsare necessary and these are secured by actually measuringthe vertical angle, or the angle of one point above or belowanother. For this purpose either a slope board or clinometeris used as will be described in Art. 28. The instruments used for military mapping are containedin a small carrying case or sketch case* and comprise: 1.a small drawing or sketch board, 2. a light tripod, 3. a sightingscale or alidade, 4. a slope board, and 5. paper, thumb * See Appendix 2. THE SKETCH CASE 97 SightingSca/e or Alidade Sketch Board Pencil Slope Board Front - — *-sho wing scalefor vertical angles Carrying case
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Slope Board■— - Rearshowing ReductionDiagram FIG. 55. COMPLETE. SKETCH CASE OUTFIT 98 FLAT MAPPING tacks, pencil, eraser and pins. A complete outfit is shown inFig. 55. The tripod may be fastened to the sketch board bymeans of a small thumb screw like that on any camera tripod.The board can thus be set up at any point, by moving thelegs it can be approximately leveled by eye; with the thumbscrew loose it can be turned in any direction, and by tighten-ing this screw is held firmly in any position. The drawingpaper is secured to the board by thumb tacks. The tri-angular sighting scale or alidade is made of wood weightedwith lead so as to prevent its movement by wind, etc. Pastedon its edges should be a reading scale for the map that is tobe made, and scales of paces also corresponding to the scaleof the map and to the pace-scales of the members of theparty. In fact it is desirable that each man have an alidadewith his own pace scale on it. This alidade serves three pur-poses: 1, it

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