Topographic maps and sketch mapping . etermination of South with a Watch. when in the field, by day or night, always know the directionof north. This generally comes from a training in observingindications of direction such as the position of the sun, etc., thathas become an almost unconscious habit. This sense of direc- *- . Polaris *X or Nortli Star X Great Dipper / ^x» S K / Pointers Fig. 20.—The Pointers and the North Star. tion is entirely lacking in others and is a thing that childrenshould early be taught to cultivate. Woodsmen note thatmoss prefers moisture and therefore grows best on
Topographic maps and sketch mapping . etermination of South with a Watch. when in the field, by day or night, always know the directionof north. This generally comes from a training in observingindications of direction such as the position of the sun, etc., thathas become an almost unconscious habit. This sense of direc- *- . Polaris *X or Nortli Star X Great Dipper / ^x» S K / Pointers Fig. 20.—The Pointers and the North Star. tion is entirely lacking in others and is a thing that childrenshould early be taught to cultivate. Woodsmen note thatmoss prefers moisture and therefore grows best on the northside of trees, away from the sun. Certain plants such as theCompass Plant and Sow Thistle also arrange their leaves DIRECTION 39 or blossoms in certain directions and probably for similareasons. Directions are stated in several ways. Fig. 21a showsthe scale in a compass box divided to give the points of thecompass. We can thus say that the direction of one pointfrom another is north north east (N N E), etc., (6) shows the. Fig. 21a.—Mariners Compass. usual compass bearing graduation of the surveyor and wewould speak of the same line as having a bearing of N 22|° E,meaning that it is 22f° from the North toward the method of stating the direction is shown in (c).This is known as the azimuth method and the circumferenceis divided from 0 to 360°. The zero point, or zero azimuth, 40 WHAT A TOPOGRAPHIC MAP SHOWS in surveying, is usually taken as North, but in astronomicalwork azimuths are measured from the south point. Notethat when directions are given by azimuth, measured froma zero direction agreed upon, it is necessary to state simplythe angle. Thus for the line mentioned above the azimuth
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectcartogr, bookyear1920
