Plane Surveying: A Text-Book and Pocket Manual
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from ... Show synopsis This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1907 Excerpt: ... section at EE. There is nothing shown by this section which is not evident from a study of the contour-lines. On the contrary the contour-iines show the exact shape of the hill better than the section From the latter, one might suppose the ground to run in the form of a ridge, but from the contours it is seen to be a coneshaped MIL Question. If the hill were a perfect cone, would the contour-lines be perfect circles with a common center? 399. Contour-lines, Fundamental Principles. 1. All points on the same contour-line have the same elevation. 2. Two contour-lines of different elevations cannot cross each other. If they did, the point of their intersection would have two different elevations, which is absurd. (How can an overhanging cliff or a cave be an exception to this rule?) Contourlines of different elevations sometimes appear to merge in one line as in the case of a vertical cliff. 3. Two different contour-lines of the same elevation cannot merge and continue as one line. For the single line would indicate a knife-edge ridge or depression, something which does not occur in nature. Different contours of the same elevation, 'however, often approach very near to each other. 4. Contour lines near together indicate a steep slope, --far apart a gentle slope, --equally spaced a uniform slope. It is evident that the horizontal distance between successive contourlines indicates the rate of slope. 5. A contour passing through any point is perpendicular to the line of steepest slope at that point. This agrees with (4), since the perpendicular distance between contour-lines is the shortest distance. Ridge and valley lines cross contours at right angles, 6. A closed contour-line with one or more higher ones inclosed indicates a hill Fig. 398); with one or more lowe.