Topographic, trigonometric and geodetic surveying; including geographic, exploratory, and military mapping, with hints on camping, emergency surgery, and photography
Herbert Michael Wilson
Paperback
(RareBooksClub.com, March 6, 2012)
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. 1912 Excerpt: ... those of Mercator, Lambert, and Bonne. An ordinary or equidistant conical projection based on a tangent cone shows the meridians as straight lines proceeding from the apex of the cone at equal angles, while the parallel circles are equal-spaced circular arcs with the same apex as center. (Fig. 130.) In Mercalor's conical projection the distortion is diminished by making the cone pass through two parallels of the area to be represented, so that two parallels of the sphere, instead of one, coincide with their pictures. (Fig. 131.) This is the projection on which the maps of our common atlases Fie and geographies are drawn. Lambert's equivalent conical projection is based on an intersecting cone, and the distances of the parallels increase with increase of latitude at such rate that the meshes included by them and the meridians show the same areas as on the sphere. (Fig. 132.) Bonne's projection is a projection on the tangent cone in the.center of the map, the parallel curves being drawn in the same way as in the ordinary conical projection. On these parallel curves, on both sides of the meridian, the parallel degrees are marked in their true size, and the points of intersection are joined by steady curves which give the meridians. (Fig. 133.) 184. Constructing a Polyconic Projection.--The polyconic projections is that best suited to accurate topographic or geographic mapping as it corresponds most nearly to the spheroidal shape of the earth. It is the projection of a series of cones parallel to each parallel of latitude to be drawn on the map. Assume the scale of the map as one mile to one inch, or 1: 63,360. For this scale it will be sufficient to draw the meridian and latitude lines at intervals of every five minutes or approximately five inches apart, tho...