Map Projections

Map Projections

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1921 edition. Excerpt: ...with zenith on the equator; and pass through the straight line representing the equator a plane making an angle 60 with the plane of the projection. Project the net of the zenithal projection orthographically on this plane. We then have a projection of the hemisphere bounded by an ellipse of which the major axis is twice the minor. Now halve the scale in longitude: that is to say, number the meridian which was 10 from the central meridian as 20; and so on. We thus obtain a representation of the whole sphere within the boundaries of the ellipse. The projection is evidently equal area, since we started with an equal area projection, and this property is not modified by the orthogonal projection on to the plane. And it has the advantage over Mollweide's that the angles of intersection of the meridians and parallels are not so greatly altered towards the eastern and western edges of the sheet. It can be constructed very readily when we have a table of the rectangular coordinates of the intersections for the zenithal projection, by plotting the x's unchanged and halving the y's. It is clear that there is a whole class of projections of this kind that might be constructed. But it is only the equal area property that is preserved unaltered in the orthogonal projection on the plane, and only the 2: 1 reduction that offers any special convenience. Breusing's projection. This is an attempt to obtain a mean between the advantages of the zenithal equal area and the zenithal orthomorphic projections. The radii are the geometrical means between the radii of those two projections, or I' = 2 4/tan II(sin Q'. X This formula gives distances from the centre slightly greater than the true distances, but not so exaggerated as in...show more

Product details

  • Paperback | 42 pages
  • 189 x 246 x 2mm | 95g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236911946
  • 9781236911940