Descriptive geometry . ction, will be designated by the letter P. Thisplane has already been defined as a plane perpendicular to theground line (§ 35), that is, P is perpendicular to both H andV. Hence the three planes H, V, and P form a system ofmutually perpendicular planes (Fig. 64), intersecting in a / A V // ?// // / HV / / i1 * // / // / A / 0 U/~ ti-?-t x / 4-i 3 ii i / 7^ / t 7 H / 1 L_ Fig. 04. common point o, and intersecting each other by pairs in threemutually perpendicular lines, IIV, IIP, and VP, all passingthrough o. The intersed ion, IIV, of //and Fis the ground line. 53. A Pro
Descriptive geometry . ction, will be designated by the letter P. Thisplane has already been defined as a plane perpendicular to theground line (§ 35), that is, P is perpendicular to both H andV. Hence the three planes H, V, and P form a system ofmutually perpendicular planes (Fig. 64), intersecting in a / A V // ?// // / HV / / i1 * // / // / A / 0 U/~ ti-?-t x / 4-i 3 ii i / 7^ / t 7 H / 1 L_ Fig. 04. common point o, and intersecting each other by pairs in threemutually perpendicular lines, IIV, IIP, and VP, all passingthrough o. The intersed ion, IIV, of //and Fis the ground line. 53. A Profile Projection. Let the model of some familiar object, such as a cabin, be placed on the horizontal plane in tlic first quadrant, li.^r. l. Let the front and hack be parallel to the F-plane, and the ends parallel to P. Let a view be taken D ;j3 34 DESCRIPTIVE GEOMETRY [VI, § 53 looking in the direction of the arrow, that is, from right to such a view, the whole surface of P will be seen, while the. Fig. m (repeated).F-plane will be seen edgewise as a vertical line, the //-planeedgewise as a horizontal line, and only the right-hand end ofthe cabin will appear. The actual end view is shown in Fig. 65. No boundary isshown in this figure for the P-plane, since it, like the H- and /\ PFig. 65 F-planes, is of indefinite extent. The quadrants will appearas indicated by the numbers, and must always so appear whenP is viewed from the right. In this end or profile view of VI, § 54] THE PROFILE PLANE 35 the cabin, both heights and widths, or, in other words, all dis-tances perpendicular to // or to V are shown in their truesize. Hence in this view the actual distances from the objectto H and to V are necessarily shown. 54. Relation of the Profile Projection to the H- and 7-Pro-jections. Figure 66 shows the construction of the end view, or ric Showing \Jht hand end AP < X * A /rv~: Front 11 Back 1 £ •< H 1 \ \ \ i 4- \\\\ 3 Ah \\\ < V Fig. 66. profile projection, of
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