Topographic maps and sketch mapping . o d a bFig. 73.—Perspective of a Circular Path. spacing of the poles of the telegraph line becomes smallerand smaller the further they are away. Now note the deline-ations shown above for fences, roads, etc., and how this sameperspective effect is secured. Another feature in perspective is shown in Fig. 73. Imaginea circular driveway or track. The perspective appears widerin the foreground ah than at the back cd as shown in thesketch, due to the fact that the angle subtended at the eyeby the two edges of the roadway is greater for the nearerportion. Also n
Topographic maps and sketch mapping . o d a bFig. 73.—Perspective of a Circular Path. spacing of the poles of the telegraph line becomes smallerand smaller the further they are away. Now note the deline-ations shown above for fences, roads, etc., and how this sameperspective effect is secured. Another feature in perspective is shown in Fig. 73. Imaginea circular driveway or track. The perspective appears widerin the foreground ah than at the back cd as shown in thesketch, due to the fact that the angle subtended at the eyeby the two edges of the roadway is greater for the nearerportion. Also note that the sides at e and / appear their 130 LANDSCAPE SKETCHING. J THE SKETCHING SCREEN 131 full width. Applying these same principles to the case of awinding stream we understand how the stream shown in is drawn. Fig. 74 shows a landscape sketch and illustrateshow various delineations are combined to produce a cleardrawing when due allowance is made for perspective the varying size of the delineations and also the varia-tion in the thickness of the line used which, together with therough indication of foreground objects, gives the effect ofdistance. EXERCISES 1. Copy Fig. 71. 2. Draw the required number of vertical lines one inch apart and horizontal lines at half this distance and enlarge Fig. 74 by the same process fol-lowed in the method of squares, Art. 21. Art. 31. The Sketching Screen The sketching screen is a device which is never used bythe experienced sketcher but is of value in assisting the
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectcartogr, bookyear1920
