Topographic maps and sketch mapping . 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 num
Topographic maps and sketch mapping . 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. Fig. 75.—The Sketching Screen. beginner. It consists of a rectangular frame, as shown inFig. 75, fastened to one end of a horizontal bar, the entireapparatus being mounted on a tripod. A series of verticaland horizontal cords divide the opening in the frame intorectangles. When this apparatus is set up, as illustrated inthe figure, and the observer looks through the screen thevertical and horizontal cords will divide the portion of thelandscape, viewed through the frame, into a series of extent of country covered by each rectangle will, of course, 132 LANDSCAPE SKETCHING vary with the distance of the observers eye from the this reason a peep sight is placed in a fixed position atthe other end of the bar and opposite the center of the screen. In using the sketching screen a sheet of paper is ruledwith vertical and horizontal lines just like the lines in thescreen. The process of making a sketch from the landscapethus reduces practically to a problem of trans
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectcartogr, bookyear1920
