Topographic surveying; including geographic, exploratory, and military mapping, with hints on camping, emergency surgery, and photography . Elevations by Stadia.—Table X„computed by Prof. R. S. Woodward, is one of the mostconvenient for determining differences of elevation frommeasures made with stadia. This table is computed from the formula /^ = ^ sin a cosin «-; .... (12) in which d is the observed distance of the rod, a is the angleof elevation or depression, and h is the difference of eleva-tion. To use the table, look for the observed angle in thefirst column, and the distance in the upp
Topographic surveying; including geographic, exploratory, and military mapping, with hints on camping, emergency surgery, and photography . Elevations by Stadia.—Table X„computed by Prof. R. S. Woodward, is one of the mostconvenient for determining differences of elevation frommeasures made with stadia. This table is computed from the formula /^ = ^ sin a cosin «-; .... (12) in which d is the observed distance of the rod, a is the angleof elevation or depression, and h is the difference of eleva-tion. To use the table, look for the observed angle in thefirst column, and the distance in the upper line under Z? ;, DIAGRAM FOR REDUCING STADIA MEASURES. 2$g the differences of elevation will be found at the intersectionof the two columns. Example: Assuming the observed distance read directlyfrom the stadia-rod as 360 feet and the angle 2° 40, wehave from the table directly the result /i = 16. y feet. 109. Diagram for Reducing Stadia Measures.—Stadiameasures may be reduced by a diagram more simply, thoughnot with the same degree of accuracy, as by tables. Thefollowing diagram (Fig. 78), from Ira O. Bakers Engineers SCO. Fig. 78.—Stadia Reduction Diagram. Surveying Instruments, gives directly the corrections tohorizontal distances in the upper horizontal line correspondingto the observed distances on the left-hand vertical line, andthe angles indicated by diagonal intersecting lines. Theright-hand vertical column of figures are differences of eleva-tion. These are found by the intersection of the lines of 26o STADIA TA CMYMETR Y. Tabledifferences of elevation D D D I) D I> n X» I> J) I* J> D X) a 100 110 120 130 110 150 l(iO 170 180 190 200 220 240 260 o /o OI o 02 0 03 0 2 0 04 0-3 0 05 °-3 0-3 0
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