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Figure 8-5.-Stadia Intervalinclined sight.
APPROXIMATE   FORMS   OF   STADIA FORMULAS - 14070_157

Engineering Aid 1 - Advanced Structural engineering guide book
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Figure  8-6.—Ground  elevations:  (A)  Telescope  raised  and  (B)  telescope  depressed. DISTANCE   AND   ELEVATION   FOR INCLINED SIGHTS.— The following example will describe the use of the stadia reduction formulas for inclined sights. Assume you have a stadia interval of 8.45 and an angle of elevation of 25014’, as shown in figure 8-6, view A. Let the instrument constant be 1.0. Substituting the known values in the stadia formula for the horizontal distance, you have h=kscos2a  +(f+c)cosa h = 100  (8.45)  (0.90458)2 +  (1)  (0.90458)  =  692.34 The horizontal distance is 692 feet. Substituting the known values in the formula for the vertical distance, you have v  =  50  (8.45)  (0.77125)  +  (1)  (0.42631) v  =  326.28. The vertical distance to the middle-hair reading on the rod is 326.28 feet. To find the elevation of the ground at the base of the rod,  subtract  the  center-hair  rod  reading  from  this vertical distance and add the height of instrument (HI). (See fig. 8-6, view A). If the HI is 384.20 feet and the center-hair rod reading is 4.50 feet, then the ground elevation  is 326.28  -  4.5  +  384.20  =  705.98  feet If the angle of inclination were depressed, then you would have to add the center-hair rod reading to the vertical distance and subtract this sum from the HI. As you  see  from  figure  8-6,  view  B,  the  ground  elevation would  be 384.2-  (326.28  +  4.5)  =  53.42  feet. STADIA TABLES.— You may save time in finding the  horizontal  distance  and  the  vertical  distance (difference  in  elevation  between  two  points)  by  using the stadia reduction tables in appendix II. Here the 8-6







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