. Engineer course in topography. —The clinometer is the instrument forobtaining difference of elevation; it measures slopes. 7. Clinometers are all based on the establishment ofa horizontal reference line by the spirit level or by the plumbob. Trie line of sight is in a vertical plane with the refer-ence line and makes an angle with it equal to the slope be-tween the eye-piece of the instrument and the point uponwhich the sight is taken. A scale of degrees or grades isplaced on the instrument so as to measure the slope and isusually read in reconnaissance instruments at the sametime that the l
. Engineer course in topography. —The clinometer is the instrument forobtaining difference of elevation; it measures slopes. 7. Clinometers are all based on the establishment ofa horizontal reference line by the spirit level or by the plumbob. Trie line of sight is in a vertical plane with the refer-ence line and makes an angle with it equal to the slope be-tween the eye-piece of the instrument and the point uponwhich the sight is taken. A scale of degrees or grades isplaced on the instrument so as to measure the slope and isusually read in reconnaissance instruments at the sametime that the line of sight is adjusted on the distant point. 8. As the slope is usually desired between two pointson the ground itself it is necessary to sight upon a pointabove the distant point a distance equal to the height of theeye above the ground at the time of taking the sight or tomake proper allowance for the height of the eye above theground in calculating the difference of elevation of thetwo ground points. USE OF INSTRUMENTS 31. Plate V 32 TOPOGRAPHY 9. The clinometer often needs adjustment. It shouldbe tested as follows: Mark two points, say 50 feet apart. Put clinometersight on one point and read angle of difference to secondpoint. Put clinometer sight on second point and read angleof elevation to first point. Add the two numerical values,regardless of sign, and divide by 2; the quotient is thetrue reading. For example, if first reading is 2 degreesand second reading 1 degree, the correct reading is Hdegrees. Put clinometer sight line on first point, sight tosecond point, and adjust clinometer until it reads de-grees; or if the clinometer does not permit of adjustmentapply the index error with its proper sign to each reading. 10. Sketching Board and Tripod form simply a smallplane table. The tripod has been found to be not only agreat convenience but is necessary to secure the accuracyinherent in the plane table method. 11. Azimuths are measured in degrees of arc from0 t
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectmilitar, bookyear1922
