Title 114 Stadia Surveying.pdf ✅

MSTC 114: Stadia Surveying 1. Stadia A transit is a sighting instrument that can be rotated horizontally and vertically. Thus, it is used to measure both horizontal and vertical angles. The reading of a transit looks like this: The difference between the upper and lower readings is the stadia intercept. The stadia interval factor is the ratio of the stadia intercept to the distance between the focal point and the rod. Since transits use lenses, the light going to it focuses on a single point. The distance from the center of the instrument is the stadia constant. The stadia constant of internal focusing telescopes is zero since it is manufactured in a way that light focuses inside the instrument. 2. Horizontal Line of Sight Let the stadia interval factor be K, the stadia intercept be S, and the stadia constant be C. The distance between the instrument and the center of the reading is d = KS + C 3. Inclined Line of Sight When transits are used on a slope inclined by an angle θ, the stadia intercept is not perpendicular to the line of sight. The stadia intercept and the line of sight must be perpendicular to use the previous equation. Thus, to find the stadia intercept perpendicular to the line of sight, S ′ = S cos θ
For the measured distances, ID = KS ′ + C ID = KS cos θ + C For the vertical and horizontal distances, H = ID cos θ V = ID sin θ 4. Sensitivity of Bubble Tubes When the bubble of the level is not exactly in the center, the line of sight is a bit off. If the distance between the telescope and the rod is d, then the distance x the reading is off can also computed by the arc of a circle. x = dθ When the telescope is so off that the bubble moves n spaces, the angle subtended by one space is α = θ n The radius of curvature is the length required to subtend an arc of one space on the bubble level. s = Rα