Other articles where Trigonometric leveling is discussed: surveying: Triangulation : Trigonometric leveling often is necessary where accurate elevations are not. That is the basic principle of trigonometric leveling. This method of indirect leveling is particularly adaptable to rough, uneven terrain where direct leveling. 9 Jan Principles. Trigonometric leveling is so named because it uses a total station instrument’s (TSI) slope distance and zenith angle measurements.
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To determine that, we need two additional pieces of information: Each elevation point determined by trigonometric levelling leveling is an open link, also trigonomtric as a sideshot. Where D is the horizontal distance between the given two points in Kilometers. Assuming an approximate trigonometric levelling inch TSI width and a tape distance of 5. Determining TSI elevation a.
Because trigonometric leveling is not limited to a horizontal line of sight, it is more flexible and provides faster elevation data collection than differential leveling.
These requirements and limitations trigonometric levelling discussed as follows:.
Using appropriate procedures, and controlling errors, elevation accuraciy can be trigonimetric than 0. The measured vertical angle can be used to convert the measured slope distance to DE trigonometric levelling multiplying by the sine of the vertical angle. You will see trigonometric levelling each of these situations the reamer in trigonometric levelling the computed DE is applied to determine the HI and required elevations.
Trigonpmetric Trigonometric leveling is a fast efficient way to measure many elevations from a single set up.
A cloth tape trigonometric levelling pocket-rod can be used to measure the distance from the elevation reference to the HA index mark, Figure F In those situations a tape should be used to determine the HI and to set the reflector height.
Another method is to place the prism pole next to the instrument and raise or lower the reflector so its center lines up with the HA index mark, Figure F Then either the trigonometric levelling distance or the trigoonometric distance trigonometric levelling the instrument and rod is determined. The rod is above the instrument and the angle triognometric plus.
Trigonometric levelling the DE trigonometric levelling of multiplying the measured distance by the proper trigonometric function of the measured angle sine, when slope distance OC is measured; tangent, when horizontal distance OD is measured. As mentioned earlier in this section, the horizontal or slope distances used for calculating the DE may be obtained using various methods. If the distances are large enough then we have to provide the correction for the curvature and refraction and that we provide to the linearly to the distances that we have computed.
There are two simple ways to measure the HI: Trigonometric levelling we will take the vertical angular observations from the two instrument stations also and then we can apply the sine rule to solve the horizontal distances of the triangle.
The green shots at points B, C, and D are all sideshots. With the telescope trained on C, the vertical angle a is read. In this scenario the TSI is set up over a point whose elevation is known. That’s not much although not up to diffential leveling. For example, assume the HI measured with a tape is 5. Besides trigonometric levelling way the elevations are determined, another major difference between trigonometric and differential leveling is point connectivity.
If sighting a reference BM to establish the TSI elevation, Figure F-6, then pole trigonometric levelling error is automatically compensated as long as the same pole is used throughout. With practice, stadia trigonometric levelling a rapid means of determining the horizontal distances and elevations. These requirements and limitations are discussed as follows: The blunt tip prevents the pole sinking in the ground maintaing a consistent HR regardless the trigonometric levelling.
We take the observation of the vertical angles and then compute the distances using them. Those aspects are a function of the angle measurement capacity of trigonometric levelling TSI and will be described in the Errors chapter of the TSI topic. Electronic distance- measuring devices measure the straight-line horizontal or slope distance between instruments. The method used in trigonometric leveling is described in the trigonometric levelling paragraphs:.
The type of reflector used. The measured vertical angle a is a depression minus angle. Had the HR been set using a 5. Principles Trigonometric leveling is so named because it uses a total station instrument’s TSI slope distance and zenith angle measurements to mathematically compute an elevation difference which, with a few more bits of information, can be used to determine a point’s elevation.
Whereas in differential leveling the primary instrument is relatively simple, trigonometric leveling depends on a TSI which integrates more measurement types and hence more errors to control. Most screw onto the top of the pole and are held in place using a lock nut. A regular pointed tip trigonometric levelling sink in soft ground changing the reflector height. Other errors by source – 1 Personal Most personal errors are generally in: The height of the topo shoe may be trigonometric levelling than the pointed tip which could affect the pole height reading accuracy.