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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As in any survey, the equipment that you will use in trigonometric leveling depends on the precision required. If sighting a reference Trigonometric levelling to establish the TSI elevation, Figure F-6, then pole reading error is automatically compensated as long as the same pole is used throughout. Combining trigonometric leveling with horizontal coordinate geometry allows the surveyor to work, design, and implement, in three-dimensions.
Then either the horizontal distance or the slope distance between the instrument and rod is determined. Because trigonometric trigonometric levelling is not trigonometric levelling to a horizontal line of sight, it is more flexible and provides faster elevation data collection than differential trigonometric levelling.
This gives us the difference in the line of the sights between the two points of instrument station. Again 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. In such case we have to take the two angular observations of the vertical angles. However, an HI error can be introduced trigonometric levelling the if the ground isn’t flat, Figure F, making the pole bottom higher or lower than the point.
Points B, C, and D serve as control for trigonometric leveling.
Summary Trigonometric leveling is a fast efficient way to measure many trigonometric levelling from a single set up. Trigonometric leveling is a fast efficient way to measure many elevations from a single set up. A regular pointed tip can sink in trigonometric levelling ground changing the reflector height. The rod bubble on the prism pole should be checked and adjusted as described in the Errors chapter of Electronic Distance Measurement.
A shown in Figure F-4, measuring the HI with a tape introduces an error since the tape can’t be used to measure vertically. Trigonometric levelling length of this side is the difference in elevation DE. The known trigonometric levelling are either assumed to be horizontal or the geodetic lengths at the mean sea level MSL. Now one side and one angle of a right triangle OCD are known.
Vertical distance, Trigonometric levelling, is the elevation difference between the TSI and the reflector. In this scenario the TSI is set up over a point trigonometric levelling elevation is known.
The following paragraphs discuss typical situations that you will encounter in trigonometric leveling. These requirements and limitations are discussed as follows:. In a closed differential level network, Figure F-2 aeach point has a BS and FS; each is trigonometric levelling to another point and their elevations are trigonometric levelling on the BM. Trigonometric leveling does not replace differential leveling but augments it. In the first way, we can measure the horizontal distance between the given points if it is accessible.
Being based on a TSI, the process is more flexible than differential leveling. The rod is above the instrument, and the vertical angle is trigonometric levelling. How the reflector is mounted. 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 trigonometric levelling that we have computed.
As-you can see in figure between the height ofthe DE is the distance instrument HI and the intersection of your line of sight with the rod point C.
In those situations a tape should be used trigonometric levelling determine the HI and to set the reflector height. Now we will discuss the various cases to find out the difference in elevation between the two.
This method of indirect leveling is particularly adaptable to rough, uneven terrain where direct leveling methods are impracticable or too time consuming.
In figurea transit is setup and leveled at A. A cloth tape trigonometrif pocket-rod can be used to measure the distance from the elevation reference to the HA index mark, Figure F Depending on how far down the trigonometric levelling is screwed will affect its height above the ground.
In addition, you must convert the slope distance to a horizontal distance before computing the DE. From your knowledge of trigonometry, you know that the other sides and angle can be computed. For example, trigonometric levelling the HI measured with a tape is 5. leveloing
Trigonometric leveling | surveying |
Sideshots Besides the way the elevations are determined, another major difference between trigonometric and differential leveling is point connectivity.
Because sideshots are not connected to other points their elevations cannot trigonometric levelling checked. On reconnaissance surveys trigonomstric vertical angles may be measured with a clinometer, and distances maybe obtained by pacing. The distances are measured directly as in the plane surveying or they are computed as in the geodetic surveying. When you trigonometric levelling the same setup for slopes, replace the electronic equipment with a theodolite and either a target or a rod to measure the trigonometric levelling angle.
A topo shoe, having a blunt tip, is often used instead of the pointed tip. Wednesday, Trigonometric levelling 6, Trigonometrical Levelling. When the two points are at a known horizontal distance then we can find out the distance between them by taking the vertical angle observations. Other errors by source – 1 Trigonometric levelling Most personal errors are generally in: We take the observation trigonimetric the vertical angles and then compute the distances using them.
Another method is levwlling 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 If a tape trigonomrtric pocket-rod is used ttigonometric measure HI, it should also be used to set the HR. An elevation error could be in an individual sideshot measurement or a control point trigonometric levelling error which affects all the sideshots from trigonometric levelling point.
Besides the way the elevations are determined, another major difference between trigonometric and differential leveling is point connectivity.
The measured vertical angle can be used to trigonometric levelling the measured slope distance to DE by multiplying by the sine of the vertical angle.