Unit 1 Part 2 Thacheomatric Surveying..pptx

Thacheometic surveying

1. Surveying Module 1: Part 2 Tacheometric Surveying

2. Course Contents: Tacheometry: Application and limitations, principle of stadia tacheometry, fixed hair method with vertical staff to determine horizontal distances and elevations of points, Study of Total Station

3. TACHEOMETRIC SURVEY 3 SINHGAD INSTITUTE OF TECHNOLOGY AND SCIENCE

4. Tacheometry Principle: Stadia method is based on a principle that the ratio if the perpendicular to the base is constant in similar isosceles triangle. Tacheometric surveying is a method of angular surveying in which the horizontal distance from the instrument to the staff stations are determined from instrumental observations only. Thus the chaining operations are eliminated. Field Work can be completed very rapidly. Tacheometry is mainly used for preparing the contour plans of areas D1/S1=D2/S2=D3/S3= f /i (multiplying constant) F= focal length of object and i= stadia intercept

5. Difference between Theodolite and Tacheometer Used for measurement of horizontal & vertical angle. In theodolite survey , distances are measured by chain or tape. Suitable for plane & hilly area with less obstacles. More stations are required in theodolite survey. Used for measurement of horizontal & vertical distances. In tachometric survey, direct measurement of distances are possible. Suitable in case obstacles like river broken ground. Less stations are required in tacheometric survey. 5 Theodolite Tacheometer

6. Uses of Tacheometry 6 The tacheometric methods of surveying are used with advantage over the direct methods of measurement of horizontal distances and differences in elevations. Some of the uses are: Preparation of topographic maps which require both elevations and horizontal distances. Survey work in difficult terrain where direct methods are inconvenient ,Detail filling. Reconnaissance surveys for highways, railways, etc. Checking of already measured distances Hydrographic surveys and Establishing secondary control.

7. Instruments for Tacheometry 7 An ordinary transit Theodolite fitted with a stadia diaphragm is generally used for tachometric survey. The stadia diaphragm essentially consists of one stadia hair above and the other an equal distance below the horizontal cross-hair, the stadia hairs being mounted in the ring and on the same vertical plane as the horizontal and vertical cross-hairs.

8. 8 Stadia: is a tachometric form of distance measurement that relies on fixed angle intercept. Different forms of stadia diaphragm commonly used

9. Characteristics of Tacheometer 9 The value of multiplying constant f/ i should be 100. The telescope should be powerful, having a magnification of 20 to 30 diameters. The aperture of the objective should be 35 to 45 mm diameter for a bright image. The telescope should be fitted with anallatic lens to make the additive constant ( f+d ) equal to zero. The eye piece should be of greater magnifying power.

10. Principal of Tacheometry 10 The Principal of Tacheometry is based on property of isosceles triangles where the ratio of distance of base from the apex and length of the base is always constant. A O A 2 A 1 B 2 B 1 B C 2 C 1 C ) β In figure, let two rays OA and OB be equally inclined to central ray OC. Let A 2 B 2 , A 1 B 1 and AB be the staff intercepts. OC 2 A 2 B 2 OC 1 A 1 B 1 OC AB = = ……Where f/ i = Multiplying Constant (i.e. 100) = f/ i

11. 11 Different systems of Tachometric Measurement: The various systems of tachometric survey may be classified as follows: The Stadia System (a) Fixed Hair method . (b) Movable hair method. The Tangential system

12. SINHGAD INSTITUTE OF TECHNOLOGY AND SCIENCE 12

13. SINHGAD INSTITUTE OF TECHNOLOGY AND SCIENCE

14. SINHGAD INSTITUTE OF TECHNOLOGY AND SCIENCE 17

15. SINHGAD INSTITUTE OF TECHNOLOGY AND SCIENCE

16. SINHGAD INSTITUTE OF TECHNOLOGY AND SCIENCE

17. SINHGAD INSTITUTE OF TECHNOLOGY AND SCIENCE

18. SINHGAD INSTITUTE OF TECHNOLOGY AND SCIENCE

19. SINHGAD INSTITUTE OF TECHNOLOGY AND SCIENCE

20. SINHGAD INSTITUTE OF TECHNOLOGY AND SCIENCE 27