Categories
land surveying

Dumpy Level – Land Surveying

  • The simplest type is the Dumpy Level in Land Surveying,the basic components of which are:-
  • A tripod upon which the instrument is attached for use.
  • A tribach, or alternatively a ball and socket, which is used to bring the telescope into a near horizontal position.
  • In dumpy Level, A telescope, fitted with a diaphram on which cross-hairs are etched to define the line of sight.
  • A bubble tube, attached to the telescope tube, and used to determine when the line of sight is horizontal.

 

Tripod

The tripod consists of three pointed legs, (wooden or metal), with a solid metal head. The legs may be rigid or telescopic.

For good leveling it is essential that there be no movement or free-play in any of the joints. The metal feet on the legs, the sliding joints of telescopic legs and the hinged attachments
to the head should be checked and adjusted regularly.

Wooden legs should be painted at least once each six months with a 50/50 mixture of linseed oil and turpentine.

 Tribach

The tribach consists of two plates (one upper – the other lower) joined by three adjustable foot- screws.

The tribach is permanently fixed to the telescope and its axis, in such a way that the upper plate is parallel to the telescope tube.

The three foot screws are manipulated to bring the upper plate and the telescope into a horizontal position.

The tribach may be screwed onto the head of the tripod, or alternatively a central screw within the tripod head may be screwed into the base of the tribach.

For “quickset” levels the three screw tribach is replaced by a ball and socket unit which performs the same function.

The upper plates of tribachs or ball and socket units may be fitted with a small pea, or centre bubble, so that quick approximate setting up of the instrument can be carried out.

The tribach should fit firmly to the tripod head with no free-play and there should be no sloppiness in the movement of foot-screws. A protector for the tripod head screws is provided and should always be used. Foot screws should be kept free of dust and lightly oiled with fine oil as required.

Categories
land surveying

Survey Methodology

Traverse Survey
At the commencement of contract all the basic traverse points will be checked with engineer and if any are found to be missing or appear to have been disturbed, necessary arrangements will be made to re-establish

the points and traverse survey is carried out and if any adjustments would be found which would be done with the Engineer. Subsequently control point coordinates would be submitted to the Engineer for approval.

TBM Survey
Initially the Engineer’s/Employer’s occurrence will be sought to obtain details of permanent bench marks tied with national grid. Temporary bench marks will be established at the rate of four per km and also at or near all structures and TBM list and levels would be submitted to the Engineer for the approval. Checks would be carried out on these bench marks once every month and adjustments, if any should be agreed with the Engineer. An up-to-date record of all bench marks including approved adjustments would be maintained with the Engineer.

Center Line Setting out and Marking
Using total stations and approved coordinates of control points, the road center line would be marking at every 10m interval on the road jointly with the Engineer. Chainage would be marked on the road center line in each 20m and 100m interval with meter and kilometer interval respectively.
With the aid of rope and road marking paint, the center point marked in every 10m intervals of the road would be extended as a center line and that established centerline would be maintained until the end of the project.

Correction
According to the Engineer’s instructions, corrections if any would be made and which would be followed for the remaining work.

Cross Section Survey

The cross section survey would be commenced as soon as center line is marked and approved by the Engineer. Levels of the cross section will be taken at every chainage point marked on the center line. Cross sections at 20m intervals and in special cases such as sharp curves; the cross section intervals reduced to 10 meters will be submitted to the Engineer’s approval. At the same time, for plotting of longitudinal section (LS) the center value of each cross section would be used.

Submission of Drawings

Initial cross section drawings plotted on A4 sheet on scale of 1:1000 both vertical-horizontal and longitudinal profiles of the road (both hard & soft copy) would be submitted to the Engineer along with back up data sheets for approval.

Calibration

(a) Level Instrument
Calibration certificate for brand new level instrument is given by the manufacturer and two peg level tests on the leveling instrument would be carried out once in a month and if we would find any error in instrument during working, immediately we would be attending to the calibration of the instrument.

(b) Total Station
Calibration certificate for brand new total station is given by the manufacturer and once in an every six month period, the calibration would be carried out until the project end accordance with relevant standards and if we would find any defect in instrument during working, immediately we would be attending to the calibration of the instrument.

Categories
land surveying

Surveying Methodology

SURVEYING METHODOLOGY

 

Introduction
Generally the entire construction project involves surveying, the following steps are proceed in road construction projects to covers the Traverse Surveying, Temporary Bench Mark Surveying, and Center Line Setting out, Center Line marking, Cross Section Survey and Submittable of Drawings.

Abbreviations

TBM – Temporary Bench Mark

GA – Government Body

Traffic Safety Management & Control

 

Safety Awareness Meeting

Safety awareness meeting has to be conducted every working day morning/every other day to brief the work force in the safety prevention measures. Traffic Safety will be discussed as a topic. Each survey group should be well awarded to follow specified instructions such as “Barricading Boards” and signalmen will be deployed to control the traffic flow during working time. The survey team should have practical knowledge to adjust following specified instructions that will not meet.

 

Operating Procedure

Site investigation has to be carried out for safety precautions prior to commencement of the work, in order to display relevant sign boards.

  • Men at work 75m-100m ahead” sign boards would be placed on both left hand side of the road.
  • 25 m away from men at work sign Narrow Road/one lane traffic sign would be placed in order to notify the drivers with regard to road situation.
  • Working area will be corded off with traffic cones to indicate setting out survey for the oncoming traffic to see on both sides.
  • “One way traffic ahead” sign boards would be placed 90m ahead of working area in order to notify oncoming drivers.
  • Traffic controllers would be deployed on both sides in order to control “one way traffic”.
  • Photographs would be taken to disseminate and maintain traffic safety records.
  • Radio communication system would be used where normal communication is impossible.
  • After completion of the work, safety cones and barricade boars has to be removed accordingly.

General Traffic Arrangement will illustrate

 

In addition to following safety precaution has to be adopting to minimize accidents that can be happened.

 

  • Safety helmets, traffic safety vests, boots, dust mask & gloves will be provided.
  • Warning sign boards would be displayed through out the site.
  • Monthly safety awareness program & training program would be conducted.
  • First aid facilities would be provided.
  • Safety officer has to visit the sites twice a day and required safety measures will be adopted at site. In addition, work discrepancies will be discussed in the following day morning at the safety meeting

Resourses

Man Power

2 Site Engineers

2 Nos. Total Station

1 Safety Officer

4 Nos. Survey Staff

4 Surveyors

2 Nos. Level Instrument

22 Skill Laborers

Equipment & Hand Tools

8 Flagmen

3 Nos. Tape (30m)

6 Nos. Tape (5m)

24 Nos. Traffic Cone

1 No. Rope (30m Length)

6 Nos. Safety Sign Board

4 Nos. Walkies Talkie

1 Narrow Road Traffic Safety Sign Board

Material

Road Marking

Concrete Nails