Methodology and execution Plan of Topographical Survey

 This Methodology and execution Plan of Topographical Survey, covers the following works

(1) Installation of Benchmarks

(2) Topographical survey at with scale 1 : 500 and grid every 10 m interval.

(4) Topographical surveys for Pipeline route, with scale 1 : 500 and grid every 100 m interval.

Installation of Benchmark

The purposed of Benchmark establishment is intended to be used as a permanent point over the field, that point

in future particularly during the construction stage can be used as reference point within stake out stage.

The Benchmark will be installed on the stable area, easily identified and reachable. Shape and size of

benchmark are planned to have dimensions or 30 cm x 30 cm x 120 cm for temporary Bench Mark, and shall

founded on piles or shall based on geotechnical calculation.

 

METHOD STATEMENT

Elevation of Benchmarks

Elevation of benchmarks will be decided by direct leveling survey. A leveling route for measuring

benchmarks will be selected in such a way that the route starts from existing benchmark, and return

either to the original benchmark or another existing benchmark in the area

1. Observation

(1) Two way observations by level using a pair of staff will be carried out. Lengths of foresights and

back sights will be kept very nearly equal. As a rule, the length will be not exceeding 70 m.

(2) Reading of observation values will be made in millimeters.

2. Limits In Observation Value

(1) Limits in observation value in leveling will be as follows:

Error of two way observation 20 mm or less for each 1 km.

Error of closure 15 S mm or less

Where S is one way distance in kilometer.

(2) When the error of closure falls within the specified limits, it will be distributed equally over the

survey points in proportion to the distance between survey points.

(3) When the error of closure has exceeded the specified limits investigate the causes

thereof and carry out re surveying.

 

Construction of Station and Benchmarks

(1) The stations and benchmarks will be carefully constructed after approved by the COMPANY.

(2) The Stations and benchmarks will be provided with adequate protective fences to preserve

them during construction terms.

(3) The stations and benchmarks will be clearly marked with item number, elevation and / or

coordinate.

 

Control Point Survey

Control point survey will be carried out to produce fixed coordinates of each control point referred to

the reference point subjected by the Company Engineer.

 

TOPOGRAPHICAL SURVEY

(1) Topographical survey will be include of horizontal control survey, vertical control survey and survey the

whole site using cross section in every 10 meters.

(2) Topographical map will show horizontal detail and elevation of the ground.

Horizontal Control Survey

(1) Sufficient number of control benchmarks for detail will be installed.

(2) Location of the control benchmarks will be decided by site reconnaissance

(3) All coordinates of control benchmarks will be decided according to the existing benchmark

by means or traverse survey.

(4) Accuracy of coordinate of existing benchmark will be confirmed by traverse survey.

Vertical Control Survey

(1) Sufficient number of temporary benchmarks will be installed for the whole site survey of areas.

(2) All elevation of the temporary benchmarks will be decided according to the existing benchmark by

means of direct leveling survey.

 

The Whole Site Survey, Cross / Longitudinal survey

(1) Horizontal and vertical detail of areas will be surveyed based on the control

benchmarks.

(2) Cross section will be surveyed by direct levelling at 25 m interval.

(3) Total Station or Combination of T-2 Theodolite and EDM will be used to collect data of cross

section.

(4) Beginning Point (BP), Intersection Point (IP) and Ending Point (EP) will be set out of each cross

section line from the nearby control point.

(5) Wooden peg or concrete marker will be established for each marking BP, IP and EP.

(6) Traversing and levelling work will be carried out to preserve coordinates and elevation of BP,IP

and EP referred to existing BM.

(7) The measuring intervals of cross section will be 5 to 10 m and all remarkable changes of

topography will be measured.

(8) All fields will be carefully recorded for further processing.


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