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LEVELLING - Coggle Diagram
LEVELLING
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INTRODUCTION
MSL vary with locations due to wind,
current and tides
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In Malaysia tides are observed at 21 tidal gauge stations distributed throughout the country in order to obtain the MSL
Heights are based from the mean sea level (MSL) level (MSL) - normally referred to as normally referred to as datum
OBJECTIVES
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To establish the vertical control and reduce level for station that are involved in traverse at the project area
SUMMARY
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Any other readings/observations contained between the backsight and foresight are called intermediate sights
Only backsights and foresights are used when flying levels (i.e. when determining a when flying levels (i.e. when determining a TBM or BM.)
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TERMINOLOGIES
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Bench Mark (BM) – permanent markers with accurate reduced levels. In Malaysia Terminologies these are provided by JUPEM
Temporary Bench Mark (TBM) – temporary markers established normally near construction sites. In particular if site is too far from a BM
NOTES
Backsights and final foresights must be made to a point with known RL, such as, BM or TBM
Points that are to be TBM or BM must not be observed as intermediate sights – this is to ensure that systematic errors are minimised (will be explained later)