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REDEFINITION OF INDIAN VERTICAL DATUM - DENSIFICATION GTS Levelling was carried out between 1850 to 1905. Indian Vertical Datum was first time defined in 1905. Then no Invar staves were used. No Fore – Back Levelling was done. Most of the BMs established then do not exist on the ground now due to developmental activities and vagaries of the weather. Without Gravity Values. It was assumed that water level of Arabian Sea and Bay of Bengal is same, which is infact different due to different salinity and consequent different density. Levelling was not adjusted in single all India Level Network. Hence necessary to Redefine Vertical Datum. With the requirement of height accuracy within few centimetres and to achieve water flow criterion, we needed to redefine vertical datum.
In past, the requirement of contours was 10 m / 20 m in plain areas and 100 m / 200 m in the hilly area (due to sparse developmental activities) but now owing to population pressure and need for faster development for micro level planning, requirements have increased to get the contour at 50 cm / 1 metre. We are facing more drainage problem, more sewer lines are required, to solve water problem we need to interlink rivers. Essential ingredient in all these works is precise vertical control i.e. precise level line which meets water flow criteria. To achieve this an initiative to redefine the vertical datum for the whole country has been taken up. In this project, it is envisaged to carryout the High Precision Levelling alongwith the gravity observations to obtain the geopotential numbers. These newly defined heights will be based on the geopotential numbers and Helmert Orthometric Heights which are scientifically correct heights and follows the water flow criterion.
- Page 1 and 2: REDEFINING THE HORIZONTAL & VERTICA
- Page 3 and 4: Activities of Geodetic & Research B
- Page 5 and 6: What is Datum? A datum (plural datu
- Page 7 and 8: Geoid Figure of Earth Geoid (Close
- Page 9 and 10: The Ellipsoid The Geoid is a compli
- Page 11 and 12: Horizontal Datum: An Ellipsoid is U
- Page 13 and 14: 2/15/2012 13
- Page 15 and 16: Bureau International de l’Heure (
- Page 17 and 18: International Terrestrial Reference
- Page 19 and 20: IGS Stations 2/15/2012 19
- Page 21 and 22: Status of Horizontal Control in Ind
- Page 23 and 24: Status of Horizontal Control in Ind
- Page 25 and 26: GCP Library Phase-I: Distribution i
- Page 27 and 28: Subsequent Phases Of GCP Library Ph
- Page 29 and 30: Achievements: GCP Phase-II Phase-II
- Page 31 and 32: Network Adjustment Strategy Coordin
- Page 33 and 34: GCP Phase-I Network: Adjusted with
- Page 35 and 36: Accuracy Expected Positional accura
- Page 37 and 38: National GPS Data Centre National G
- Page 39: REAL TIME GPS DATA Under the modern
- Page 43 and 44: Interlinking of Rivers. Flood Contr
- Page 45 and 46: CONCLUSION Provision of dense contr
In past, the requirement of contours was 10 m / 20 m in plain<br />
areas and 100 m / 200 m in the hilly area (due to sparse<br />
developmental activities) but now owing to population pressure<br />
and need for faster development for micro level planning,<br />
requirements have increased to get the contour at 50 cm / 1 metre.<br />
We<br />
are<br />
facing more drainage problem, more sewer lines are<br />
required, to solve water problem we need to interlink rivers.<br />
Essential ingredient in all these works is precise vertical control<br />
i.e. precise level line which meets water flow criteria.<br />
To achieve this an initiative to redefine the vertical datum for the<br />
whole country has been taken up. In this project, it is envisaged to<br />
carryout the High Precision Levelling alongwith the gravity<br />
observations to obtain the geopotential numbers.<br />
These newly defined heights will be based on the geopotential<br />
numbers<br />
and<br />
Helmert<br />
Orthometric<br />
Heights<br />
which<br />
are<br />
scientifically correct heights and follows the water flow criterion.
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