project documentation - Introduction Projection Information Data generation for GIS work in Bangladesh is very difficult because there is a different

Introduction: Projection Information Data generation for GIS work in Bangladesh is very difficult because there is a different sets of projection parameters and datum. For the old maps the projections parameters are not well documented which is very inconvenient to work with maps of different times. Because of this inconvenience it is also not possible to use the GIS data from different sources. For the current project “3-Dimensional urban Geological modeling” the following settings has been done for projection. Refference of this settings is Topo map of Survey of Bangladesh (SOB) 2003, scale is 1:5000 scale of greater Dhaka city and surroundings based on aerial photos of Jan 2003 and printed at 2004. Coordinate System Name on Map Bangladesh Universal Transverse Marcetor (BUTM) DATUM Name: Gulshan Ellipsoid Name Everest 1830 Semi-major axis (a) 6377276.345 m Semi-minor axis (b) 6356075.413 Flattening 1/f 1/3008017 SHIFT to WGS84 Molodensky Dx +283.7m Dy +735.9m Dz +261.1m Da +860.7 Df +0.28361368 Vertical Datum Gulshan Datum (newly built) PROJECTION Transvers Mercator Central Meridian 90° E Latitude of origin 0°(equator) Scale factor 0.9996 False Easting 500000m False Northing 0 Information Source Survey of Bangladesh, Nov. 2005, Parameter of the Gulshan Datum GPS no. 303 Ellipsoid WGS84 Everest 1830 unprojected projected in BUTM 23 ° 47 ′ 52.02714 ″Ν 23 ° 47 ′49.48503″Ν N 2631605.718m 90 ° 24 ′ 56.34024 ″Ε 90 ° 25 ′06.55272″Ε E 542625.533m Ellipsoid Height=-45.45m Orthometric Height=8.5344m Bench mark No. 539 and Height is 6.4292m In Bangladesh there is different ellipsoid has been used. A list of different sets of projections parameter has given in the index.

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Ellipsoid Inforemation Ellipsoid Semi major axis m Semi minor axis Inverse flattening 1/f Datum shift parameter, m Remarks Ax Ay Az Source Everest 1830 6,377,276.345 6,356,075.413 300.801700000 289 734 257 Mauelan User Guid Most Text Book 283.729 735.942 261.143 JICA Study 282 726 254 Molondensky Constants Everest Bangladesh 6,377,298.524 6,356,097.518 300.8017 288 735 256 FAP 24 Everest 1948 (or Malaya RTK) 6,377,304.063 6,356,103.039 300.8017 WGS 84 6,378,137.000 6,356,752.314 Projection Information Projection Name Spheroid Central Meridian Latitude of Origin False Northing False Easting Scale Factor User Remarks TM (Transverse Mercator) Everest 1830 90 ° E of Greenwich 0 ° of Equator 0 m 50000 m 0.9998 SPOT XS satellite, FAP6 UTM (Universal Transverse Mercator) Depends on the set up 87 ° E(for zone 45, between 84E-90E) 93 ° E(for zone 46, between 90E-96E) 0 ° of Equator 0 m 50000 m 0.9996 GPS BUTM (Bangladesh Universal Transverse Mercator) Everest Bangladesh or 1830 90 ° E of Greenwich 0 ° of Equator