Why it was necessary? Geodetic Datums. Type of Geodetic Datum. Nothing but spheroid of origin. We need. Local Datum Definitions in Dubai Emirate

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1 Why it was necessary? Dubai Eirate Between Clark880 and Spheroid.Al Marzooqi, H.Fashir, Syed Iliyas Ahed ( Dubai, United Arab Eirates ) About 9000 control points were available on Clark880 UTM Whole ilitary and border inforation were on Clark880 In the year 999 DM switch over to spheroid and new projection called DLTM was introduced on the sae spheroid started connecting old control station Survey section Unfortunately for CAD purposes counity wise paraeters were developed There were no single universal paraeters for datu transforation available Geodetic Datus Type of Geodetic Datu Nothing but spheroid of origin We need A local datu is the best fit to the Geoid in a particular region Spheroid paraeter : a, f Origin : o,o,o Local Geodetic Datu (Topocentric) Orientation of axis :Rx, Ry, Rz The global datu is a best fit to the Geoid over the whole earth Global Geodetic Datu (Geocentric) LOCAL DATUM Local datu are classified as Horizontal and Vertical datu Horizontal Datu A horizontal geodetic datu ay consist of the longitude and latitude of an initial point (origin); an aziuth of a line (direction) to soe other triangulation station; the paraeters (radius and flattening) of the ellipsoid selected for the coputations; and the geoid separation at the origin Vertical Datu Vertical datu provides the reference to easure the height Local Datu Definitions in Dubai Eirate Spheroid : Clark880 Sei Major Axis (a) Sei Minor Axis ( b ) Flattening ( /f ) Datu : Nahrwan Vertical Datu : DMD Port Rashid Datu Projection Paraeters of Clarke 880 UTM ( Universal Transverse Mercator ) one 40 False Northing 0.00 False Easting 500,000 Origin Latitude 0.00 Central Meridian (CM) 57 E Scale Factor on CM

2 GEOCNETRIC DATUMS Geocentric coordinates syste Their geoetrical center corresponds with the Earths center of ass or geocenter. Geocentric datu is one which best approxiate the size, shape and Geoid of the earth as a whole. The first set of coordinates defined by the Major earth axis :the axis around which the earth is spinning. Second axis is: to define by the intersection of circle equatorial plane and the Greenwich eridian. 3 The third axis is the plane akes R.H.S. with the two Defining the origin for curvilinear coordinates Latitude, Longitude and Height. If the earth's spheroid sei ajor axis is a, sei inor axis b, and inverse flattening /f, then = ( ν h)cosφ cos λ = ( ν h) cos φ sin λ = ( ν ( e ) h) sinφ h = H N ϕ DQGλ DUHUHVSHFWLHO\WKH ODWLWGHDQGORQJLWGHUHODWHGWR WKHSULPHPHULGLDQRIWKHSRLQW KLVKHLJKWDERHWKHHOOLSVRLG VHHQRWHEHOR where is ν the prie vertical radius of curvature at latitude ϕ and is equal to HLVWKHHFFHQWULFLW\RIWKHHOOLSVRLG Where h = Ellipsoidal Height H = Orthoetric height, N = Geoid-ellipsoid Separation ADVANTAGES OF THE GEOCENTRIC DATUM A geocentric datu has the center of the earth as its origin Supports the latest survey techniques and provides a odern and accessible positioning fraework, free of distortion for ost practical purposes. Provides global integration and supports the direct use of satellite positioning systes such as GPS No transforation will be involve Easy to establish link with the any international datu Spatial data can be used directly by GIS users Brief History DATUMS AND PARAMETERS USED WORLD WIDE NAME EQUATORIAL RADIUS FLATTENING WHERE US ED Krassowsky (940) 6,378,45 /98.3 Russia International (94) 6,378,388 /97 Europe Clarke (880) 6,378,49 /93.46 France, Africa, UAE Clarke (866) 6,378,06 /94.98 North Aerica Bessel (84) 6,377,397 /99.5 Japan Airy (830) 6,377,563 /99.3 Great Britain Everest (830) 6,377,76 / India WGS 66 (966) 6,378,45 /98.5 USA/DoD GRS 67 (967) 6,378,60 /98.5 AustraliaAustralia WGS 7 (97) 6,378,35 /98.6 USA/DoD WGS 84 (984) 6,378,37 /98.57 WORLD WIDE Adoption of Geocentric Datu in Dubai Dubai Eirates Survey network control based on Old Trucial Coast Countries 3 rd order Geodetic Control on CLARK880 Ellipsoid, setup during s developents of Eirates deanded survey control and apping very extensively which resulting a ajor observation of survey networks, by Triangulation, traverse and Trilateration. During and subsequent Aerial Photograetric apping in 983 on Clark880 During 979 using Doppler technique three stations observed on WGS7 Spheroid. In the year 99 the first order Geodetic GPS Network on Spheroid was established (using transforation fro wgs7 to wgs84). Total 6 onuents were observed. 995 is the year where Dubai adopted ITRF-93 a geocentric datu.a land ark in the history of Survey of Dubai.

3 Establishent of Absolute ITRF Station in Dubai Main Control Network I T R F 93 - GPS NETWORK 4 Stations in Dubai (ET8, ET5, BP5, ET45) (ET5) In and in Fujera 3 IGS Reference Stations (Graz Austria, Metera Italy and Kitab Uzbegisthan) Planning and Observation by Institute of applied Geodesy (IfAG) - Gerany and DM Lack of geoid inforation Datu transforation proble Non unifority of control distributions Different class of station accuracy In hoogeneity of control Datu Transforation To transfor one datu to another we ust know the relationship between the chosen ellipsoids in ters of position and orientation. The relationship is is defined by 7 constants. o 3 translation Distance of the ellipsoid center fro the center of the earth (,, ) o 3 rotations Rotations around the,, and of the Cartesian Coordinate Syste Axes (ε, ψ, ω) o scale factor Scale change (S) of the survey control network Also can work with the following cobination For working purposes a Bi-cubic 6 paraeter were attepted. They developed a ethod to estiate the paraeters using siple interpolation procedures, but accuracy was in 3 range Translations (3 Paraeters) Moveent of points along an Axis Rotations (3 Paraeters) Moveent of points around an Axis ω ε ψ 3

4 S Scale ( Paraeter) Changing the distance between points R = sc R R R,,,, Sc,, R, R, R 7 Paraeter Transforation between two Datu R R Cartesian coordinates of Datu Cartesian coordinates of Datu The scale difference between the coordinates systes The difference between the centers of the two spheroids The rotations around the three coordinates axes, Rotations are positive anticlockwise about the axes of Datu coordinates syste when viewing the origin fro the positive axes Effect of Geoid Inforation Coparison of WGS and Clark Spheroid = ( ν h) cos φ cos λ = ( ν h) cos φ sin λ = ( ν ( e ) h) sin φ where h=hn If N= 0, Then h=h = ( ν H ) cos φ cos λ = ( ν H ) cos φ sin λ = ( ν ( e ) H ) sin φ If N 0 = N cos φ cos λ = N cos φ sin λ = ( ν( e ) N) sinφ, WGS 84 WGS 84, The Bursa-Wolf Transforation Model Is a seven-paraeter odel for transforing three-diensional Cartesian coordinates between two datus The transforation involves three geocentric datu shift paraeters (,, ), three rotation eleents ( R, R, R ) and scale factor ( L ). L = R R L R L CLK, CLK, CLK : are the local datu (CLARK) Cartesian co-ordinates. :are the global datu () Cartesian co-ordinates; CLK CLK CLK WGS WGS WGS d L R 84 = d L d R n = i n i = n = i n i = R L n = i n i= The Molodensky-Badekas Transforation Model Is also a seven-paraeter odel for transforing three-diensional Cartesian coordinates between two datus The transforation also involves three geocentric datu shift paraeters ( d, d, d ), three rotation eleents ( R, R, R ) and scale factor ( ). L Where clk clk clk i, i, : are the Cartesian co-ordinates in the local Clark syste; i n : is the nuber of coon points. 4

5 Coon Points on / Clark 880 Spheroid Transforation Coputation Residuals Table For 966 Coon Points - Mainland Transforation Coputation Residuals Table For 88 Coon Points at 3744 Points Converted to Clark 880, Using Paraeters and Copared With Observed Value Mainland 3744 Points Converted to Clark 880, Using Paraeters and Copared With Observed Value 9 Points Converted to Clark880, Using Paraeters & Copared With Observed Value Mainland 5

6 Accuracy after Transforation using the Transforation Paraeters Statistical Quantities for 7 Paraeters (Molodesky-Badekas & Bursa-Wolf) Mainland Main Land Statistical Quantities for 7 Paraeters (Molodesky-Badekas & Bursa-Wolf 7 Transforation Paraeters 7 Transforation Paraeters Transforation Progra Flow Chart 6

7 Transforation progra Main enu Transforation progra Paraeter Menu Paraeters for Transforation fro WGS 84 To DLTM Transforation progra Out put and File option enu DLTM Dubai Local Transverse Mercator Conclusion The optial transforation paraeter sets coputed for ain land and Dubai The full Seven paraeters set is recoended using Molodensky Badekas odel For any ellipsoidal points a conversion can be carried out up to 0 c precision, where as for any Clark880 points conversion precision between 0 50 c 7