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Land Surveyor

### Railway Alignment design, detailed topographical survey and alignment fixing

Question for the experts:

During Railway alignment and topographical survey for 260km long rail corridor , I came across a process where a survey company followed the below procedure

1. Established DGPS Stations every 5 km using whole to part concept. Total of 85 control point pairs have been established in 260km long corridor.

2. Converted the  DGPS control points coordinates to grid coordinates - UTM 44 N

3. Again converted the UTM Coordinates to modified UTM ("they are calling it Plane UTM").
Few of the coordinates are given below
1. GPS83 22° 24' 11.03540" N 82° 27' 58.76349" E UTM Coord: Easting 650935.447 Northing 2478177.945 0.000 0.000 Modified UTM : E-650935.447 N- 2478177.945
2. GPS83A 22° 24' 09.69999" N 82° 27' 59.28814" E UTM: Easting -650950.851, Northing-2478137.021 -0.002 0.004 Modified UTM: Easting-650950.853, Northing-2478137.017
3. GPS84 22° 24' 53.94240" N 82° 29' 24.71701" E UTM: Easting -653380.418, Northing-2479521.729 -0.276 -0.158 Modified UTM: Easting -653380.694, Northing- 2479521.887
4. GPS85 22° 25' 21.78230" N 82° 31' 25.31431" E UTM: Easting -656820.2538 Northing-2480412.551 -0.633 -0.241 Modified UTM: Easting -656820.8864 Northing-2480412.792

Is the term "Plane UTM" a standard term used by surveyors?For Plane UTM coordinates the UTM standard projection parameters have been tweaked;

Modified Projection Details

1 Ellipsoid WGS-84

2 Semi-major axis 6378137

3 Flattening-1/f 298.2570

4 Projection Plane UTM

5 False Easting 650935.447

6 False Northing 2478177.945

7 Latitude of Origin 22° 24' 11.03540" N

8 Central Meridian 82° 27' 58.76349" E

9 Scale factor at Origin 1.0000

10 Average Projection Scale Factor 1.00001583749

11 Average Elevation Factor 0.99996171802

12 Average Combined Factor 0.99997755494

My question is tweaking the False Easting and Flase Northing (the values belong to first DGPS Control point), a standard practice?

The project is a linear 260 km running in the direction: North East to South West.
The entire project corridor is inside UTM zone 44 N.

4. The entire control point traverse survey and detailed topographical survey was carried using Total station using Plane UTM coordinates

5. The railway alignment design was done in AutoCAD using the plane UTM coordinates.

6. The survey company didn't re-convert the plane UTM topo features coordinates and plane UTM based railway corridor coordinates (Centerline, Right and left corridor points) back to standard UTM coordinates,which was a matter of concern for me?

The survey company created KML of the designed corridor using the plane UTM coordinates , which obviously didn't show the correct location or match the google earth

Any thoughts and suggestions?

Thanks

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#### Replies

• Land Surveyor
 GPS34 21° 54' 25.75421" N 81° 12' 47.33660" E UTM E:522015.7551 UTM N:2422565.538 33.303 28.976 Plane UTM E: 521982.4518 Plane UTM N: 2422536.562 GPS34A 21° 54' 27.53950" N 81° 12' 45.37043" E 521959.2675 2422620.351 33.335 28.963 521925.9325 2422591.388 GPS33 21° 53' 19.21674" N 81° 12' 20.16987" E 521239.0464 2420518.723 33.294 29.933 521205.7523 2420488.79 GPS33A 21° 53' 19.70215" N 81° 12' 17.25569" E 521155.4045 2420533.536 33.331 29.941 521122.0739 2420503.596 GPS32 21° 51' 35.35403" N 81° 12' 08.25858" E 520901.4536 2417324.93 32.913 31.291 520868.5409 2417293.639