C3D-COORDINATE TRANSFORMATION

[CADEngr2014]

Hello,

I am using Civil 3D 2015.

I have attempted my first coordinate transformation as a training exercise.  My intention is to transform from a state plane grid to ground coordinate.  My work flow is this: In the Drawing Settings I set the file coordinate (I understand is the source coordinate) which is State Plane North Carolina, NAD83, US Feet.  In the Transformation tab I set a base point number and its Grid Northing and Grid Easting as displayed in the Prospector tab.  For the Grid Scale Factor I am using the Reference Point which calculates to 1.00001184 (for now since do not have an OPUS report, etc).  I have a few questions based on the above workflow: Is the scale factor greater than 1 that places the transformation in the direction intended (from grid to ground)? The scale factor C3D provided must be the scale between the Local N-E and the Grid N-E of the base point?  Why do I have to provide the Grid N-E while I do not have to provide the local N-E in the dialog?

[Pointdump]

CE,

"Is the scale factor greater than 1 that places the transformation in the direction intended
(from grid to ground)?"
Generally, less than 1. The Combined Scale Factor needed for Ground to Grid Transformation will generally be greater than 1.

"The scale factor C3D provided must be the scale between the Local N-E and the Grid N-E of
the base point?"
The Geodetic Calculator gives you the Grid Scale Factor, which is only part of the Combined Factor you need.

Elevation Factor = 20,906,000/(Ellipsoid Height + 20,906,000)

Grid Scale Factor X Elevation Factor = Combined Factor

"Why do I have to provide the Grid N-E while I do not have to provide the local N-E in the
dialog?"

Can you elaborate on that?

Dave

[CADEngr2014]

Dave,

The attached image shows the Grid Coordinates that I typed-in for a transformation.  At least that is what the videos showed for transforming between grid and ground.

[Pointdump · Accepted solution]

CE,

If you set your Grid Northings and Grid Eastings to the same as your Local Northings and Local Eastings, the only thing you'll do is Scale (1.00001184392733) and Rotate (0.49059471684d) your points. Don't use Reference Point for the Grid Scale Factor. User-Defined is what you want. The Scale Factor listed in the Geodetic Calculator is Grid Scale, and you want Combined Factor, so you'll need to multiply the Grid Scale Factor by the Elevation Factor to get it. Do you have the Ellipsoid Height for that point? For the Grid Rotation Angle you'll put in the Convergence (Difference between Grid North and True(Geodetic) North).

Dave

[Pointdump]

CE,

Oh, and also:

For Ground to Grid, use the Combined Factor. For Grid to Ground, use the Reciprocal of the Combined Factor.

For Grid Rotation Angle, change the sign (+/-) on the Convergence listed in the Geodetic Calculator.

Dave

[ren26_1984]

hola: soy de peru,

hace un tiempo lleve un curso de trsnformacion de coordenatas utm a topograficas y utilizamos un par de softwares y en ambos siempre se carga un geoide para la transformacion, en cambio en el civil 3d no se puede caragar ningun geoide para dichas transformaciones, y con los dos sofwares en resultado es el mismo mientras que con el civil 3d varia, por eso se puede decir que civil 3d no hace transformaciones.

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@Pointdump wrote:

CE,

Oh, and also:

For Ground to Grid, use the Combined Factor. For Grid to Ground, use the Reciprocal of the Combined Factor.

For Grid Rotation Angle, change the sign (+/-) on the Convergence listed in the Geodetic Calculator.

Dave

---

[Pointdump]

Ren,

Civil 3D no considera el geoide, como Trimble Business Center hace.

Es mejor dejar sus coordenadas en UTM.

Dave

[ren26_1984]

buenas noches:


si civil 3d no considera el geoide para transformacion, entonces civil 3d no hace transformaciones de utm a topograficas y viceversa.




y si es necesario transformar de utm a topograficas y viceversa.



saludos.


RRCH.

[Pointdump]

Ren,

Sí. Si agrega Trimble Link a C3d se puede "instalar" un modelo de geoide, pero no creo C3D lo usa para otra cosa que pasarlo a un recopilador de datos nada. Yo no creo que tenga ningún efecto sobre elevaciones.

Yes. If you add Trimble Link to C3D you can "Install" a Geoid Model, but I don't think C3D uses it for anything other than passing it on to a Data Collector. I don't think it has any effect on elevations.

Dave

[CADEngr2014]

Ren26_,1984,

Sorry but I do not read or speak spanish.  If you can translate, that would be very helpful.

[Pointdump · Accepted solution]

CE,

Me either. I use Google Translate for anything other than English. Works great.

Dave

[CADEngr2014]

PointDump,

Thanks for that tip, I will give it a try, very interesting.