Convert points from grid to ground

[Anonymous]

I have a csv file with the points in grid.

I do have the scale factor of 3TM Ground = 0.999799/1.00020104

so I need to scale the points by 1.00020104 to change them to ground without changing the elevations of the points

How do I do this?

[Anonymous]

Under drawing settings there is a transformation tab. You can enter scale factor info there. Then when importing the point check the transformation option.

[Todd_Rogers]

Set your coordinate system in the Drawing Settings. While still in the Drawing Settings, click the Transformation tab. Check the box to Apply Transformation Settings. Just to the right, under Grid Scale Factor, change the Computation to User Defined. Then enter your scale factor. Now import your points. In the import points dialog box, make sure you have checked Do Coordinate Transformation if Possible.

[BushW]

Hi @Anonymous

Did @Todd_Rogers and @Anonymous resolve your issue with the great suggestions? If so, please reward the post that worked with a Kudos and pleases also mark a post or posts as Accepted Solution(s) that resolved the issue or answered your question.

Here to help and thank you for doing so.

[Anonymous]

Hi,..

Sorry the user who receive my help was logged with my subscription acount in AutoDESK
So I forgot to LogOut before leaving here machine..meanwhile, ..she ask the question on this forum under my account.
I think you can close this now, I give you kudos for your great support. 🙂
Thank you.

[Anonymous]

I did these steps, now my values for Grid NE have changed, and my NE values are the same as they were when I imported. And when I export, they are still the same NEZ as my averages grid points I imported to begin. I want my point to be in ground. What am I missing? 

[rl_jackson]

Here are they steps you need to take to accomplish your goal.

1. At the transforms tab, upper left - check apply transforms

2. Check apply see level scale factor, and then provide an average elevation for your site. (i.e. 5 in this case)

3. Grid Scale Factor: Here either use Prismoidal or you can set the to User Defined and and insert the Combined Scale Factor for your local area.

4. Local North & East, Select a point that is central to your site, preferably a control point but does not have to be.

5. Copy the Local N & E values to the Grid N & E values respectively (In this case I'm going from a assumed system to grid). Civil 3D only does a single point transform so be aware of this.

6. Do any rotation if needed (I specified my ground to grid rotation)

7. Delete the points from the drawing.

8. Re-import the points in the drawing, they will now be scaled based on the average elevation and grid scale factor.

HTH

[EVANV4NUZD]

Our survey department has been using this transformation workflow for several years now, working in the field in SPC and loading grid points into C3D through the transformation tab. It is working well except for the fact that we have not found a way to export the completed drawing in SPC. More and more of our projects require that we deliver spatially referenced drawing files and since the transformation converts grid to local coordinates and ground distance, we have lost the ability to satisfy this requirement. Has anyone solved this issue? We are currently forced to save the drawing out, then create a grid point in the local coordinate system drawing, move the drawing data to the state plane coordinate location, then rotate and scale all the data to achieve state plane. There must be a better approach to this!

Thanks!

[Pointdump]

Hi Evan,
There sure is a way. You can create an Affine Post-Processor Coordinate System like >>>This<<< and use the >>>Coordinate System Transformation Tool<<<. The beauty part is that you can work in your ground system, even adding GIS data, like shapefiles. Then use the Transformation Tool to ship it off in State Plane.
Dave

[EVANV4NUZD]

When I try to follow the instructions below, there is no option for Drawing Transformations. My drawing is in local coordinates and ground distances but Grid SPC data was imported through a transformation to achieve this. If I look at the points, they all are listed with both local and SPC coordinates. Why would I not see this option in toolspace?

Thanks!

"In Toolspace, on the Toolbox tab, expand Miscellaneous Utilities 

Drawing Transformations and double-click Coordinate System Transformation.

The Coordinate System Transformation dialog box opens showing the current coordinate system."

[Pointdump]

Evan,
The Transformation Tool is a separate install. Go to your account page. The Tool is available for, I think, 2022 and 2023.
Dave

[EVANV4NUZD]

Thanks for your help with this. After watching a video about the use of the coordinate transformation tool, it looks like it would provide the functionality that we are missing. Can you confirm that it will convert the whole drawing including survey figures, points, surface, annotation etc. Also, I would like to confirm that this will work for situations where the drawing is linked to state plane with a transformation but the active drawing is in an assumed local coordinate system. 

Thanks!

[Pointdump]

Evan,
I haven't tested the Transformation Tool on Survey Figures or Annotation. Works on everything else.
Your local coordinate system will need to be defined in MAPCSLIBRARY. That's where the Custom Affine Projection comes into play.
Dave

[AllenJessup]

I believe that it will transform most everything. Can't say it's absolutely everything. Take a look at THIS.