topic Re: Rotate and Scale UTM-10N to Local Coordinate system in Civil 3D Forum

Rotate and Scale UTM-10N to Local Coordinate system

jacob.chadima — Mon, 12 Apr 2021 23:38:47 GMT

I have a drawing that is set in a local coordinate system. I am trying to import it into Infraworks to get some 3d models out of it. I need to create a custom coordinate system based on NAD83 UTM-10N that Infraworks will recognize. I am trying to figure out how I can scale and rotate about a certain point to achieve the correct transformation. When I look at the transform tab, I am only able to change the northing and easting. I also need the transformation to be applied in a certain order.

The order of operations is as follows:

UTM to Local:

1. Move UTM: N5451671.853 E507749.107 to Local N5451470.929 507848.580 (this part I can do with the transform tab under drawing settings)

2. Scale by 1.00039416330349 about 507848.580,5451470.929,

3. Rotate 00D00'00.27422" about 507848.580,5451470.929

I have not been able to find a way to do transformation steps 2 and 3.

Is it possible to perform this kind of transformation?

Re: Rotate and Scale UTM-10N to Local Coordinate system

andrewofabley — Tue, 13 Apr 2021 01:08:05 GMT

@jacob.chadima

So, in essence you want to reproject your data to a different coordinate system?

Re: Rotate and Scale UTM-10N to Local Coordinate system

rl_jackson — Tue, 13 Apr 2021 02:45:12 GMT

The transform tab does all of that.

For the scale, select the check box at the upper left part of the dialogue box, that refers to Sea Level.... This is how you can set your Scale Factor as it opens that part. (Note: the scale factor is based on a average elevation for the site, so look at that across your site area.)

At the bottom right, is where you can adjust the rotation, by your prescribed angle

C3D only does single point transforms, so what your trying to do it's set up for. This should get you in the ballpark.

Re: Rotate and Scale UTM-10N to Local Coordinate system

Pointdump — Tue, 13 Apr 2021 09:13:39 GMT

Hi Jacob,
The Transformation Tab breaks Bing Live Maps and can't use Map Functions to bring in GIS Data. I'd like to propose a different tack. You can use a Custom Transverse Mercator with Affine Post-Processor to work seamlessly between your Local Coordinate System and UTM83-10. All you need is 3 points around your area of interest where you can match up Local/UTM Coordinates, like this:

Dave

Re: Rotate and Scale UTM-10N to Local Coordinate system

rl_jackson — Tue, 13 Apr 2021 10:50:12 GMT

Dave,

I've personally not had an issue with Bing Live maps or using FDO from Map3D for Images while using the transforms tab, the images actually rotate slightly, based on the north angle rotation. Although the Custom System does solve the problem as well.

Re: Rotate and Scale UTM-10N to Local Coordinate system

Pointdump — Tue, 13 Apr 2021 13:53:24 GMT

Hi Rick,
To demonstrate, the first pic is straight UTM83-10 with N5451671.853, E507749.107. Pics 2 & 3 are with Transformation Tab using Local and Grid one way, pics 4 & 5 the other way. (I've never figured out what the T-Tab means by "Local" and "Grid".) Note where the same point shows up in the 3 scenarios.
Dave

Re: Rotate and Scale UTM-10N to Local Coordinate system

Pointdump — Tue, 13 Apr 2021 13:58:28 GMT

Jacob,
I haven't done much with Infraworks, so I'm not familiar with assigning a coordinate system, but I don't think the Transformation Tab settings will carry over to Infraworks. You'll probably need a Custom Map Projection. Does Infraworks use the same MAPCSLIBRARY that Civil 3D uses?
Dave

Re: Rotate and Scale UTM-10N to Local Coordinate system

jacob.chadima — Tue, 13 Apr 2021 16:34:31 GMT

How can I set the point of rotation? I don't really understand the Local and grid Northing/easting. That sets up two points and doesn't specify an angle. Specifying a grid rotation angle has two angles, but no point to rotate around.

Re: Rotate and Scale UTM-10N to Local Coordinate system

jacob.chadima — Tue, 13 Apr 2021 18:01:22 GMT

Hi Dave,

I would like to try out your solution. I think it will be better because I can then use this new coordinate system in infraworks too. How would I go about using a Transverse Mercator with Affine Post-Processor to specify the three points? When I create a new coordinate system I get a a window that shows inputs for a central meridian and several coefficients. I'm pretty new to this so I'm not sure what exactly to do here. Could you walk me through it or point me towards some reference material?

Thanks!

Re: Rotate and Scale UTM-10N to Local Coordinate system

Pointdump — Tue, 13 Apr 2021 20:12:51 GMT

Jacob,
I was hoping you'd ask. Those coefficients are obtained by a little matrix algebra, made easy by Excel. I'm attaching an xlsx file to show you how to plug your 3 points in.
Dave

Re: Rotate and Scale UTM-10N to Local Coordinate system

Pointdump — Tue, 13 Apr 2021 20:23:20 GMT

Jacob,
And to elaborate on creating your custom coordinate system, in MAPCSLIBRARY make a duplicate of UTM83-10 and then edit the duplicate.
Dave

Re: Rotate and Scale UTM-10N to Local Coordinate system

jacob.chadima — Tue, 13 Apr 2021 22:59:37 GMT

Thanks for the spreadsheet. I'm trying to work through it. What is the HARN/CA.CA-IF? And what is the difference between that and Ground Easting/North. Am I correct to assume the "Ground Northing/Easting" is the local coordinate system?

Also, what is the difference between UTM83-10 and CSRS.UTM-10N?

Re: Rotate and Scale UTM-10N to Local Coordinate system

Pointdump — Tue, 13 Apr 2021 23:14:41 GMT

That spreadsheet is just one example of the math involved. I've experimented with about a dozen of these.

"Am I correct to assume the "Ground Northing/Easting" is the local coordinate system?"
Yes, exactly.

"Also, what is the difference between UTM83-10 and CSRS.UTM-10N?"
CSRS is the Canadian version of NAD83. It's not a straight transformation. It uses GSB files. It varies all over Canada. I've seen differences up to 70 Meters.

Dave

Re: Rotate and Scale UTM-10N to Local Coordinate system

Pointdump — Tue, 13 Apr 2021 23:26:53 GMT

I just remembered, to find the difference between the NAD83 and CSRS Datums, look >>>Here<<<.
Dave

Re: Rotate and Scale UTM-10N to Local Coordinate system

Pointdump — Wed, 14 Apr 2021 00:11:31 GMT

Dang, I just checked and the TRX site doesn't have NAD83 anymore to compare. Just CSRS. So using the TransferPoints Function and comparing the difference I get a distance of 97.4 Meters between the 2 Datums.

Re: Rotate and Scale UTM-10N to Local Coordinate system

Pointdump — Wed, 14 Apr 2021 01:35:36 GMT

Oopsie, my bad. I forgot to add the British Columbia GSB file to the NAD83_to_CSRS Geodetic Transformation. Without that GSB file it's transforming between NAD27 and CSRS. So it's not 97.4 Meters. It's only 0.05 Meters.
Be sure you've added the GSB files for any Province you might use. You can find them here:
https://webapp.geod.nrcan.gc.ca/geod/data-donnees/transformations.php

You might have to create a (free) account to access.

Re: Rotate and Scale UTM-10N to Local Coordinate system

ChicagoLooper — Wed, 14 Apr 2021 05:55:33 GMT

Heres' video which demonstrates how to apply a transformation to a drawing that has a known coordinate system. Given two points: a known point within your grid and a reference point, the transformation can be applied. If you need to scale, you'll need a basepoint and the scale factor. If you need to rotate, you'll need a basepoint and the rotation angle.

<<The 'known point', the reference point, the basepoints, scale factor and rotation angle, were all taken from the parameters in Post #1 of this thread.>>

To view the video, you may click >>HERE<<.

Re: Rotate and Scale UTM-10N to Local Coordinate system

Pointdump — Wed, 14 Apr 2021 08:51:30 GMT

Jacob,
I found the >>>Canadian Transformation Site<<< that will give you the shift between NAD83 and CSRS.
Dave

Re: Rotate and Scale UTM-10N to Local Coordinate system

Pointdump — Wed, 14 Apr 2021 11:59:26 GMT

Jacob,
Had some time this morning, so here's what I did. I drew a big triangle around your UTM: N5451671.853 E507749.107 Point. (I used CSRS.UTM-10N) Then I translated, scaled, and rotated the triangle as per your specs. (And the order of your specs) I plugged the 3 correlated points into the attached spreadsheet to get the affine coefficients. Then I used those to create an Affine Coordinate System in your Local numbers. See if this is close to what you want. Of course you'll want to plug in your own numbers by selecting 3 points on the outside edge of your project area.
Dave

Re: Rotate and Scale UTM-10N to Local Coordinate system

jacob.chadima — Wed, 14 Apr 2021 23:25:34 GMT

Thanks Dave. I have my 3 points with their northings and eastings, but I'm just unsure of how to enter them into the spreadsheet. The first two columns are "HARN/CA.CA-IF Easting" and "HARN/CA.CA-IF Northing". I'm assuming that HARN/CA.CA is some kind of datum and you subtract the northing and easting of each of your 3 Grid coordinates. I want to try and understand this spreadsheet before I just blindly start punching in numbers.