Scale contours from ground to grid

[jessi.pietrovito]

I have a original ground dwg with contours in Ground coordinates

I have another dwg with my imported Lidar which is in Grid coordinates. I need to import the OG contours but change them to grid.

How do I do this so it changes the x and y but not the z. Every time I try to scale the block it changes the z factor as well.

[Mike.M.Carlson]

Hi there-

You will need to get the Combined Scale Factor from your surveyor.  You should get a Ground to Grid scale factor (something like 0.99999xx).  You will also have to get the Control Point or Benchmark coordinates the Surveyor used to Scale from GRID to GROUND in both State Plane Coordinates and Ground Coordinates.  Once you get this, you can create little circle objects (GRID and GROUND northing and easting) that are set at elevation zero in both drawings.  You will then have to attach the OG (GROUND) as an XREF into the GRID dwg.  It is easier to just attach the XREF at first and then use move command to translate the XREF into position.  The Move Base point will be the Ground Circle object (use OSNAPs Center of Circle) and then Move the XREF from this base point to the GRID Circle object.  Then under XREF Properties Scale the XREF by the GROUND to GRID SCALE Factor the Surveyor gives you.  There may be a rotation too, but he or she will tell you that.

There is also an option via the Survey Database and setting up your Ground dwg Drawing\Settings\Transformation Tab, but that works best for Points and Survey Figures, but in your case, you have too much geometry to manage via Survey Data Base...unless your Surveyor gives you the ground points in which case you leverage the Survey Database to do this conversion and rebuild the OG surface.  Cool having it set up this way because you can drag and drop back and forth between GRID and GROUND and vice versa.   I can assist with that if you want.

I hope this helps.

[jrauch]

I'm not gonna suggest you do this... I second the recommendation to contact a surveyor. But from an AutoCAD perspective, when you insert a block, you can set the X-, Y-, and Z-scale factors independently in the insert command dialog, or after inserting the block, you can use the properties dialog to modify the scale factors (assuming you didn't explode the block).

[BushW]

Hello @jrauch

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@Anonymous wrote:

But from an AutoCAD perspective, when you insert a block, you can set the X-, Y-, and Z-scale factors independently in the insert command dialog, or after inserting the block, you can use the properties dialog to modify the scale factors (assuming you didn't explode the block).

---

That is correct but, you can also use the scale command as well if you don't explode the block. It shouldn't change the Z value. Is that happening?

Wendell

[jessi.pietrovito · Accepted solution]

If I go scale then select 0,0,0 as base point then I usually put in the scale factor it did change the z elevation.

I ended up using this lisp called scale map and it seems to work good.
you have to convert the polylines by using the command convert poly - choose heavy - and then select the contours
then appload the lisp : scalemap

then type the command scale map and put in the scale factor

This seems to work to convert the contours to grid but keeping the elevations.

[BushW]

Hello @jessi.pietrovito

I am happy to hear that you found a solution! If you ever have any problems in the future, I'll be here, and I'm glad to help.

Best Regards,

Wendell

[Anonymous]

Where did you get the scalemap.lsp from ? Can you post a link or site.

I could really use this and others for sure.

Thanks, Dennis

[jessi.pietrovito]

Here is the LSP file

[Pointdump]

Jessi,

I'm not a big fan of Scaling. I prefer to use a Custom Low-Distortion Projection. That way you can move seamlessly between Ground(Local) and Grid.

Here's a well-explained workflow:
<<<Part 1>>>
<<<Part 2>>>

Dave

[croberts83364]

"If I go scale then select 0,0,0 as base point then I usually put in the scale factor it did change the z elevation."

Don't put in the 3rd 0.  Try just 0,0

If that does not work and it is still a block then you can change the x,y scale values in the property box and leave the z scale 1

[croberts83364]

Excellent find Dave. I post under many different names on here but I always love your posts and they are always super helpful. You are king of coordinate issues.

I am having an issue however in that TX83-SCF is not "Transverse Mercator" as is the one in the tutorial and there is no "Scale Reduction" box available. Do you have any thoughts on how to proceed?

[Mike.M.Carlson]

Hi @Pointdump ,

This workflow works great.  What about instances where you have a user-defined ground system (not a modified state plane) with a rotation component?  We come across this all the time where a facility may be on a "Plant Grid" with legacy control based on simple 10000, 5000 coordinates for example, but it is a ground system.  Typically a PLS will locate 2 legacy control points on Site:

1 point will serve as the published state plane (Grid) tie base point and we are provided with the combined scale factor to reduce down to grid

We also have a 2nd point which serves as a rotation point that has local and GRID values. This point as you know would be used to determine the azimuth of this Plant Grid.

We then use the C3D Transformation tab to put in the base point and rotation point and CSF here: 

In this case where there is rotation, you can't define a custom LDP?  Curious your thoughts on this where rotation is concerned.

Many thanks Dave!

[Pointdump]

Hi Cody,
EPSG:2278, Texas South Central (ftUS), is a Lambert Conformal Conic with 2 Standard Parallels. You're right that it can't be scaled like the Transverse Mercator example in the video. The 2 Standard Parallels set the scale of TX83-SCF.
For a Lambert Conformal Conic Coordinate System you can create a Custom Affine Projection. Alan Gilbert explains how >>>Here<<<. Unfortunately, Alan just shows a translation, not scale and rotation. So to get all the parameters; A0, A1, A2, B0, B1, and B2, you'll need to use Brad's method >>>Here<<< or use a little Matrix Algebra in Excel, like I did >>>Here<<<. You'll need a minimum of 3 "match-up" points.
Dave

[Pointdump]

Hi Mike,
The Transformation Tab has a big defect. Map commands don't work. A glaring example is that the T Tab breaks Bing Live Maps. A Low-Distortion Project works good, but requires a LOT of thought to set it up right, and yes, rotation is a problem. A custom Affine Projection is the easiest way I've found to work seamlessly between Grid and Ground. Scale and Rotation are no problem, and you can drag-n-drop in GIS data.
Attached is an Excel spreadsheet that calcs the A0, A1, A2, B0, B1, and B2 parameters for a site in Temecula, California. Those parameters allow you to use >>>Alan's method<<<.
I would love to demonstrate this on one of your Plant Grid projects.
Dave

[Mike.M.Carlson]

Thanks so much Dave!  I would love to see your workflow from A to Z.  I have attached a base .dwg based on Plant Grid (ground).  The Cover Sheet Tab has the Site Specific CSF and South Carolina to Plant Grid coordinate tables:

There is a slight rotation  from plant north to SPC83 North:

Matrix calcs are my weak area, so keep that in mind 🙂  

Thank you sir.

Mike

[Pointdump]

Thanks for the drawing Mike. I'm on it. Results with workflow tomorrow afternoon.

Dave

[Mike.M.Carlson]

You're a good man Dave...I owe you a beer.  In Henderson next week (Wed/Thurs) if you want to grab a pint as a thank you!

[Pointdump · Accepted solution]

Mike,
OK, here's the workflow.
Assign 23021T02-PhotoScience.dwg EPSG:3656, NSRS07.SCIF. (From Cover Layout)
Import the 12 control points referenced to NSRS07.SCIF.
Find 3 points that represent the extents of the drawing. I used:

550868.881,2497843.505,WGS-1
548414.345,2505539.589,WGS-6
543976.047,2503494.935,WGS-7

In Excel, plug in the 3 match-up points. See the attached 3656_to_PlantGrid.xlsx.
I learned how to do this from Egor Grebenyuk's AKN article >>>Here<<<.
Duplicate, then Edit, Coordinate System NSRS07.SCIF, using Alan Gilbert's video >>>Here<<<. Your parameters will be:

A0 -2399289.754
A1 0.989845868
A2 -0.142144199

B0 -899535.7992
B1 0.142144229
B2 0.98984571

I named the new Coordinate System "NSRS07.SCIF-PlantGrid".
There are 2 ways to convert your 23021T02-PhotoScience.dwg:
1. Attach/Query into a new drawing assigned NSRS07.SCIF-PlantGrid.
2. Use the new >>>Transformation Tool<<<.
One thing I left out, before creating the new coordinate system go to Drawing Settings >> Ambient Settings >> Lat Long >> Format: Decimal and bump up Precision to 8.
I tested by importing both sets of 12 control points. They matched up. And the project looks like where it should belong in Bing Live Maps.
Dave

[Mike.M.Carlson]

Hey Dave,

This worked great.  Many thanks!  This will come in handy for me on several projects. 

I also tried this method to determine Coordinates based on California Spatial Reference System which is on a later epoch (2017.5).  I chose a few SOPAC CORS that were in a Triangle pattern around my UAV test Site (here in SoCal-pink circles below) with good CSRS 2017.5 epoch CA 6 control burned on-Site relative to network adjusted ties to these same 3 CORS (2 ties w/ 1 as a check). 

I then used HTDP to transform between Reference Frame epochs to get to NAD83 2010.00 epoch lat/long/heights for these CORS and used Trimble Business Center to help me use the standard CA zone 6 map projection / Geoid 18 parameters to get my NEZ values for the spreadsheet you sent.

I followed Alan's video and created a coordinate system in C3D.  At this point I had 1 dwg with 2017.5 control and one with 2010.00 epoch control.  I drew colored lines connecting the on-site control in each. 

I then created new dwg, assigned new coordinate system (CSRS2017.5.CAVIF), and imported my .csv with control points in terms of CSRS2017.5.

Then I used MapExplorer to attach to the 2010.00 epoch dwg.  I then queried all objects and checked the linework vs. imported cogo points and only see about <0.01' at all points.

Pretty good result for only 3 matrix parameters based on CORS ~8-10 miles from Site don't you think?  Can I improve on this at all using more than 3 matrix points somehow?      

Thanks again for your wisdom sir.

[Pointdump]

Mike,
Better than <0.01'? I don't think so.
The matrix algebra method with Excel is limited to 3 match-ups. 4 points would produce 8 parameters, 5 points would give you 10 parameters, etc.
But there's another way, using QGIS. Brad shows the way >>>Here<<<. I haven't tried it yet, but with your excellent data I think I will tomorrow.
Dave