topic Re: adding a new coordinate system into the library in Civil 3D Forum

adding a new coordinate system into the library

jefflambert9091 — Wed, 22 May 2024 17:11:48 GMT

Ohio's DOT has a Ohio County Coordinate System: The Ohio County Coordinate System (OCCS) is a set of conformal map projections designed by ODOT’s Office of CADD and Mapping Services to provide a series of low distortion projections for the use of Ohio stakeholders. I have their projection files for each county. I would like to add some of them to the Coordinate system library. I searched and see how to manage and create, but was hoping there was a way just to add it or do I need to go through the create. We try steer clear of adding systems and confusion for all involved, but we were given a project in this system. I want to be ability to transform/link to other GIS data.

Re: adding a new coordinate system into the library

Pointdump — Wed, 22 May 2024 17:28:25 GMT

Hi Jeff,
Yes, it would be nice if you could bulk-load all 88 of those LDP's. But no, you'll have to add them one at a time with MAPCSCREATE. Have you checked C3D 2025? Autodesk is pretty good about adding coordinate systems to MAPCSLIBRARY.
Dave

Re: adding a new coordinate system into the library

Pointdump — Wed, 22 May 2024 19:42:11 GMT

Jeff,
The new Ohio projections are eazy peazy to create. Be glad you're not in Minnesota. Each new Minnesota projection requires creating a new datum based on a custom ellipsoid, instead of just scaling NAD83:
semi-major_axis = a = 6378137.000 + ellipsoid_height
Dave

Re: adding a new coordinate system into the library

jefflambert9091 — Wed, 22 May 2024 20:18:58 GMT

Thanks Dave, I was pretty sure that I would be getting a response on this from you. 🙂 I have never created one so I will have to dig in. Luckily, we will only ever need a few. I hope. Plan on staying in NAD83 State Plane till the new Datum comes out.

Re: adding a new coordinate system into the library

Pointdump — Thu, 23 May 2024 16:42:48 GMT

Jeff,
There's 2 ways to create a new coordinate system. You can Duplicate, then Edit, an existing similar coordinate system. Or you can create one from scratch with command MAPCSCREATE, which walks you through with a wizard. Either way, before starting, you'll want to do a few things. In UNITS set highest precision. In Ambient Settings set Lat Long to Decimal and bump precision up to 8. Bump Coordinates precision up to 8. And then figure out the extents of your new projection. You can drag-n-drop a shapefile of a county into a drawing and use MAPTRACKCS to give you some numbers.
Here's a few screen shots of creating a custom projection for Cuyahoga County, where I was born.
Dave

Re: adding a new coordinate system into the library

jefflambert9091 — Thu, 23 May 2024 18:16:11 GMT

Thanks for the tips! I will let you know how it turns out.

Re: adding a new coordinate system into the library

Cadguru42 — Mon, 01 Jul 2024 15:35:34 GMT

I'm having to do just this on a project, but Ohio has decided to make things very complicated. @Pointdump should appreciate this. The new project has been surveyed in Cuyahoga County's new LDP system, so I have to create a new coordinate system for it. But the surveyor (they won't tell me who) provided a C3D drawing that has the C3D unit set to US Survey Feet, no coordinate system, and the AutoCAD unit set to Feet (International Feet). So I start asking questions about why the ACAD unit doesn't match the C3D unit and what coordinate system was used to create the survey. The surveyor's response (2nd hand) said "It's in feet. Not international feet nor US survey feet." Is there a 3rd foot unit definition that I'm not aware of?

I'm going to create a new coordinate system for this and the surveyor insists that he shot everything in US survey feet even though the ACAD unit was International Feet.

So, two things.
1. Assuming the points and figures are placed correctly in the model space to match the CS, I should be able to just add the new coordinate system and set the ACAD unit to US Survey Foot and be good to go, correct?
2. If the NGS dictates that all of the new state planes are to use International Foot, why is Ohio using US Survey foot?

Re: adding a new coordinate system into the library

jefflambert9091 — Mon, 01 Jul 2024 15:58:36 GMT

As to Ohio, I stay away from the new systems and have not dug into them. This thread being the reason. This keeps the foot, international foot and survey foot out of the game. I stay with OH83-SF. Just took this by Jeff Jalbrzikowski who is the Appalachian Regional Advisor at NOAA National Geodetic Survey. "History and Retirement of the U.S. Survey Foot". It is retired but he says do nothing but prepare until the new system (SPCS2022) comes out. We already have enough systems out there, so our philosophy is to stick with what we can and not keep changing systems that only adds another step to the confusion. I was hoping to retire before SPCS2022 comes out, but it's looking like dealing with this and integrating it into our processes will be my last venture.

Re: adding a new coordinate system into the library

Pointdump — Mon, 01 Jul 2024 17:20:09 GMT

"It's in feet. Not international feet nor US survey feet." Is there a 3rd foot unit definition that I'm not aware of?
Maybe Left Feet? LOL
"I should be able to just add the new coordinate system and set the ACAD unit to US Survey Foot and be good to go, correct?"
Should work. You'll definitely want to check a few NGS Control Points. The difference between the two units would be glaring.
"...why is Ohio using US Survey foot?"
I wondered about that myself.
Dave