Surface Data References and Civil 3D

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We’ve discussed the topic of Data References (DREF) in Autodesk Civil 3D and the important Object Model challenges we simply have to deal with in our Civil 3D projects. This DREF chatter spawns a bunch of questions about Civil 3D Surfaces, Surface DREFs, and how to make them work better and faster. The existing and design surface discussion takes a few words and a couple of videos to get through. Enjoy.

What’s Wrong with this Picture?

Someone sent me a picture of a complex Surface Edit stack with lots and lots of entries. Yuck.
There is a Point Group; a couple of Paste operations; lots of Add Breaklines intermixed with tons of Delete Lines, and a good number of Swap Edge entries. There is no surface Boundary in the Surface Edit stack.

Surface Edit Stack Soup

Suddenly somewhere in this Surface Edit soup there is a bad 0,0,0 entry. How to find it?

In Civil 3D, it is easy enough to turn off the input data sources until you find where the bad data is coming from. Yes, you can do that in the Surface Edit Stack. We can temporarily turn off entries, rebuild, and check the newly resolved data. We can also do that in the Surface Build Properties which might be faster but isn’t exactly the same thing. When and how we need to be granular matters.

Train the Autopilot or Work Harder

Check the newly resolved surface data?

I am not talking about looking at the surface on the screen (it could be invisible) but at the Surface Properties themselves. You go to and review the Surface Properties Statistics tab every time for every surface, don’t you? Sound silly?

Trust me. Go to the Surface Properties Statistics tab. Look and count to 3. Move on. Bet this tip saves your bacon sooner rather than later. Your brain sees more than you do. Sneaky Surface problems tend to leap out and poke you in the eye if you give that brain a chance. If we don’t, we cry more often.

Do Your DREF Surfaces Look Like That?

The odds are these folks employ the old school approach to surface building. You know the drill.
Vomit up all the juicy survey bits and stir them around a bunch until the pool of vomit looks good enough.
I hate to say it…
If you have Surface DREFs with this kind of content in them, that’s probably what you do.

It’s effortless to confuse accuracy and precision with suitability.

The formal definition of a Surface model (or TIN) did not change in Civil 3D. Autodesk didn’t make the surface model definition and rules. That’s a public domain topology definition that Autodesk obeys. All those many Toolspace Surface Definitions are coded, fast-track methods to get to the same place. The surface model rules apply.

How we get to the Surface model end results did change and did so significantly in Civil 3D. This how and the methods to do that continue to evolve in Civil 3D. That evolution is way too easy to miss when we are ruled by old habits.

A Point Group?

The simple fact that you’d have a Point Group (based on drawing COGO points) in a published DREF Surface tells me that you enjoy pain, suffering, and punishment almost as much the Marquis de Sade. Maybe I can interest you in a copy of Mao’s little Red Book or some other painful pieces of historical fiction? Please, excuse me as I plagiarize and employ George Orwell albeit somewhat in vain…

All points that go into a Surface are not created equal.

In a benchmarked surface a surface points source should be an external Point File that can be changed and updated but is never dynamic. Does that Point File need to include the breakline (Figure) point data?

These Civil 3D Truths Are Not Self Evident

In Civil 3D TIN surfaces the surface points (not necessarily Civil 3D points) are the surface model point data (X,Y,Z) and the breaklines (X,Y,Z and X,Y,Z pairs) are Edits to the surface point data.

Surface points Rule and breaklines Edit.

The Figures (breaklines) are the predominate driver and/or QAQC problem of the man-made and natural structures that are shot out there in the field, stream, or street.

Harder to Edit Surfaces

These truths mean that a Surface made up of nothing but densely packed breaklines is pretty difficult to edit and change. Some paranoid folks ask if you can use this to protect surfaces. Yeah, you get it. Those TIN triangles can become densely packed breaklines.

Most of my experience with existing surface building involves lots of Figures (breaklines) and large datasets of points. Therefore, I tend to be very QAQC centric, process oriented, and preach that. Sometimes that can be overkill, but it is consistent, and it works in any sized dataset.


Survey Query Powers to Surfaces

This video done back in Civil 3D 2017 is used here to make the point that this Survey Query to Surfaces workflow has been functional for many Civil 3D releases. The tools have actually improved.

I employ pre-built canned Survey Queries to QAQC the Figures and Survey Points to prepare the parts that go into published surfaces properly. Many people ignore the Survey Queries thing because it is nothing like the old school vomit approach and mechanics. It also takes a bit more up-front preparation and resource management work – You must make the Survey Queries at least one time.

Survey Queries pay off in survey after survey and in surface after surface. The many and diverse canned ones we supply in the Framework for Civil 3D are easy to edit with search and replace with your Survey Codes. A lot of the up-front work is mostly done. Yes. There are even videos how to use, manage, and store them. Imagine that.
See our infamous Civil 3D Survey at Jump Speed page.
Register and visit the Documentation and Help pages for a whole lot more.

Basically, you soon discover that the order of the Queried Survey Db data into surfaces gets to be very predictable. You even get to choose whether do things inside out or outside in for example. Since the order of entry of data by type into a Surface is important, this Survey Query capability helps with the Surface QAQC a lot.

The fact that you can test parts of the Survey Db data as independent surfaces with this approach is more than useful.


Get the Data Prepared to Build a Suitable Surface

I employ benchmark versions of surfaces to check the work and to compare the progress of the work with earlier versions with Civil 3D differential surfaces. Civil 3D Surface analysis Style visuals make some hard to see problems jump out at you.

“Did I add all the breaklines everywhere or forget a couple?”

Zero elevations and some other issues obviously leap out at you. We only must always remember to look.

The Surfaces Rule of Thumb for the Not So Dumb

Always look at every surface with at least three different Civil 3D Style tools and
Contours never count.

Get Pasted

Technically, I have no problem with Paste. It does tend to separate the surface data into piles which can make the QAQC easier.

Honestly, I rarely employ Paste in final existing surfaces probably because I rely much more on Survey Dbs to edit, hold, and track changes. An existing surface is the output of a QAQC’d Survey Db.

More than one Survey Db as sources doesn’t bother me. I practiced a lot and know why and how the order of data entrance into a surface matters. I also understand that managing multiple Survey Dbs isn’t everyone’s cup of tea or where you want to start.

I recognize most/many Civil 3D users avoid work in Survey Dbs. Design folks this means you.
We are more familiar with Surfaces and fixing them.
Like I said we tend to prefer the vomit it all in and clean up the chunks approach.
The reason we did the survey was/is a surface?
We want to get on with it and tend then to suffer the consequences.
Sometimes you win. All too often you lose.
You choose…

That Big Surface Edit Stack

A large Surface Edit stack is always problematic to backtrack and audit. Knowing how to edit, reorder, and employ the Surface Edit stack is a mission critical set of Civil 3D Surface build and maintenance skills.

I’d guess that many of Delete Lines in that aforementioned stack are the result of not knowing how to make a decent outer boundary ASAP with the help of adjusting the surface Build properties. See the first video above.

In other words, you build a quick and dirty surface to construct a better outer boundary and there are Delete Lines in that surface, but the externalized boundary object is the result you want. You may repeat that process to fine tune the resultant boundary and/or boundaries. No boundaries in a Surface Edit stack is often a dead giveaway someone doesn’t understand surface models all that well.

When you Paste, do you take the time to create a new Boundary for the composite? Sometimes this matters. Sometimes the Paste is all internal to a surface with an existing Boundary.

Aside from that…

If I see a lot of Swap lines, Delete lines, and Delete or Add Points, I’d guess that folks are not using Figure Supplementing and Weeding factors well to meet an established surface specification.
Do you trust manual surface edits or automatically interpolated data more?
Which is more consistently repeatable?
I tend to choose to add Figures (and Points) rather than Swap or Delete lines in surfaces. These are easier to build, edit, and audit in the Survey Db(s) and external files.

Sadly, manual Figure creation is almost as weird as Figure Edits in the Civil 3D interface. Get over it.

Feature Lines are more intuitive to build and edit for many old school CAD folk, but harder to make into Figures than the other way around. Feature Lines do make handy surface breakline sources. Do you and your Civil 3D users know how to export Feature Lines and move them around from drawing to drawing in a project? More than a few folks out there learned to employ canned Feature Line based blocks.

External Feature Lines Just Got Easier

An easier to use Feature Line Export/Import to and from LandXML is now included in Civil 3D 2020.1+. You must wonder why? Autodesk infers this is all about the better ESRI integrations. They cannot fool me.

We really don’t want any Surface Edit stack at all in a published Surface DREF in the first place. People might get the bad idea it is OK to go in and change the surface data in it. We need systematic QAQC control and data feedback loops built into our project workflows for many reasons.

The Best Publish DREF Surfaces Are LandXML Based

Every published DREF surface should have nothing but a LandXML file data source. Like the Point File data mentioned near the top of this post, this external file resource can be replaced and updated at will by export from a known final edit surface drawing resource in the project.
See the Civil 3D Surface Care post for more details.

All these Civil 3D surface details and workflows have to do with the specifications (Benchmarks) and feedback loops that we require in the data and the resultant surface(s).

We don’t need no stinkin badges…

We all already know what a surface is supposed to contain and how to build it. Right?

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