| Jan 14, 2013
In the previous post we talked about how the related civil engineering disciplines “see” parcels and their data differently - so much for getting a nice brown-paper wrapper and a string on the parcel. Much like junk mail these differences of expectation will continue to show up. These show up in the AutoCAD Civil 3D interface and its functional tools.
Keep the tool-using thoughts I mentioned in the first Parcel post in mind. Do you employ the Parcel tool like an ax when it’s a chainsaw?
For many Civil 3D users our first misconception about Parcels is they are a new version of the traditional CAD documentation tool. In the old CAD days of civil engineering software, that’s what things that looked like parcels were. There’s no mystery as to the Why surrounding some of our Parcel confusion and frustration.
The Parcel Posts - a study guide to Read and Test in AutoCAD Civil 3D
Site Parcel Essentials – Part 1 | It’s Not Yo’ Daddy’s Parcel – Part 2 | To Edit Parcels is to Create? – Part 3 | Parcels Have Priorities - Part 4 | A Strange Universe of Parcel Inverses and Mapchecks – Part 5 | Dances with Parcels – Part 6 | Pack Dances with Parcels – Part 7 | Cycle Manipulations of Segments – Part 8 | Select Manipulations of Segments – Part 9 | Visual Manipulations and Many Segments – Part 10 | Site Parcel Alignment – Part 11
The Site Parcel is a Design Tool Dummy
The Site Parcel Feature in Civil 3D is a new beast entirely. It’s a set of model-based design tools built to help us find, correct, and manage what often may fall through the cracks in our old CAD primitive based and annotative centric workflows.
We had no choice. Our old school method was to deal with the parcel problem one parcel at a time – each was a separate thing. Nothing could be shared.
Civil 3D takes a collective model-based approach – the parcels and their parts are always related to a larger whole - a model.
If we just remain fixated on the annotated and published result, we may miss out on the benefits of the new Civil 3D approach.
Lamb or Land Chop
There are two really different (but at times related) processes going on inside the Site Parcel. One is all about grading and the other is all about what I like to call “land chop”. This pairing is like Shari Lewis and her puppet Lamb Chop of 1960’s fame who first joked about The Land of No Manners. Maybe a more current puppet reference to Jeff Dunham and Walter also makes sense. Who Really Talks to Who? is the question.
You can test the buried duality of Parcel Features easily enough at the most basic level.
Will a Feature line subdivide a Parcel? Nope.
In the Civil 3D Toolspace the subtle differences of what going on inside the Site Parcel and these two processes isn’t all that clear at first.
Everything in the Site Parcel appears to be thrown into only four piles in the Toolspace – Alignments, Feature Lines, Grading Groups, and Parcels.
What exactly we add to a Site Parcel collector isn’t directly exposed in the Toolspace. It is possible to have collected Parcel Segments within a Site Parcel , but they’ll appear nowhere in the Toolspace at all. Arrrgh.
When we delete one of the edge parcel segments of a Parcel there is no longer a Parcel. If we Select the visible Parcel Segments and the Feature Line - the AutoCAD Properties box tells the story. All the objects are still there neatly collected in our Site Parcel. But we have no Parcels at all?
Maybe you’d agree with me that there should be a separate Parcel Segments collection shown in the Toolspace. It would sure help us find and select Parcel Segments in different Site Parcels more easily.
If you agree, please submit a wish list request to Autodesk. You can do that from the Help Ribbon.
Parcels Ain’t Closed - They are Resolved
The Parcels collection in the Toolspace shows us ONLY what I like to refer to as “Resolved” Parcels.
You’ll often hear or read the phrase, “Parcels in Civil 3D must be closed.” I believe that the word “closed” employed in the typical Civil 3D chat about Parcels just creates misunderstanding and misconception.
The Survey term “closure” actually has nothing to do with what is actually going on inside the Site Parcel.
The Close property of a polyline or a Survey Figure has almost nothing to do with what’s really happening on the inside of the Site Parcel engine either.
Whew – that’s a relief to survey folks. Civil 3D isn’t totally crazy.
The Site Parcel Topology
Each separate named Site Parcel (displayed as a Site) collects “Parcel Segments” into a distinct “topology”. Technically this engine is a planar nodal topology.
You can visualize a Site Parcel as a transparent infinite sheet of plastic - Like a Layer that isn’t.
The only things collected on the topology's sheet are some specific linear objects.
Linear CAD primitives: lines, curves, and polylines are accepted.
The source geometry can even come from externally referenced dwgs and other CAD files (like DGN). That’s important to remember when you prepare to do your parcel work.
What about Survey Figures? Yup.
Currently, every Figure creates a Parcel Segment no matter what you do or want. In other words even if you uncheck the Lot Line box in the Figure Prefix Db Civil 3D adds the Figure as a Parcel Segment into the Site Parcel.
Currently, you can’t even delete the Figure based Parcel Segment record data in a Site Parcel even if there is nothing left in the actual records because you deleted (or removed) the Figures. This is Not Good.
Therefore, remember to publish your edited Figures in a clean drawing.
Civil 3D Alignment Features are allowed because they are linear in “nature” as well. However, an Alignment does not become Parcel Segments. Alignment Features within a Site Parcel interact with Parcel Segments and other Alignments.
Aren’t Feature lines linear geometry too?
They are. But it is safe to say Feature lines have another grading only job in the Civil 3D Site Parcel.
Personally, I’m of the opinion that we should have the choice whether or not a Feature line interacts with the Site Parcel. The choice for Figures should also actually work.
Projected into Space
The XY locations are “mined” from the acceptable linear geometries and projected into the Site Parcel topology to create both the resolved Parcel Segments and some hidden things we’ll call “nodes”.
The “nodes” are locations NOT “points”. God forbid we’d have another kind of point in Civil 3D.
Projected intersections between the allowed linear geometries also create nodes.
The node information in the topology tracks the connecting segments to any other nodes.
Only tangents and curve segments are allowed to connect nodes– no fancy multi-point curves are held in the topology.
Parcels are Resolved
Parcels are Resolved from the topology when the projected nodes are connected by segments. You can picture this as connect the dots with segments- the Parcel Segments then must enclose an area.
In the example below the east parcel segment is a single tangent created from an AutoCAD Line primitive. The endpoints of the east and west segments create nodes at the projected intersection nodes in the topology along the eastern segment.
We get a resolved Parcel.
Unfortunately, the generated nodes in the Site Parcel topology have no formal Civil 3D component (visual representation) in the Parcel Style. The only way (other than Grips) to see the invisible nodes is to employ a Label Style that places a Marker at Parcel Segment geometry locations. Our InstantOn and Jump Kit products contain a variety of Label Styles that do this for all the Features that can be involved.
If we view the AutoCAD Properties of a Parcel Segment in the AutoCAD Properties box, you’ll also note there is no exposed Geometry section for a Parcel Segment Feature.
That should give you a clue that the Parcel Segment we create isn’t exactly what we put in.
Next time we ask the question, “Is to Edit the same as Create?”