I received a drawing to look at this week for an unrelated reason, and I noted something that strikes fear into my heart.

In the Prospector Tab, there was a Site called “MIGRATED PARCELS”

It might as well have said “ANTHRAX SPORES”

Because that is how diseased migrated parcels are.

Perhaps, that sounds harsh. But let’s flash back to June 2005. Yes, June 2005. For those of you old enough to remember June of 2005, that was Civil 3D 2006 PRE SP1. And we all know that Civil 3D 2006 was a tough dinner date before Hot Fix 2.

I was working with a group who was new to Civil 3D. The idea of free form creation of parcels was a foreign one to them, and to be frank, to me as well. I was pretty new at this. Since they had a land desktop project that they had started with, and since there was a migration option for parcels under “Import Data from Land Desktop” it seemed a perfectly reasonable solution- let’s bring ’em forward.

So we did.

All seemed fine. They were parcels like any other, you could apply styles… But then, the inevitable editing has to happen.

See, I get tricked into believing the Stone Sculpture people. They tell me- this site plan isn’t going to change. It’s locked in stone. No way no how. The county has approved it this way. The told is it will never change. Let’s just bring it in the easy way.

Then three days later- kaboom. Changes. So we try to grip edit these beasts and get the job done. It seems to go OK.

BUT-

I spent the next few weekends at their office in my sweatpants and ball cap trying to figure out why we couldn’t open these drawings anymore. It just seemed so unreal to me that a few weeks before, I had been at BootCamp with a gleam in my eye totally psyched to hit the streets with this. I had drawings in to Autodesk that came back with the “We’re sorry, it’s a known issue” response. What the heck? WHAT is a known issue?

Why didn’t this work?

I couldn’t tell you then. It took me until June 3, 2006 to truly figure it out and articulate it. (See Parcel Rules, Explained)

I also noticed the same thing happened when you brought Parcels in through LandXML, or defined side-by-side parcels from closed polylines.

Here is why: DUPLICATE EDGES

In Parcel Rules, we see that TWO LOTS share ONE LOT LINE.

When you migrate parcels from Land Desktop, it sees each one individually and NOT as part of an overall web of topology. LandXML does this to a lesser degree, but it still does it. Here are some examples:

Now let’s look at a LandXML example.

Here is the drawing as done in a Civil 3D Topology. I’ll export to LandXML and bring them back in.

It is a tight topology. No errors. Carefully constructed so that each parcel segment connects but does not overlap with another side geometry element.

LandXML Export- JUST the parcels.

New drawing (slightly different style template)
LandXML Import

The moral of the story:

Migrating Parcels from Land Desktop = NEVER

Migrating Parcels through LandXML = KNOW THE LIMITS

How do we do it then?

It is not as “instant” but the rewards are many if you use your old parcel linework as a guide and recreate those parcels using the layout tools. You can use free form create and just snap, crackle, pop through your whole site quickly.

Of course, this depends on good drawing geometry. But that, my friends, is the subject of another post.

Related posts:
Parcel Rules Explained
How to Corrupt a Civil 3D Drawing in one easy step
How to Approach Site Geometry
Site Geometry and Transitions