Parcel Removal

[Anonymous]

Hi,

I have created parcels (Create from Objects) where the parcels are in a "U"
shape. There is a common arc that caps the parcels and the road to a cul-de-sac.
The road is being defined as a parcel and I would like to exclude / remove /
delete it.

If I choose to remove a parcel element, it undefined the parcel. It also
undefined the object not only for the road, but also 1 of 2 adjacent parcels
that is using the object.

Work around: Break the arc and only select the objects that make up the parcels.

Isn't C3D creating unique parcel objects from the base geometry?

Why can't I remove the parcel element for the selected parcel and keep the
portion that is used for the other parcels intact?

Mark Martinez
The D.C. CADD Company

[Anonymous]

Hi Mark,

I'm not sure I understand your description of how the parcels are
constructed, but I'll take a shot at answering your questions:

With the "Create parcels from objects" command, each AutoCAD primitive
(polyline, arc, line) is converted into a matching "AECC_PARCEL_SEGMENT"
(lot line). If the original object was a polyline, then it will be
converted into a single multi-segment lot line. In addition to these lot
line objects, there are "AECC_PARCEL" objects that represent the enclosed
regions. The lot lines define the parcels, so that whenever the lot lines
are edited, the parcels automatically update to reflect the changes.

Since each lot line is conceptually just a "smart polyline", it can
really only represent one connected string of arcs and lines. Suppose that
you've got three different lot lines connected as follows:

A -------------------------------------
| |
| |
B C

And now you delete the piece of A that falls between B and C


A --------- D ---------
| |
| |
B C


The line A can't be represented as a single polyline anymore, so the
question is what do you do with the new "D" piece? One possibility would be
to create a new lot line that would keep the parcels that depend on the "D"
piece connected, and your example would work

Another way is to turn the "D" piece into "construction geometry" that
stays associated with lot line "A". This construction geometry can be used
as a basis for further edits to lot line "A". For instance, you could
reconnect the "D" segment using an arc instead of a line (OSNAPS make this
easier). Construction geometry is not used to define parcels, so that's why
the second parcel disappears. This is the way the "Delete sub-entity"
button on the layout toolbar currently works.

We will need both methods for a complete parcel editing solution, but we
chose to implement the "construction geometry" method first because it
provides a good foundation for work that we have planned in the future.

You'll notice that this behavior is similar to what happens with the new
alignment object. When you delete a curve from the middle you'll notice that
all of the station labels disappear from the last half of the alignment.
That's an indication that those segments have been turned into construction
geometry and are no longer part of the "official" or "solved" portion of the
alignment. You can then reconnect the construction geometry by selecting a
new constraint to replace the deleted curve segment.

If you want to make lot line construction geometry more obvious, set up
the construction geometry layers so that construction lines display
differently. After creating a new site (done automatically when you "Create
Parcels from Objects"), go to the toolspace tree view and bring up the site
properties dialog. On the "3D Geometry" tab, set "Construction Line Layer"
and "Construction Arc Layer" to a new layer with a dashed line style and
different color. When you exit the dialog, REGEN the drawing, and the
construction lines should be easy to spot.

Hope this helps,

Chris Putnam
Software Engineer
Autodesk Civil 3D Team