Map clean Workflow

[DaveM]

All,

I am trying to come up with a good order to run the map clean operations. This is a new command for me. Does anyone have any suggestions to the order to run them, or things to watch out for?

Thanks,

Dave

[AllenJessup]

This can differ with different types of data or just between drawing to drawing. I'd suggest reading the help and evaluating each operation in terms of what you want Mapclean to accomplish. Only use those operations that are appropriate to what you're doing.

What kind of data are you cleaning and what do you want as a result?

Allen Jessup

[DaveM]

On Thursday I am hosting a Lunch & Learn for my company to discuss parcels. I am hoping to introduce everyone to the map clean command. I have drawn a small piece of a sub division using a paper copy. I am going to show them how converting it to parcel segments before mapclean works, and after mapclean works. I learned about mapclean on the forums and really don't use parcels often, so I am trying to freshen up on the subject before Thursday.

[jmayo-EE]

For closed areas I seldom use mapclean anymore unless things are really messed up in the underlying geometry. What I do now is use PE to force close the pline if it is not and I just run boundary to get a nice new clean pline.

In any event, similar to Allen, when I need mapclean the options I use are determined by what I am cleaning. Options set will also be determined by the objects I want returned (line/curves, plines or 33 plines). Now if this were for legal parcels I would want to work with lines/curves and I might set, delete dups, zero len, extend undershoot, snap cluster or apparent int perhaps earase dangles...

[jmayo-EE]

also save different configs for different objects. One for parcels, one for contours, one for 3d polys, etc...

[DaveM]

Thanks for the Insight. I have been Playing with it for about an hour now. The only thing I am not sure of is, What is a snap cluster? I have already read the helps definition, but am having trouble imagining it.

[AllenJessup]

Snap Cluster Nodes will bring together the end points of multiple lines that end "near" each other. Near being defined by the tolerance set.

Personally, coming from a Surveying background, using Mapclean on parcels sounds a little scary. With messy data from a 3rd party it may be a start.

Allen

[Murph_Map]

As others said, it depends on what you have to work with and whaat you want as the end results. One tip I'll give to passs on in the Lunch & Learn is brfore using it do a save of the dwg, back it up if needed. Mapcleanup can destroy a dwg real quick.

[Neilw_05]

I'll present a scenario that might help get a feel for how to use the tool for parcels.

Suppose you have parcels drawn as polygons and you want to convert them to C3D parcels. Among the problems you'll need to adress are:

1) The polygons will have duplicate lines where they share sides. You'll need to get rid of those so there is only one line between parcels.

2) You'll want to be sure the polygons are closed, so you'll need to ensure there are no gaps (undershoots) in the linework.

3) You'll need to check for and resolve slivers, which occur when the linework for adjacent parcel edges are not exactly coincident.

4) You'll need to find and eliminate overshoots, which occur when lines cross each other rather than meet at a common point.

I'm out of time but perhaps someone else can present the order of options to clean up the linework for this scenario.

[Neilw_05 · Accepted solution]

Following up on my scenario, the workflow and order of operations is as follows:

1) Explode all the polygons (Map cleanup will miss problems if the linework is polylines)

2) Extend undershoots (This option will eliminate gaps and ensure that all lines intersect)

3) Break Crossing Objects (breaking the lines where they cross causes overlapping lines to have the same length which allows the Delete Duplicates option to detect them).

3) Erase Dangling Objects (gets rid of little pieces of overshoots left behind from step 3)

4) Erase short objects (This removes the ends of narrow slivers that may exist)

4) Snap clustered Nodes* (This step moves the ends of the slivers to be coincident with adjacent lines).

5) Delete duplicates (now that we've closed the gaps, broken all the lines where they cross, removed all the straggling pieces and lined up the slivers, we can find all the overlaps and remove them)

*This option will cause some lines to shift to new end points. Review the subheading "Objects to Anchor" in the "Select Objects" of the Cleanup help topic to control which lines may be moved and which cannot.

[Neilw_05]

I should add one more operation after #5: Simplify objects. This option will remove any unnecessary vertices along straight segements that result from the previous operations.

[DaveM]

Neil,

Thank you for the detailed answer. I have gathered from this thread that map clean can be useful, but you have to be careful where you apply it. Until I posted this thread I was under the impression that map clean was specifically designed to prepare line work for parcels, but now I see it has many more purposes.

I really appreciate everyone help in leading me to a better understanding of the map clean command!

[antoniovinci]

Dave, don't forget the true goal of _MAPCLEAN should be a correct topology (command _MAPTOPOCREATE).

Without it, your parcels will be "almost" right, but not completely...

[AllenJessup]

I hope that we're all talking about "Parcels" in the GIS form of the word and not the "Survey" form of the word. In my work any parcels drawn for use in a Survey are calculated not drawn. They may be calculated using Civil 3D but they are still the result of calculations.

I'll use the example of "Snap Cluster Nodes. That command will most likely change the bearing and distance on every line involved. So you may end up with closed parcels but not be matching outbound or right-of-way bearings. If the changes are large enough you may change lot area.

I hope I'm giving information that most people really don't need. I just get nervous when I see something like Mapclean being used on things like parcels (in the surveying sense)

Allen

[Neilw_05]

You are quite right to emphasize the danger of snap clustered nodes Allen. Users will need to be very judicious about using it on survey grade linework, if at all.

I agree with Antonio's comments about topology. Before generating C3D parcels from the linework it is best to first create a topology. In the process of creating a topology Map finds invalid linework and errors which you may not find with the Map cleanup tool.

[jmayo-EE]

Legal parcel lines are never edited. I was never under the impression from the OP that this was for a described parcel.

[AllenJessup]

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Neilw wrote:

I agree with Antonio's comments about topology. Before generating C3D parcels from the linework it is best to first create a topology. In the process of creating a topology Map finds invalid linework and errors which you may not find with the Map cleanup tool.

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Now that sounds useful. I'll have to give that a try next time I do parcels. The parcels I create are not subdivision parcels. Working for a Highway Department I do acquisition parcels along the length of a road. So I have a little different experience than those doing subdivision work.

Allen

[AllenJessup]

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@Anonymous wrote:

Legal parcel lines are never edited. I was never under the impression from the OP that this was for a described parcel.

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I just wasn't sure. Also, others read these thread long after the OP has the answer. So I'll admit to being over cautious.
 

Allen

[DaveM]

I am grateful that the dangers of map clean have been expressed here. I will certainly pass it on in the class shown. In the example I intend to show I retraced a subdivision plat. My only intention was to use map clean to extend the undershoots and trim the over shoots while holding the POB solid.

[jmayo-EE]

No worries here. 🙂