autocad map drawing cleanup

[dlperrings]

To forum:

I us autocad map to create drainage area maps. After drawing the boundary lines i use drawing cleanup before creating the topology. I always seems that i flounder around in drawing cleanup for a while, much longer then i want to be there before i can create the topology.

Is there a good procedure for using cleanup to help shorten the process?

David Perrings

[Jmurphy]

If you are the one that is creating the boundaries and use proper techniques then you should not have to use the drawing cleanup that much. What problems are you running into? A few tips on using Cleanup, Watch the order that you select the action(s) in,(it does make a differences) Start with small tolerance and increase them as you go. Be aware drawing clean up is not a one button step it takes many little steps to clean up a drawing. Don't try to do everything in one step.

[dlperrings]

J Murphy,

I agree with you that input of the boundaries is vary important and if you do it right it should make drawing cleanup easier. The last time I had two cad techs put the boundary in and cleanup was a mess.

Also I think it is a good idea to say away from using curves in the boundary.

There are two functions which i do not understand and have never used

one is anchor and the other is simplify objects.

i do agree that it is a lot of little steps that is needed, i would just like to reduce the number of steps and have it be a little more predictable.

Thanks

David Perrings

[Jmurphy]

J Murphy,

I agree with you that input of the boundaries is vary important and if you do it right it should make drawing cleanup easier. The last time I had two cad techs put the boundary in and cleanup was a mess.

Also I think it is a good idea to say away from using curves in the boundary.

There are two functions which i do not understand and have never used

one is anchor and the other is simplify objects.

i do agree that it is a lot of little steps that is needed, i would just like to reduce the number of steps and have it be a little more predictable.

Thanks

David Perrings

The Anchor keeps the selected object as it is, an example; you have two lines that do not meet and you want to extend them to meet, if you select one as the "anchor" then that line will not change and the length and angle of the other line gets adjusted as needed to meet the end point of the anchor line. The anchor line will keep its original end points.
The simplify option works with polylines that have more than just the two nodes at the end points, what it does is remove any extra nodes (vertex) by the tolerances you set. A good example of using this is when you import contour lines from another file format that is made up of short line segments, the simplify option removes some of those short lines and makes the line smoother.
The help files for most of the cleanup options show a good visible example of most of the actions options.

[dlperrings]

Jmurphy,

Thanks for the reply. I have read everything in help so I am familiar with the help information and from the manual for Map. For my application i really do not need to use the anchor feature. As long as I am in control of entering the boundary lines I can control them so that the cleanup function is minimal. I often do not have that luxury. So I really am looking for a systematic way of executing the cleanup operation when there are a lot of errors.

What do you use Map cleanup for ?

David Perrings

[Jmurphy]

David,
To me drawing Cleanup is like drawing in 3D it's something that you may spend days on and not ever get the hang of it then there's times when you can be done in a few minutes. It just takes time and practice to get it to work the best way for you. There's been days when I used it on something I thought was simple to do and end up with a really trashed dwg then days that I thought it would be hours to clean up a dwg and next thing I know it's done in a matter of a few passes.
A systematic way depends on what you start with and what you want to end up with. There's no correct answer to it. My suggestions in your case (for what I know of your project) is first run the Remove Duplicates, then Break at Crossing, follow that by Erase Short Objects and /or Erase Dangling Objects, and then Extend Undershoots with Apparent Intersections. Last might be Simplify Objects.
I use Drawing cleanup when I was importing from other formats or using a dwg from a developer that had created the dwg in something else besides and AutoDesk project or didn't know how to use CAD.

[dlperrings]

JMurphy

well i found your blog and the two posts were helpful.

The first two cleanup operations that i think should be performed after making sure everything is on the layers that they are suppose to be and at the correct elevations is erasing zero length objects and removing duplicate lines.

The duplicate line problem has always been problematic for me since i cannot see the duplicate lines. Do you have any words of wisdom on this cleanup routine?


David Perrings

[Jmurphy]

The Delete duplicate has more power than most people think. Not only does it remove a exact duplicate of a line but you can have a tolerances also , so that means two parallel lines fall into that picture as well. The other thing is they do not need the same end points, think of the hands on a clock at 12:00 one of the hands is shorter but dwg cleanup can delete one of them. Then if at 12:01 if the tolerances is large enough it still will delete one hand, (As to what one is a good guess that's where the "Anchor" comes into play BTW)

[dlperrings]

JMurphy,

thanks for your reply. I am working on this and will post some more when i am finished.

david perrings

[trconnet]

This is a side suggestion concerning map cleanup.
Sometimes I use a program called MagicTracer to convert raster logos to DXFs. The DXFs are in version R14 that contains splines and other odds reminants.
Here is a solution for making cleanup easier.
After openning the dxf, export the drawing as a line ESRI shape file. In a new drawing import the shape; all the linework is converting to polylines. Map cleanup works a lot easier after importing. I am uncertain of how the conversion affects the coordinate values of the points on the lines, but for many applications it might be good enough.
Good Luck,
TC