Automatically delete overlapping plines.

[jmorrison2Q85R]

Hello everyone,

I am working with some GIS data which has been manipulated to analyze digital elevation data and create a polyline for area with slopes at different values.  The methodology of this creates a problem though.  In areas where slope increases, a line is created where the slope starts and where it ends.  Since the slopes are sequential, this means that there is a line where 10% slope ends and that is exactly the same place where 15% begins.

I need a way to quickly delete the line on the lesser slope layer.  I have arranged the draw order such that the lower slopes are drawn on top of the higher slopes.  I've tried lots of different options with the overkill command but I'm not having much success.  Often, the overkill command does nothing, other times it will combine the two lines at what seems to be a random point in the middle.

Can someone help me out here?  Sample file attached.

[ChicagoLooper]

Unfortunately your drawing is not good. Some, not all, of your 10% lines end where 15% begins. This is what you're calling overlap or where you consider a transition from 10% and 15% slope takes place. Please explain what is happening where 10% lines do not overlap with 15% lines. Is there no transition? Some, not all, of your 25% lines end where 30% begins. Again, this is what you're calling overlap. Please explain what is happening where there's no overlap between 25% and 30% lines.

Overkill is not the answer. Believe it or not, your lines represent slope of ground surface, not the end of one slope and the beginning of another.

It appears you are trying to analyze slope using GIS data--data which has already been processed in GIS. You have exported the processed GIS data to AutoCAD which then uses lines to represent your slope. You should bring in the GIS data without any fancy-schmancy processing. If you want to process the slope, then best bet is letting Civil 3D or Map 3D do it, not GIS. What is your GIS  data? shapefile? gdb? ASCII files? Please be specific.  

Please disclose what are you trying to accomplish? Can your workflow be performed entirely in Civil 3D or Map 3D? Or should it be performed entirely in GIS? Can your goal be accomplished using topographic contours? Or a TIN? Using both GIS and AutoCAD, instead of just one, might be inefficient.

[jmorrison2Q85R]

You may be entirely correct.  I am relatively new to AutoCAD and the GIS information originates with a 3rd party.  My understanding is that the 3rd party uses ArcGIS to analyze a raster digital elevation map.  From the raster data, the slopes are calculated and then the boundaries are drawn as shape files before the map is exported as a dwg.  I understand that Map3D has some capabilities here but my inexperience with GIS limits my understanding of what we could be doing better.

With regard to simply using overkill to address the overlapping lines:  The different levels of slope do not always overlap, and to honest, I haven't spent that much time trying to figure out exactly why.  My main concern is simply cleaning the drawing as it is presented.  What really doesn't make sense is why overkill doesn't delete the extra lines.  As far as I zoom in, the lines overlap exactly.  So much so that when viewed with linetype generation off, everything looks good.  However, we plot in monochrome so I created linetypes to take the place of colors, which is where we discovered the overlapping lines.

[ChicagoLooper]

Understood. Overkill is not, and shouldn't be, part of your workflow. Even if overkill successfully eliminated the duplicate lines you still wouldn't be able to analyze slope in a meaningful way. Yes, You can look at slope data, but not using your approach.

I am guessing the lines you really want and need are topographic contours which can be generated from different sources (some sources are more appropriate than others, it all depends on your site) such as digital raster data. Slope is typically not represented by polylines. 

AutoCAD can utilize your raster data and generate a TIN surface. The TIN can then be used perform slope analysis. For example, display a TIN surface using topographic contours then add slope arrows. The contours indicating elevation and the arrows displaying slope at various locations throughout the surface.

How AutoCAD can contribute to your slope analysis:

Arrow length=magnitude or steepness

Arrowhead with Text=direction of down slope and Text=grade%

You can create a meaningful drawing with digital raster data using Civil 3D exclusively. Given your explanation and data source, GIS is not needed.

[jmorrison2Q85R]

I will have to do some research on the TIN surface but I have no doubt that there are other ways to do what we are doing.  However, this is how my company has been doing this and at the moment I am looking for a way to accomplish the task at hand.

Please note that these slope lines are not topographical contours.  See the attached image, the white lines are contours.  The slope lines simply represent "keep out" areas where the slope of the terrain is too great for the structures we are building.  More accurate analysis is surely possible but this serves our purpose at this stage in the project's development.

Perhaps this is unorthodox, and I appreciate the tip on better ways to analyze the slope, but any thoughts on why overkill doesn't work to delete lines on top of other lines?

[ChicagoLooper]

'Why is overkill not working?' From an objective view (and by objective I mean a neutral view and not from a biased we-have-been-doing-it-this-way-for-years-so-it-must-be-right-view) the reason overkill isn't working is due to the duplicate it must delete. Somewhere, somehow and some way, AutoCAD must determine, without any input from you, which of the 2 overlapping polylines it must delete.

Case in point:. the 15% slope line is deleted if it overlaps with a 20% slope line, but if a 15% line overlaps with a 10% line, then the 15% line is not deleted, it's retained. The decision to delete or retain is not built into the command. It's a user decision, not an overkill decision. And the only reason anyone or anything can ascertain whether your line is a 10% and 15% line is due to an arbitrarily named layer. Your layers could have been named Bart and Homer instead of 10% and 15%. Should overkill decide whether to delete Homer or Bart? Should overkill decide to delete 10% or 15%? How would it know the difference between Homer and Bart? Or between 10% and 15%.

A more appropriate way would be to use MAPCLEAN command.

Go to Tools Tab=>Map Edit Panel=>Drawing Clean Up Icon. Using MAPCLEAN allows you establish parameters to clean up your drawing, which in your case is to delete duplicates. Parameters include: 1) select objects, 2) cleanup actions and 3) cleanup methods. Your input, or your decisions when establishing these parameters include, but are not limited to: how to select overlapping objects that you want cleaned up, whether original objects should be deleted or retained once cleanup has taken place, whether new objects should be created to replace any deleted originals, and what layer to should host any newly created objects. 

The clean up parameters give you control, not AutoCAD.

[parkr4st]

OP  simply you need areas of given slope?

MAPEXPORT the data to a SDF file as polygons from closed polylines in your posted file - not not all the plines a closed and I didn't close them.  your job  🙂  clean up the linework as you need it.

put that SDF file in a map and Feature Overlay Identity the SDF to itself.

That will build a set of polygons by layer which when themed show the areas of slope of given slope range

files attached.    D&D the .layer into a blank map to see the theme.

If you were given a FDO file of any format this process should work directly on that file.