AutoCAD Map 3D General Discussion

AutoCAD Map 3D General Discussion

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New Member
atreu
Posts: 1
Registered: ‎11-12-2002
Message 1 of 3 (268 Views)

centerline

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11-12-2002 06:54 AM
I am a new Autodesk Map user. I have a project to do where I have been supplied cadastral data for a town (land parcels, sidewalks, parking lots) which basically outlines where the streets are. We want to draw in the center lines. How do I do that, and then how can I get an indication of the accuracy of the centerline placements. This will be done in Autodesk Map 5. Thanks to who ever answers.
*McIntyre, Mark
Message 2 of 3 (268 Views)

Re: centerline

11-12-2002 10:57 PM in reply to: atreu


I'm not sure what you mean by accuracy of the centerlines - Any information
you generate in the drawing will only be as good(accurate) as the data
supplied to you. One thing you'll want to be aware of is the fact that
street pavements are not always centered in the right of way. The simplest
way to draw your centerline of right of way would be to measure the distance
between the ROW lines and then split that distance and use the offset command.
If you want to center the street alignment you would split the distance
of the flowlines of the sidewalks and offset that half width. There are
a number of different ways to control your centerlines but without reading
the legal descriptions of the ROWs I can't say what the best way would
be. Just be careful. It would be nice if you were supplied with some control
such as section corners, property corners etc...

Hope this helps to get you on the right track.

atreu wrote:

I am a new Autodesk Map user. I have a project to
do where I have been supplied cadastral data for a town (land parcels,
sidewalks, parking lots) which basically outlines where the streets are.
We want to draw in the center lines. How do I do that, and then how can
I get an indication of the accuracy of the centerline placements. This
will be done in Autodesk Map 5. Thanks to who ever answers.

*Voigt, Bill
Message 3 of 3 (268 Views)

Re: centerline

12-13-2002 08:55 AM in reply to: atreu
Use the pl (polyline) command. To find the
exact centerline is to use the 'cal (calculate) command and enter (nea+nea)/2
when prompted for an expression. Autocad the prompts for each of the nearest
object snap points & the xpression calculates the mid point.  When
prompted for the next point use the up arrow key to recall the 'cal command,
then press the down arrow for the expression.

 

There is probably a way to repeat the sequence
('cal, (nea+nea)/2) so you only have to keep clicking on the left & right
sides of the street until you press enter.  I haven't figured that part out
yet.  You can also do an offset

 

I recommend that when drawing the centerlines, draw
the entire street, ignoring the intersections.  When one street is
completed, attach the attribute data (Prefix, Name, Type, Suffix).  Be sure
to digitize thestreets from low address to high.  I found it easiest
to use Object Data Table for the attributes. Once all streets are drawn
& attributed, you can then clean the data. Doing this in the recommended
sequence will preserve the data when objects are split, and minimize the cleanup
process.  If you split it manually, the OD is lost.

 

I also recommend building a network topology, which
will create intersection points and add the from/to nodes to the endpoints of
each street segment.

 

If this doesn't make sense, let me know. There's
lots of issues with centerlines that need to be considered.

 

 

-- Bill

 

William G Voigt    (415) 485-3366 voice
GIS
Analyst   (415) 485-3334 fax
Dept Public Works   1400
Fifth Ave.
City of San Rafael      San Rafael, CA
94901

 
 



style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">I
am a new Autodesk Map user. I have a project to do where I have been supplied
cadastral data for a town (land parcels, sidewalks, parking lots) which
basically outlines where the streets are. We want to draw in the center lines.
How do I do that, and then how can I get an indication of the accuracy of the
centerline placements. This will be done in Autodesk Map 5. Thanks to who ever
answers.
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