AutoCAD 2010/2011/2012

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Member
whispering
Posts: 4
Registered: ‎08-07-2009
Message 1 of 36 (2,061 Views)

Autocad gives the wrong area for a polyline

2061 Views, 35 Replies
04-05-2011 03:08 AM

Autocad 2011 and 2011 LT both give the wrong area for sertain polylines. While Autocad 2005 gives the correct area.

 

Its terrifying how many official documents may be wrong because of this bug.

Active Contributor
wundrlik
Posts: 39
Registered: ‎09-23-2008
Message 2 of 36 (2,028 Views)

Re: Autocad gives the wrong area for a polyline

04-05-2011 04:53 AM in reply to: whispering

I do understand that the area is different in 2011 (2010 matches the value from 2005 BTW).  Try this and see that both are incorrect as well...

 

Draw a closed polyline around the perimeter.

Draw closed boxes for each internal island (pillars or columns I'm going to assume)

Hatch the area inside the outter perimeter using pick internal point.

 

You will see that the area of the hatch is 294.16 (actually 294155229)

 

So in theory, neither version of AutoCAD is showing the true area you are polylining.

Ryan A Wunderlich
Royal Caribbean Cruises Ltd.
*Pro
nestly
Posts: 1,283
Registered: ‎09-03-2010
Message 3 of 36 (2,012 Views)

Re: Autocad gives the wrong area for a polyline

04-05-2011 05:52 AM in reply to: whispering

You'll be even more terrified to know that 2011 will give you different areas as you move the polyline around relative to the origin. :smileysad:

Distinguished Contributor
pkolarik
Posts: 128
Registered: ‎06-07-2010
Message 4 of 36 (2,003 Views)

Re: Autocad gives the wrong area for a polyline

04-05-2011 06:17 AM in reply to: nestly

I just tried making a square 30'x30'.... then proceeded to move it farther and farther from the origin (way, way, way past where it's just a dot on the screen)... the square footage never changed. Not once. This is 3 places to the right of the decimal and no change...  <<shrug>>

*Expert Elite*
GrantsPirate
Posts: 1,550
Registered: ‎08-15-2008
Message 5 of 36 (1,989 Views)

Re: Autocad gives the wrong area for a polyline

04-05-2011 07:18 AM in reply to: wundrlik

Hatch is always unreliable, regions will give you much better results.

*Pro
nestly
Posts: 1,283
Registered: ‎09-03-2010
Message 6 of 36 (1,974 Views)

Re: Autocad gives the wrong area for a polyline

04-05-2011 08:46 AM in reply to: pkolarik

 


pkolarik wrote:

I just tried making a square 30'x30'.... then proceeded to move it farther and farther from the origin (way, way, way past where it's just a dot on the screen)... the square footage never changed. Not once. This is 3 places to the right of the decimal and no change...  <<shrug>>


 

It doesn't happen all the time, and I can't offer an explaination, however the point is that you'll never know know if you're getting an accurate area unless you always double check your polyline areas.

 

Here's a visual demonstration using the OP's drawing.  http://www.screencast.com/t/p4ILQqj2ujLv

 

 

Distinguished Contributor
mmcmanus
Posts: 110
Registered: ‎08-07-2006
Message 7 of 36 (1,965 Views)

Re: Autocad gives the wrong area for a polyline

04-05-2011 10:09 AM in reply to: whispering

I checked the drawing and came up with the same area every time. The area for the hatch matches the total area of your shape minus the 10 internal areas that were not hatched. Even if I move everything 1,000,000 units in any direction, the areas are still the same.

 

*Expert Elite*
GrantsPirate
Posts: 1,550
Registered: ‎08-15-2008
Message 8 of 36 (1,963 Views)

Re: Autocad gives the wrong area for a polyline

04-05-2011 10:15 AM in reply to: mmcmanus

I came up with at least three different values depending on where the hatch was moved, and that was using 2012.

Distinguished Contributor
mmcmanus
Posts: 110
Registered: ‎08-07-2006
Message 9 of 36 (1,961 Views)

Re: Autocad gives the wrong area for a polyline

04-05-2011 10:17 AM in reply to: GrantsPirate

Interesting. I checked on 3 different machines with 3 different verticals (AutoCAD 2011, Map 3d 2011, and Civil 3D 2011) and got the same numbers each time. I wonder why it is different on your setup?

*Expert Elite*
GrantsPirate
Posts: 1,550
Registered: ‎08-15-2008
Message 10 of 36 (1,959 Views)

Re: Autocad gives the wrong area for a polyline

04-05-2011 10:20 AM in reply to: mmcmanus

I don't know. 

Plain AutoCAD 2012

Dell precision T7500

Dual Xeons

Win7 64 pro

I had units set to architectural/ precision 1/32

 

One of those perhaps?

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