Strange difference in area

[OMEGA-ThundeR]

Hi,

I was just asked to calculate some area and for some reason i get different results.  i found out by splitting up the hatches and selecting again.

After some editing in the boundaries (top right, bottom left) and rehatched all the polylines i got the correct result (24xx m2)

However, i have no clue as to where the problem lays.  When i overlay the hatches, that seem to have the same coverage, they differ in a huge amount.

 

Any insights on where the problem may be at?  It can't be overlapping hatches, since those literally don't add up.

 

case.dwg

[lrm]

Deleting the hatch of your "original" geometry and giving the hatch command followed by a select window the following is output:

Command: HATCH
Select objects or [picK internal point/Undo/seTtings]:Specify opposite corner: 186 found
Select objects or [picK internal point/Undo/seTtings]:The Boolean operation on solid and/or surface bodies failed.
Modeling Operation Error:
Error Code Number is 18030
The Boolean operation on solid and/or surface bodies failed.
Modeling Operation Error:
Error Code Number is 18030

A hatch is created with an area of 2102.

 

Now delete this hatch and move the small polyline areas surrounding the some of the shapes (the only visible differences between the two object collections) as follows:

Now applying a hatch to the geometry yield an area of 2464 for the hatch!  Go figure.  It appears that the area of a hatch gets confused when hatch areas are adjacent.

 

A more foolproof way to compute areas for a collection of closed polylines is to:

1. Create regions from the polylines.

2. Union all the regions together.

The area of the one unioned region will be the total area.

 

 

Edited April 7, 2022 by lrm

[BIGAL]

To admin posted twice.