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Message 1 of 8 (752 Views)

# AREA precision units

752 Views, 7 Replies
06-13-2012 02:33 AM

Hi every body,

i have a werid number appear when a get the AREA of the attached rectangles shapes especially when i use SMD ucs.

for instance see the rectangle C07  74X39=2886.00000000 BUT i get the area like 2886.000000003.

why the precisions dosesn't all 0 !!!!!!!

kindly see the attachment

thanks

*Expert Elite*
Posts: 28,262
Registered: ‎04-20-2006
Message 2 of 8 (749 Views)

# Re: AREA precision units

2886.00000000 BUT i get the area like 2886.000000003.

why the precisions dosesn't all 0 !!!!!!!

For all practical purposes those two numbers are equivalent.

Search for information on floating point math calculations.

What will be your measuring device?

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Posts: 33
Registered: ‎03-30-2012
Message 3 of 8 (737 Views)

# Re: AREA precision units

The accuracy is 0 before you rotate the rectangle, if you rotate in increments less than 90 it looses this accuracy giving an inaccuracy such as yours +/- of the value. But as noted the accuracy is pretty good for all practical purposes.

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Message 4 of 8 (717 Views)

# Re: AREA precision units

06-13-2012 03:43 PM in reply to: dlipscombe

dlipscombe wrote:

But as noted the accuracy is pretty good for all practical purposes.

Pretty good?  It is dead on for all practical purposes.
I think units (mm, M, light years...) need to be specified along with magnitude to have any real meaning.

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Message 5 of 8 (710 Views)

# Re: AREA precision units

Autocad is a precision software, you dont expect to get two different values just because you rotated an object 30°, no matter how minute the discrepency it should give the same reading in all circumstances, after all rotating an object doesnt change the object? Yes your right it is dead on for all uses, nobody ever needs that sort of accuracy.

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Posts: 28,262
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Message 6 of 8 (700 Views)

# Re: AREA precision units

06-14-2012 06:00 AM in reply to: dlipscombe

dlipscombe wrote:

Autocad is a precision software, you dont expect to get two different values just because you rotated an object 30°,

What is the precision of AutoCAD software. Be specific.
What is the programing routine for calculating the new position. Be specific. (you may simplify this one with hand-calc trig rather than specific programing algorithm)

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Registered: ‎03-30-2012
Message 7 of 8 (697 Views)

# Re: AREA precision units

As we can see from the OP they offer 8 decimal places but can only deliver 7, should not offer something you cannot achieve.

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Message 8 of 8 (693 Views)

# Re: AREA precision units

06-14-2012 07:00 AM in reply to: dlipscombe

Precision is not about decimal places but significant figures.  There are 13 significant figures, not 8 decimal places.  The original drawing did not have perfectly drawn rectangles.  The dimensions were off in the 12th significant figure (which is superb unless you want perfection).

There is no need to dimension or worry about these kinds of extreme precisions that cannot be measured or produced by machine.  A typical surveyor might measure with an error of 1 part in 5000. So a 74m property might actually be 74.01m or it might be 73.99m.  The area listed is well within the measurable precision.

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