Zero Length line created - Not zero length

[AllenJessup]

This is just something that's bugging me but isn't really important. But it was important enough I had to figure it out.

I drew a line and the program said it was a zero length line but I can tell it wasn't:

LINE
Specify first point:
Specify next point or [Undo]: Zero length line created at (29079.661, 29450.046, 0.000)

Specify next point or [Undo]:

Command: LG

Select line: l
"0.00000000000364"

Yes. I can use lisp to measure a length that small. Why. I was trying to extend a line to an arc that should have been tangent but was missing the point on the arc. I now have an arc that hits the theo point within the distance above. More that good enough. But when I drew the line that I needed to tell me the distance I noticed it said it was zero length when I knew it wasn't. I'm thinking that the program either uses the current precision or 8 decimal places to make the determination.

Allen

[tcorey]

Hello Allen,

When you create a line, AutoCAD assigns coordinates to the endpoints of the line. With coordinates of 20000+/-, that's five digits left of the decimal, leaving eleven to the right of the decimal. You have fourteen digits to the right of the decimal in the line length. Move down to 0,0 and you can use a line of that length.

Test it by creating a line whose first endpoint is 0,0 and whose length is 0.00000000000364. AutoCAD draws the line. Now try drawing it with first endpoint at 10000,10000. AutoCAD tells you Zero length line created at....

Tim