Precision difficulty

[Dadgad]

@steven-g     Live and learn, thanks for the correction and elucidation.

You reminded me of a great interview with a savant who remembered the value of PI to about 22,500 places.

It took him about 5 hours to recite it from memory, which means that without making any mistakes he

added another digit about very .8 seconds.  I'm guessing he doesn't write a shopping list when he goes shopping.   

 

[steven-g]

 Ohhh certainly not intended as a correction, just an observation.

My memory is certainly not that good, but I have given up writing shopping lists (because every time I write one I forget to take the damn thing with me to the shops, and that isn't a joke)

[Dadgad]

In one of my recent posts to silverfox I said that I thought decimal precisionof 8 was it for the software.

I remember once hearing a memory expert/trainer say that in order to remember everything on your shopping list, first take a mental picture of all of the items on the hood of your car.

I don't write one either, but if I bothered to, I WOULD remember to bring it.

Damn, all these groceries are heavy!  Where did I park? 

 

Edited June 8, 2020 by Dadgad

[lrm]

A note about AutoCAD's precision.  The maximum precision for AutoCAD is about 15 significant digits (not to be confused with decimal places). The maximum number of decimal place digits depends on the extents of the drawing.  If you are drawing a wrist watch you will have more decimal places of precision then if you are drawing a 747 Jumbo Jet.  The 8 decimal places that are set by the units command is the maximum number of decimal places you can see with a command like dist.  Geometry may actually have more than 8 decimal places.  As proof, try the following:

 

Create a line from 0,0 to 1.2345678987654 

Note that the x coordinate is rounded to 1.23456790  the number displayed has been rounded to 8 decimal places.

Now scale this line by 1000 about point 0,1. Note that the end x coordinate is:

1234.56789877

More than 8 decimal places was in fact stored for the original  line but its displayed value was rounded to 8 decimal places.  Scaling the line by a thousand reveals more of the precision.

When the line was scaled by 1000  three additional digits of precision became visible.  The digits were part of the first line but the properties command rounded the number to 8 decimal places.  The same result wold be found with the dist command if the  units command set the displayed decimal places to 8.

 

As noted by others, silverfox's precision issue can be address via dimstyle. AutoCAD is pretty precise although it doesn't always show it!

 

 

 

[BIGAL]

There is a dwg called solar very old and its the Solar system rings with a dot, click on the dot and its a planet, ok you can go to the moon, then to moon lander, right down to the base plate of the lander leg. Ps zoom in on bolt "made in china"

 

The point being the order of precision with big numbers.

 

SOLAR.DWG

[lrm]

The drawing assumes the size of the solar system is defined by the distance from the sun to Pluto which is about 4.5 billion km. Double to get the diameter of the solar system  and then  divide by 10^15 you get about 0.00001 km = 0.01 m  = 10 mm. 

10 mm is about as small as you can measure in  an AutoCAD drawing of the solar system.  

 

In my early days in CAD the system I used was limited to 7 significant figures (similar to today's 3ds Max).  We could model the continental US (about 3000 miles) to a precision of about 1 foot.  With today's AutoCAD the precision would be about 0.00000001 feet!