Measurement Precision Errors
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I've been trying to use SU to do some geometry that should result in the Golden Ratio or, 1:1.61803. The geometry is to erect a perpendicular line of the same length at the end of a base line forming a 90 degree angle. Then a circle with radius half the length of the lines is drawn with the angle point as origination. An hypotenuse is then drawn from the center of the vertical line to the open end of the base line. Next the length of half the original lines is marked on the hypotenuse using the intersection with the vertical leg of the angle as origination. Then a circle is drawn using the open leg of the baseline (opposite the angle) as the origination and a radius to intersect the point on the hypotenuse. Where that circle intersects the baseline should mark the 0:0.61803 ratio on the baseline.
When I make a drawing starting with a square with 10" sides and drawing arcs of correct radii at the appropriate points of origin then measure the distance along the baseline I get a ratio of 0:61730. The model info settings are for decimal with 6 point length precision, length snapping set to one unit at that precision, and angle settings at 0.000 and 1 degree.
Why does SU not produce the correct geometry?
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SU can't really do such things that small, try making the geometry bigger then scale it down. For ex. do all of what you said except x100 000, then when your done scale it down x100 000.
But may I ask, why not make it 1:1.6? So much more simpler and less headaches.
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So, SU lacks precision?
I can make any ratio I want, obviously. The question is why doesn't SU have the requisite precision?
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Hi folks.
Beware of circles drawn by SU. On;y the endpoints of the segments making up the curve are accurately localized on the circumference. Any other point along the segments making the curve are not precise and any intersection will not yield what you want.
To increase the precision, you can increase the number of segments for the circle.
By the way, the Rectangle Tool can produce a dashed diagonal that signal a square and also another that signal the golden ratio. Use the Help Menu of SU and type Golden ratio in the search field. You shall get a few hits (I got 10 results), the first one being:
Try to avoid drawing really tiny rectangles where one side is less than about 1/16 inch or 1 millimeter. SU is not able to automatically close a face that has such small sides. If you need such small surfaces, draw them larger than life size and scale down when done.
Just ideas.
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Somewhat off-topic, but this from Wikipedia:
In the fields of engineering, industry and statistics, the accuracy of a measurement system is the degree of closeness of measurements of a quantity to its actual (true) value. The precision of a measurement system, also called reproducibility or repeatability, is the degree to which repeated measurements under unchanged conditions show the same results.[1] Although the two words can be synonymous in colloquial use, they are deliberately contrasted in the context of the scientific method. -
If you want to draw accurate arcs/circles, tangents, intersections etc etc then you might try my 'True Tangents' - the tools in the script do various tasks, including giving you the true intersection cpoint[s] between a selected arc/circle and a line which you can then use for a replacement arc/circle and edge that will have proper intersections with the line...
See here http://forums.sketchucation.com/viewtopic.php?p=160780#p160780
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