Convert percentages to angles???

[hunter3316]

Can anyone tell me how to convert crown and pav. percentages to angles... assuming no cullet.

I want to do it for these two diamonds:

1:
Depth:61.3%
Table; 56%
Crown: 14%
Pavilian: 43%

2:
Depth:59.9%
Table;58%
Crown:14%
Pavilian:43%

thanks for your great help!!!!

 

[pricescope]

Did you get the data from EGL report? If they are rounded there will be rather high error in HCA.

You can use these formulas to convert % to angles without culet:

CrownAngle = ATAN (2 * CrownDepth% / (100 - TableSize))
PavilionAngle = ATAN (PavilionDepth% / 50)

 

[MikeC]

----------------
On 4/24/2003 5:32

2 PM leonid wrote:
Did you get the data from EGL report? If they are rounded there will be rather high error in HCA.

You can use these formulas to convert % to angles without culet:

CrownAngle = ATAN (2 * CrownDepth% / (100 - TableSize))
PavilionAngle = ATAN (PavilionDepth% / 50)----------------

I was wondering how to do this as well.

leonid,
Thanks for the equation, but what does ATAN stand for?
Mike

 

[pricescope]

----------------
... but what does ATAN stand for?
Mike
----------------

Mike, ATAN (Arctangent) is reciprocal to TAN (Tangent)

On Windows' Calculator (Scientific Mode) select INV and hit TAN.

 

[hunter3316]

Thanks, thats exactly what I was lookin for.

To answer your question YES, these numbers are from EGL. How much of an eror could I expect, according HIC scoring. I supose theres no other way to fix this except to do the SERIN hu? Also whats the average error for converting EGL %'s to HIC scores?

Thanks!

 

[MikeC]

Thanks leonid. Originally I just had the pav. percentage and got a score of 1 on the HCA but was not to sure how reliable that was because it was a percentage and not an angle. After doing the conversion my score actually went down to .9. That made my day

 

[pricescope]

hunter3316:

----------------
I supose theres no other way to fix this except to do the SERIN hu?
----------------

Correct...

----------------
Also whats the average error for converting EGL %'s to HIC scores?
----------------

It depends on particular values. I just tried to plug pavilion depth of 43.0% and 43.5%. In both cases I've got HCA < 2 which is pretty good.

However, there will be more dramatic difference once you go closer to 43.8%-44.0% pavilion depth since diamond will leak more light under the table.

 

[pricescope]

Mike, actually when one enters pavilion or crown depth %, HCA converts it into angles anyway because HCA is based on angles.

We believe Sarin angle data are more accurate than depth% because later depends on accuracy of girdle and culet measurements.

Still, even angles data have certain error so don't fight for each tenth of HCA score