Ball distance and symetry info

Summary of Method

-Using equipment at the USGA Research
and Test Center, currently referred to as the
Indoor Test Range (ITR), the aerodynamic
properties of a sample lot of golf balls are
completely characterized by the coefficient
of lift (CL), and coefficient of drag (CD).
-Using the aerodynamic coefficients, the
overall distance (carry plus roll) of a
sample lot, as well as its spherical
symmetry, is determined for a specific
combination of launch conditions (ball
speed, spin rate and launch angle) as
determined by a mechanical golfer.

Significance

-This method is used to determine the
overall distance and symmetry of golf balls
for a given set of launch conditions. The
data obtained from this method is used to
ascertain the conformance of the golf balls
to the Overall Distance and Symmetry
Standards as stated in the Rules of Golf

-The overall distance of the ball shall not be
greater than 317.0 yards. A maximum test
tolerance of 3.0 yards is associated with this
test.

In addition, the ball must not be designed,
manufactured or intentionally modified to
have properties that differ from those of a
spherically symmetric ball. A spherically
symmetric ball shall not exhibit statistically
significant differences in carry distance
greater than 4.0 yards or in flight time of
more than 0.40 seconds regardless of which
axis the ball is spinning about when
launched.

-Only those balls that have already passed
the conformance tests for Weight, Size, and
Initial Velocity will be tested for
conformance to the Overall Distance and
Symmetry Standards.

Launch Conditions

Launch Condition Mean Acceptable Range
Angle 10° +0.5°
Spin 42 rps +2.0 rps
Swing Speed 120 mph +0.5 mph
Ball Speed 256 fps Reference*

The reference ball speed of 256 fps represents the speed
after initial aging to a near steady-state condition