ode - The re-evaluation of courses for slope and ratings has been going on since the USGA introduced the concept of the World Handicap System 3 years ago. This is their brief mention of it in a summary of all changes the WHS would bring: "course ratings will be expanded and will serve as the foundation for handicap index calculations under the WHS".
Previously, a member club/course had to pay to have course raters come in and perform an evaluation, actually play the course before or after their site visit (recommended), and then submit their initial calculations to the courses' governing body for approval, i.e. the Kansas Golf Association, before informing the clubs management of the ratings.
I'm speculating that the course rating 'expansion' was based on changes to the formulas from golf associations around the world on what was formerly used internationally, melding them into one calculation. Thus, a revised course rating was based on prior calculations but 'tweaked' based on new criteria.
In addition to length from each tee, a key to the rating for each course is the 'obstacle value'. Those are:
The obstacle stroke value is a numerical evaluation of all obstacles (topography, fairway, green target, recovery and rough, bunkers, out of bounds, water, trees, green surface, and psychology) on the golf course. It is also highly probable that the Obstacle stroke value of the two golfers will be different. Generally, the nearer the obstacles are to the landing zones the higher the rating values.
Topography-A factor of how mounds and slopes affect the stance or lie in the fairway landing zone and whether the shot to the green is uphill or downhill.
Fairway-A measurement of the probability of hitting the fairway.
Green Target-A measurement of the probability of hitting the green from the fairway landing zones. The relationship between the length of shot played and size of the green determines these values. (i.e., long shots to small greens will generate higher values than short shots to large greens)
Recovery and Rough-A measurement of the probability of missing the tee shot landing zone or green, and the difficulty of recovering if either is missed.
Bunkers-A measurement of the effect bunkers have on play based upon their proximity to target areas and the difficulty of recovery.
Crossings-A measurement of how much the out of bounds will come into play based upon the proximity of the boundary to the fairway landing zone or green
Lateral-A measurement of how much the water will come into play based upon its proximity to the fairway landing zone or green.
Trees-A measurement of how trees effect the play of the two players based upon the size and density of the trees, their distance from the center of the fairway or green, the difficulty of recovering from the trees, and the length of the hole.
Green Surface-A measurement of the difficulty of a green from a putting standpoint. Speed of the green and surface contouring are the main factors.
Psychology-a measurement of the cumulative effect of the other nine obstacles.
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