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When Tom Giffin tees it up, he sees golf courses differently than he used to. After more than three decades as a club professional, Giffin took on the role of manager of golf course rating and services for Mass Golf, one of the USGA’s 57 Allied Golf Associations (AGAs) around the country.
Now, instead of seeing a sloping fairway that causes a drive to bounce and roll into the rough, he sees a “W Adjustment.” His brain has been trained to think in a language that only course raters speak.
“You start to look at everything through the eye of the course rater,” said Giffin. “It’s just inescapable at a certain point.”
His experience isn’t unique. Anyone who gets involved in rating courses starts to see them, new and familiar alike, with a more technical eye. That’s because once you understand Course Rating, you can’t unsee the data embedded within every golf course.
While golfers are generally aware of the Course and Slope Ratings on scorecards and that they impact the calculation of a player’s Handicap Index® and Course Handicap™, their understanding of those numbers can get rather muddled rather quickly. A Course Rating™ is what a scratch golfer would be expected to shoot on a good day. The Slope Rating® reflects the relative difficulty of the course for non-scratch players. And therein you’ll find a common misconception: Giffin has found that many people believe Slope Ratings are comparable from course to course. They are not. “The only thing that is comparable is the Course Rating,” Giffin said.
Scott Hovde, the USGA’s director of Course Rating and Handicap Research, sees the same prevalence of that misunderstanding.
“A lot of people take one look and say, ‘Oh, the Slope Rating is 130 and the course I play is 125, so this course must be harder.’ But that’s not always the case, because the Course Rating could be two strokes lower on the course with a 130 Slope Rating, so it’s a lower starting point,” Hovde said. “It’s all relative. That’s probably the No. 1 misconception, that Slope is an absolute measurement of difficulty.”
The only way to determine the Slope Rating is to evaluate the course twice. Well, actually, four times when rating for both men and women: One evaluation for the scratch male golfer, one for the scratch female golfer, and then a evaluation for the male bogey golfer and the female bogey golfer.
Courses are initially rated when they are new and then again at least once every 10 years to account for any changes to the course or Course Rating System over time. If a course undergoes a major renovation, like rebuilding green complexes or re-routing holes, that course will need to be re-rated. Smaller changes, like adding or removing a few bunkers or moving a few teeing grounds, require a partial re-rating for any holes affected. Those can often be done remotely using aerial imagery, or a rater from the local Allied Golf Association can visit the site to evaluate the changes.
The AGAs are licensed by the USGA to determine the Course Rating and Slope Rating for each course in the United States. When your course needs to be rated, it’s the AGA for your region that will contact the course and come to rate it. The course raters at each AGA have received training from the USGA, and the system is standardized across the country.
When a course gets rated, typically a team of four to six raters visits the property to calculate the effective playing length and assess the course on 10 factors, specifically: topography, fairway, green target, recoverability and rough, bunkers, crossing obstacles, lateral obstacles, trees, green surface and psychological factors.
During the rating process, each obstacle factor is given a rating from 0 to 10. Zero means that the obstacle doesn’t exist. For example, if there are no bunkers on the hole, the bunker rating would be zero. A rating of 10 means that the obstacle is extremely significant, like a highly contoured green with a high Stimpmeter® reading.
Length is the first factor determined. To measure the length of each hole, the team uses surveying equipment or GPS receivers. Even that very first step can come with surprises: Often, courses have been using incorrect yardages on their scorecards.
“I don’t blame the golf course,” says Nate McCoy, director of Handicapping and Course Rating for the Iowa Golf Association, of such disparities. “The capability we have with technology now is so much better to accurately measure a hole than it was even 10 or 15 years ago.”
The raters take the actual length of the course and use it to determine its effective playing length. To get the effective length, raters evaluate factors such as elevation, roll – are landing areas on upslopes or downslopes? – and wind. Each variable that could affect the length is evaluated and assigned a value based on how severe it is, and those values are entered into the algorithm to calculate the effective playing length of each hole and the course.
Getting the effective playing length correct is crucial, because course length usually has the closest correlation to resulting scores as any of the rating system’s evaluation factors.
“The longer the holes, the higher the ratings tend to be just because it’s the one thing that a player can’t avoid,” said Hovde. “The length of a hole has a high correlation to scoring.”
The rating team uses the average carry and total distances for the scratch male and female golfers, and the bogey male and female golfers, based on the models in the Course Rating System. So, they go to those points in the fairway and measure the obstacles that exist around them within those 10 categories. The scratch male golfer, for example, has an average tee shot length of 250 yards at sea level (this is adjusted at higher altitudes). The raters go to the middle of the fairway, 250 yards from the tee and look for obstacles that exist laterally as well as in front of or behind the landing zone. Are there bunkers? Are there trees? Do any of the trees have overhanging branches that could come into play? Are there penalty areas or out of bounds? How thick is the rough? The raters evaluate all the obstacles in the vicinity of the landing area and use tables and adjustments in a field guide to determine the likelihood that they will come into play.
They also determine how much that obstacle could affect the player if they did encounter it. Raters measure everything from rough height to bunker depth. A deep bunker with a steep face will get a higher rating than a shallow bunker without a steep face.
Once the raters have recorded landing-area data for the tee shot, they start looking at the next shot, which could be another fairway landing zone or the green. Is there a forced carry? How large is the green being hit into? How long is the shot to the green? Are there greenside bunkers? If so, how deep are they? Is there trouble seeing a majority of the green surface?
“Let's say the scratch player was trying to hit their second shot from 210 yards onto a very big green, so that green target rating would be relatively low because the green is 32 yards in diameter,” Giffin says. “But if you’re going to try to hit the same shot 210 yards onto a green that’s 19 yards in diameter, obviously it’s going to be much more difficult to hit, so the green target rating will be much higher. It’s the length of the shot and the size of the green that mainly determine the green target rating.”
The data accumulation continues on the greens. How fast are they? How severe are the undulations?
These numbers are taken down for the scratch male and female players, and the bogey male and female players, from each set of tees being rated. All this data is entered into Course Rating software that contains all of the formulas and weightings used to determine Ratings.
“A giant math equation is set up to do the calculation based on all this data that we enter,” Giffin says.
The total number of data points put into the system at the end of a day of rating can be in the thousands when you have multiple sets of tees rated for men and women. The result includes the Course Rating, which you’ll recall is what the scratch golfer would shoot on a good day at that course. A Bogey Rating™ is also calculated, which is used in conjunction with the Course Rating to calculate the Slope Rating. If you’re mathematically curious, the algorithm subtracts the Course Rating from the Bogey Rating and then multiplies that number by 5.381 to arrive at the men’s Slope and 4.240 for the women’s Slope.
The key here is that the Slope isn’t calculated relative to par – it’s relative to the Course Rating. Factors like several forced carries will make a course harder for a bogey golfer than a scratch golfer, for example, because bogey golfers hit the ball a shorter distance. Bogey golfers are also typically less accurate than scratch golfers, so you’ll see a higher Slope Rating relative to the Course Rating at courses that have smaller greens.
A Course Rating of 70.4 means that, under normal playing conditions, a scratch player would be expected to average around 70.4 for their better rounds.
The Slope Rating can be anywhere from 55 to 155; the standard is 113, which is where a player would not gain or lose strokes relative to other players from the same tee. You can use the Slope to calculate your Course Handicap™ by taking the Slope and dividing it by 113. Take that number and multiply it by your Handicap Index and then factor in the difference between Course Rating and par, and you’ll have your Course Handicap to use against your playing partners in matches on that golf course. If you don’t want to do the math yourself, you’re able to easily calculate it in the GHIN app on your phone.
Once the Course Rating and Slope Rating have been calculated, they’re issued to the golf course. Sometimes, the results aren’t what the course was expecting. A current trend is tree removal, predominantly on older courses. When a course has done a lot of work removing trees, the assumption can be that the rating will change significantly. However, if the trees removed weren’t typically in play, you won’t see a significant change in rating. Tree removal is usually associated with making a course easier, but taking out trees that line out of bounds can actually make the course harder. since the out of bounds may come into play more often.
Giffin, McCoy and course raters around the country can’t help but see golf courses differently now that they are entrenched in the process of Course Rating. That can be a good thing, according to Hovde: Identifying obstacles and being able to quickly assess the severity of those obstacles is a useful skill for improving one’s scores.
“It helps you manage your game a little better because you’re trying to figure out where you don’t want to hit the ball, where you want your misses to be,” he said. “Working as a course rater makes you a more strategic player.”
For course raters, no obstacle goes unnoticed. For the rest of us, understanding how the system works will make those numbers on the scorecard a little less mysterious. And maybe getting a little insight into the Course Rating process will help you become more aware of the most treacherous obstacles on the next course you play.