Changing a course due to slope rating?

[Erik J. Barzeski]

I mean, slope rating is essentially how easy it is for the bogey golfer to be.... a bogey golfer. Shouldn't the ideal be a high course rating with a low slope rating?

Kinda.

It's a measure of the relative difficulty. But if the base difficulty (the course rating) is high, it's really, really tough to get a low slope rating. Like I said, you could maybe design a 74.6/110 course, but I'd love to see it, because that would be WACKY as heck. If it's even possible. Bogey ratings include the hazards and such all along the corridor, plus length is still the over-riding factor. So it may not even be possible.

If your CR or slope was arbitrarily made higher ( by perhaps arguing width didn't make it easier ) your members would travel poorly with their handicaps.

Correct.

In theory, Tom Doak's Memorial Park in Houston, where he eliminated a lot of sand in favor of other grass hazards that challenge pros a bit better, should be as good an example of a relatively higher course rating with a relatively lower SLOPE rating.  Has it been rated yet?

https://ncrdb.usga.org/courseTeeInfo.aspx?CourseID=4532

74.2/128
71.1/121
70.6/117

A sampling of the ratings/slopes from different tees. Nothing really out of the ordinary. 74.2/128 is a ratio of 1.32.

There has to be more to it than that.  The change in the Course Rating/Slope by adjusting fairway width in the landing zones from 25 yard to 50 yards would be minimal.  I re-calculated the CR/Slope for a number of courses with average fairway widths of 25 yards, changing the widths to 50.  The CR dropped by .3 and the Slope by 3 points.

Yep. Wider fairways make the course easier by the way ratings/slope are calculated. There are ways to say "oh, this fairway runs all the way into the water, so the effective width is narrower, plus we have Bounce and roll-off, which effectively makes the water (penalty area) larger. Good raters understand this, too, and adjust accordingly.

[Michael Felton]

Is there a master database.  I would be interesting to see which courses have the biggest spreads in their rankings between course rating and slope.

Well I did a little digging. 772 rows of men's tees (I deleted any ratings below 65.0), and calculated the bogey rating for each course.

Then I took the bogey rating and divided it by the course rating.

A course that's 72.0/130 would have a bogey rating of (130/5.381+72.0) = 96.2. Then I took the Bogey Rating and divided it by the Course Rating to get the ratio. In this case, 96.2/72.0 = 1.34.

A CR of 74.4 with a Slope of 115 would be 1.29.

Here's what I found:

• One course had a 68.2/108 set of tees that came out to 1.29. All others were 1.30 or higher, and only 8 were 1.30.
• The median value (386/772) was 1.34.
• The highest value was 70.0/143, which came out to the only 1.38 on the chart.

Here's a count. As you'll see… most are pretty much in the middle.

Code: [Select]


1.29    1
1.30    8
1.31    36
1.32    101
1.33    184
1.34    229
1.35    153
1.36    45
1.37    14
1.38    1


Three examples of 1.34 courses:

• 74.0/134
• 66.1/120
• 72.7/132

Pine Valley off the senior tees is 71.9 and 150. I think low course rating and high slope means short and with all sorts of trouble just off the fairways. High course rating and low slope means really long, but wide open with no trouble. I don't think the latter makes for a particularly good golf course. Even if we sing the praises of the hard par, but easy bogey type places.

[Erik J. Barzeski]

My guess is that the Slope for Memorial will be HIGHER than for many of my other courses.

It doesn't appear to be higher.

I said here years ago that Bunkers are Overrated, and I'd guess that goes for how they factor into the Slope System, too.

Bunkers aren't given a lot of weight. The vast majority of a course's rating is simply length. Trees don't affect the rating or slope very much, bunkers, rough height, etc. It's almost all length.

Also, generally speaking, consider that "slope" is really just a second course rating, just done with a "bogey golfer" (a 20 handicapper, roughly) in mind. It's just math to get the actual slope. That's why when you look on the NCRDB, you'll find the Bogey Rating stated just like the Course Rating. Raters determine a bogey and a scratch rating, and use those numbers to get the rating (translates directly) and slope (math applied).

Michael, yeah, PV may be one of the most extreme outliers. Tobacco Road is kinda similar, but less so, as they have a 71.3/143 set of tees. Same idea - not that long, but LOTS of penal stuff. Also, it's going to be tougher to find the 74.7/110 type of course… because the bogey rating is pretty reliant on length as the baseline, and such a long course is also going to be long (even longer) for the bogey golfer.


P.S. Pine Valley: https://ncrdb.usga.org/courseTeeInfo.aspx?CourseID=3079

[Michael Felton]

I was surprised to see how low the slope at Walton Heath is. The Old is 75.7/135 from the purple tees. It's 7,462 yards from back there and the heather is hack it out sideways and the bunkers are pretty penal. Can't get much more than 120 yards out of them unless you get lucky and finish way in the back of them. The New is 74.8/131 from the purple tees again. That's about 7,100 or so. I would have guesstimated that both would be in the 140s based on the courses around me now that I know.

[Ken Fry]

Merion Golf Club:  Par 70, Course Rating=73.4, Slope=146


Kapalua Plantation Course:  Par 73, Course Rating=77.2, Slope=144

Even if there is no par, distance of holes will create one based on what a scratch player will shoot on average over 10 rounds.

The average golfer still has no idea what course rating and slope mean.  Many still have the '80's hangover that harder is better.  Didn't Golf Digest have a "resistance to scoring" rating to help support that belief??


We had a 1966 course that hadn't been re-rated in about 20 years.  When the rating team was finished, our course rating dropped by 4 points and our slope by 11 points.


When you have a private club in the US you're trying to entice people to join, this created a perception problem.  I won't claim it's right but saying it doesn't matter in a competitive market place is not accurate IMHO.


Ken

[Erik J. Barzeski]

I was surprised to see how low the slope at Walton Heath is. The Old is 75.7/135 from the purple tees.

Remember, it's the relative difficulty. Relative to the course rating.

A 75.7/135 course is still "more difficult" for a mid-handicapper than a 72.4/144 course… because the slope is just the slope of the line… with such a small difference (135/113 = 1.194, 139/113 = 1.23) in the slope of the line, it takes quite awhile to close the gap and cross over when the lines are "starting" 3.3 strokes apart.

Heck, plug the handicap index of someone in to the new WHS method for course handicap and you can see which courses are "more difficult" than the others.

9.2 * 135/113 + 75.7-72 = 14.7 = 15 CH
9.2 * 144/113 + 72.4-72 = 12.1 = 12 CH

Again, slope is the relative difficulty, but the course rating is the "baseline" or the "starting point" for the difficulty measurement.

[Tom_Doak]

In theory, Tom Doak's Memorial Park in Houston, where he eliminated a lot of sand in favor of other grass hazards that challenge pros a bit better, should be as good an example of a relatively higher course rating with a relatively lower SLOPE rating.  Has it been rated yet?

https://ncrdb.usga.org/courseTeeInfo.aspx?CourseID=4532

74.2/128
71.1/121
70.6/117

A sampling of the ratings/slopes from different tees. Nothing really out of the ordinary. 74.2/128 is a ratio of 1.32.

Well, that's kind of toward the low end of the scale.


I have to admit I've paid almost zero attention to this topic while building my courses, or afterward, but out of curiosity I looked up a few of my other courses.  The 128 Slope for Memorial Park is not an outlier for my courses:


125  The Loop
125  Dismal River (Red)
126  Ballyneal - with a 74.1 rating that's the lowest ratio of any of my courses, I think - maybe altitude is a factor?
127  The Legends (Heathland) - but only 70.0 rating


131  Old Macdonald - 74.4
136  Stone Eagle - 72.5
137  Rock Creek - 74.9


143  Pacific Dunes (!)
151  Sebonack - 77.3 course rating




The Slope rating of Pacific Dunes seems to be the outlier of the bunch to me.  I guess the amount of gorse in play is a big factor there.

[Erik J. Barzeski]

131  Old Macdonald - 74.4
136  Stone Eagle - 72.5
…
The Slope rating of Pacific Dunes seems to be the outlier of the bunch to me.  I guess the amount of gorse in play is a big factor there.

Old Macdonald is a "tougher" course than Stone Eagle (assuming both are par 72).

The lines don't "cross" until…

(x * 131/113) + 74.4 - 72 = (x * 136/113) + 72.5-72
x =~ 43 handicap index

That's where they cross and where Stone Eagle becomes the "more difficult" course - for a 43 handicap.

For example, an 18.0 index:

18.0 * 131/113 + 74.4-72 = 23.3 = 23 CH
18.0 * 136/113 + 72.5-72 = 22.2 = 22 CH

43.0 * 131/113 + 74.4-72 = 52.2 = 52 CH
43.0 * 131/113 + 74.4-72 = 52.2 = 52 CH

Remember, the slope is based on the starting point (the CR), and 1 slope point is only 1/113th of a "stroke" difference (multiplied by the handicap index, so for an 18.0, it's 18/113 of a stroke).

[MClutterbuck]

Courses should be aspiring to have a low slope rating, not a high one.  No one should want a course that is easy for good players and difficult for bad players.

That typically doesn't happen.

Typically, the rating and slope are pretty closely linked. I imagine you'd see an R^2 value that's pretty high if you plotted the slope versus the course rating for a large number of golf courses.

Like I said earlier (with different numbers, likely), you won't find many 74.7/112 courses or many 68.6/146 courses out there.

In other words, good luck creating a course that's hard for a good player but relatively easy for a bad player. I'm not even sure it's possible given how the ratings work.

Well, for starters you would have to eliminate all bunkers. Sheep Ranch rating might be interesting...

[Tom_Doak]

131  Old Macdonald - 74.4
136  Stone Eagle - 72.5

Old Macdonald is a "tougher" course than Stone Eagle (assuming both are par 72).

Actually, Stone Eagle is par 71 and Old Mac par 72 . . . not that I care much about which is "tougher".  For that matter, I had to think through the holes to remember what par was for either course. 


I am getting more like Bill Coore every day.  When I used to go visit one of his construction sites, I would ask how long a hole was, and he would reply, "I honestly have no idea."  I just meant whether the hole was a long par-4 or a medium 4 or a short par-5, but sometimes Bill wouldn't even commit to that!

[Chad Anderson (Tennessee)]

I had a course operator ask me to remove their course rating from our system because he felt it was too low.  He was worried golfers would look at the course rating and decide to not go play it because of a low rating.


I have never once looked at a rating before going to play a course.  I only see it when I post my score.


Does anyone use course rating/slope rating as a factor in deciding whether or not to play a course?

[Ira Fishman]

I had a course operator ask me to remove their course rating from our system because he felt it was too low.  He was worried golfers would look at the course rating and decide to not go play it because of a low rating.


I have never once looked at a rating before going to play a course.  I only see it when I post my score.


Does anyone use course rating/slope rating as a factor in deciding whether or not to play a course?

Never have looked. But I am pretty sure that some of the courses I avoid because of difficulty would have ratings and slope that would confirm my impression. Pine Valley is not very high on my bucket list for example.


Ira

[Erik J. Barzeski]

Does anyone use course rating/slope rating as a factor in deciding whether or not to play a course?

I have known guys to look for a “good” blend of yardage and CR to determine which tees to play.

[David_Elvins]

Erik,


If two courses have a course rating of 73 and one has a slope of 122 and one has a slope of 140, then the second course is 6 shots more difficult for a 36 handicap than the first course, whilst the courses play similarly for a 1 handicap. 


This is a significant difference in the architecture, if your ratio is not showing these two courses as being significantly different, then there is a problem with how you are presenting your data. 

[Erik J. Barzeski]

If two courses have a course rating of 73 and one has a slope of 122 and one has a slope of 140, then the second course is 6 shots more difficult for a 36 handicap than the first course, whilst the courses play similarly for a 1 handicap.

This is a significant difference in the architecture, if your ratio is not showing these two courses as being significantly different, then there is a problem with how you are presenting your data.

Had a bit more time so I wanted to elaborate a bit more.

73/122 is a 1.31, and the 73/140 about a 1.36. They're both towards the ends of the roughly bell curved distribution of ratios I shared from courses I had ready access to in the NCRDB. In fact, 1.31 is in the top <6%, and 1.36 is in the bottom <8%.

Obviously, there are some extremes. Pine Valley being a 71.6/150 (1.39 ratio) is among them (on the opposite side of the distribution).

And I would agree that those courses would present differently. My only point has been that extremes (like Pine Valley) are pretty rare, because the slope tends to go along with the course rating, and I went so far as to posit a mild correlation (R^2 value). I've also said that one must consider the course rating - difficulty as measured by slope is a relative difficulty, the starting point of which is the CR.

Here's the full graph. When I said the R^2 value would be "pretty high" before I thought it might be 0.6 to 0.65. Looks like - for these 772 sets of tees with a CR >= 65.0, the R^2 is nearly 0.7.


Again, too, that doesn't change the later point I was making: a 74.6/122 course will play "more difficult" for most golfers than a 70.3/133 course (assuming both are par 72). Those wouldn't "cross" each other until… roughly a 44.1 index. The latter course is not "more difficult" because of the slope for a 16 handicapper - the former is because of the CR. The CR is the "starting point" for the slope. In the y=mx + b formula, CR is "b."

[Bryan Izatt]

Just to try to make the rating system more understandable here is an analysis of two Doak courses that many are familiar with - Streamsong Blue and Pacific Dunes.  Tom expressed surprise that PD has such a high slope compared to many of his other courses.  Maybe this will answer that too.


I picked tees that were similar length at each course as that takes pure length (which is the very dominant factor in the rating system) out of analysis.  Turns out to be the Black tee in both cases.


Under the USGA rating system all longer courses will be more difficult for both the scratch and bogey golfer.  The longer course will also be relatively more difficult for the Bogey golfer compared to the Scratch golfer.  For each 100 yards added to the length, the course rating goes up 0.45 for Scratch and the bogey rating goes up 0.62 for Bogey. The distance rating is irrespective of any architectural features of the course.

Here's the basic information about the two courses, Black tee:



                                    Streamsong Blue                           Pacific Dunes


Yardage                        6698                                             6633

Scratch Rating               71.8                                             73.2

Bogey Rating                 96.0                                             99.7

Slope                            130                                              143



So, PD is marginally shorter, but 1.4 shots harder for S and 3.7 shots harder for B.  The difference between those two numbers accounts for why PD's slope is 13 higher using the USGA math.

The rating system is a two factor system - length and obstacles.

Length is very dominant and is based on effective playing length which accounts for changes due to non-standard roll, topography and wind.  For this analysis I assumed that neither course's length was materially changed by those factors. The rating system has a formula for calculating the length rating for both S and B.  Applying it to the two courses you get the following.  By subtraction the Obstacle rating can be obtained.  In practice in the rating process the evaluators measure a lot of stuff apply a lot of formulas and math to arrive at the Obstacle rating.  As you'll see below, the Obstacle rating is very small relative to the length.


                                    Streamsong Blue                           Pacific Dunes

Length Rating S             71.3                                             71.1

Length Rating B             92.6                                             92.2

Obstacle Rating S          0.5                                               2.1

Obstacle Rating B          3.4                                               7.5


Not surprisingly the length ratings for both Scratch and Bogey are very close. The slope based on length alone is around 114 - 115.  The difference in the Obstacle ratings account for the difference in the overall Slope.


The Obstacle Rating is based on 10 factors that are rated on a scale of 0 - 10 with 10 being the most severe.  There are guidelines in the rating system as to how to determine what score should be assigned to a particular factor for each hole on a course.  The 10 factors are topography, fairway, recoverability and rough, out of bounds, water hazards, trees, bunkers, green target, green surface, and psychological.


With both SS Blue and PD we can eliminate out of bounds and trees as relevant factors.  Topography is pretty similar too.


Fairways make PD tougher - they are significantly narrower than SS Blue.  SS Blue has enormously wide fairways for the most part - it's a much easier driving course.


Recoverability and rough is certainly harder at PD. The gorse is unforgiving and the rough next to the fairways.  At SS Blue you can recover from most places if you get off the enormous fairways.


They both have a few water hazards but the ones at 4, 11 and 13 at PD are probably more problematic than the ones at SS Blue


Bunkering is difficult at both but I'd guess there are more severe ones in play at PD.


I'm not sure there is a lot of difference in green targets between the two but I'd have to go through hole by hole to reach a judgement.


Green surfaces seem harder to me at SS Blue but there really probably not much difference between the two.


I find PD more psychologically challenging because of the narrower fairways and the ocean close to a few holes but this factor doesn't carry much weight.


More later on how you might game the system to raise or lower a course slope rating.

[Bryan Izatt]

As to how to game the rating system to increase or decrease slope without affecting the course rating, that requires increasing or decreasing the delta between the Scratch and Bogey Obstacle ratings. You can achieve that by changing some or many of the 10 obstacle factors. 


Keep in mind that a good portion of the Obstacle ratings depends on what features are in the Bogey landing zone around 200 yards and the Scratch landing zone around 250 yards.


If you want to raise your slope and not affect your course rating you could try some of the following.


Narrow the fairway and grow thicker rough around 200 yards from the tee.


Plant fir trees around 200 yards from the tee as they are harder to recover from.


Put  punitive bunkering around 200 yards from the tee that will be meaningless to scratch golfers.


Put punitive hazards around 370 yards from the tree on longer par 4's and on par 5's.


And, on and on........




Conversely, if you want to lower the slope and maintain the course rating you could widen the fairways, cut down the rough, remove bunkers and trees, all around 200 yards from the tee and near 370 yards from the tee on longer par 4's and par 5's.




For context, if you could change the rating of 3 factors by 2 points, say from 6's to 4's out of 10, you could decrease the slope by around 13. Changing three 4's to 6's would increase the slope by about 13.


Seems silly to me to pursue specific ratings or slopes when so few people have any clue about what they are about.




For whatever it's worth, I play 2 courses in Canada in the summer and 2 others in Florida in the winter.  My FL handicap index is a full 2 shots lower than my Canadian home one.  I attribute the difference to differences in the ratings of the 4 courses.  My Canadian ones are under rated in my opinion, but that handicap does travel well

[Kyle Harris]

131  Old Macdonald - 74.4
136  Stone Eagle - 72.5

Old Macdonald is a "tougher" course than Stone Eagle (assuming both are par 72).

Actually, Stone Eagle is par 71 and Old Mac par 72 . . . not that I care much about which is "tougher".  For that matter, I had to think through the holes to remember what par was for either course. 


I am getting more like Bill Coore every day.  When I used to go visit one of his construction sites, I would ask how long a hole was, and he would reply, "I honestly have no idea."  I just meant whether the hole was a long par-4 or a medium 4 or a short par-5, but sometimes Bill wouldn't even commit to that!

It's a damned miracle we got 36 (errr 37) holes out of you lot.