This was posted on the rec.sport.golf bulletin board by someone who was a member of a golf course rating team.
A USGA Course Rating is the evaluation of the playing difficulty of a course compared with other rated courses for the purpose of providing a uniform standard by which to compute USGA Handicap Indexes. A USGA Course Rating is equal to the average of the better half of a scratch golfer's scores under normal playing conditions.
The USGA Slope Rating reflects the relative difficulty of a course for players with USGA Handicap Indexes above scratch, compared with the difficulty of the course for a scratch golfer. If a course has a high Slope Rating it is relatively more difficult for the average golfer than a course with a low Slope Rating. Accordingly, under the Slope System, the average golfer receives more handicap strokes playing a course with a high Slope Rating than he does playing a course with a low Slope Rating. The standard USGA Slope Rating is 113.
A bogey golfer is one with a USGA Handicap Index of 17.5 to 22.4 strokes for men and 21.5 to 26.4 for women. A bogey golfer can hit tee shots an average of 200 yards [150 yards for women]. Bogey golfers cannot normally reach the green in two shots on holes exceeding 370 yards [280 yards] in length. A player who has a Handicap Index within these ranges, but is unusually long or short off the tee, is not considered to be a bogey golfer for course rating purposes.
A Bogey Rating is equal to the average of the better half of a bogey golfer's scores under normal playing conditions.
A Bogey Yardage Rating is the evaluation of the playing difficulty of a course for the bogey golfer based only on yardage.
Effective playing length of a course is the measured length corrected for roll, changes in elevation, forced lay-up and doglegs, prevailing wind and altitude above sea level.
Obstacle factors are features of a course that affect its playing difficulty.
Obstacle stroke value is determined for scratch and bogey golfers by totaling the ratings for each obstacle factor, multiplying these totals by relative weight factors, adding the resulting figures and applying that sum to a stroke conversion formula. The Scratch and Bogey Obstacle Stroke Values are added to the Scratch and Bogey Yardage Ratings respectively to obtain the USGA Course Rating and Bogey Rating. The Slope is the difference between the USGA Course Rating and the Bogey Rating multiplied by a constant.
A male scratch golfer is one whose proficiency is such that the better half of his scores will equal the average of the better half of the stroke play scores in the United States Amateur Championship. A woman scratch golfer is one whose proficiency equals the better half of the 64 players who make match play in the U.S. Women's Amateur Championship. The scratch golfer can hit tee shots an average of 250 yards [210 yards for women] and seconds shots an average of 220 yards [190 yards].
A Transition Zone is the area just beyond which the average distance a scratch or bogey golfer can be expected to hit with consistency. When the center of a green lies within this zone, the golfer has about a fifty percent chance of reaching the green, provided there are no punitive obstacles in front of the green. From the tee, it is ten yards deep; from the fairway ( for a second or third shot), it is twenty yards deep.
Rating is the evaluation of the playing difficulty of a course based only on yardage. It is computed by applying the effective playing length to the USGA Yardage Rating formula.
Because yardage is the predominant factor in determining a USGA Course Rating, accurate measurement of each hole is essential. We measure all new courses and any holes that have changed using laser measuring equipment. We usually will shoot from a spot in the middle of each fairway (for par 4s and 5s) to the center of each tee and to the front and back edges of the green. For Par 3s we shoot from the back of the green to each tee and the front of the green (note that this is slightly different that the USGA says, but it is quicker.) If there is a dogleg, we will try to measure at the turning point of the dogleg. On some Par 5s we will have to measure from 2 points in the fairway. From the first we measure to the tees and to the second, from the second we measure to the back and front of the green.
Once we have an accurate measurement of the course, we being to rate it. We usually start at number 1 and go around the course from tee to green till we reach 18. But, if the course is crowded, we will start on 18 and go from green to tee backwards around the course so as to not bother one or two groups excessively. We usually have a team of 3 or 4 experienced men (we only do the men's rating, there are separate teams of women to do their ratings). As we proceed along a hole, we only talk in facts about the hole and don't discuss the numeric ratings we are going to give the hole. We will measure items like the width of fairways in the landing areas, the width of the green ( and depth if we didn't measure the course that day) etc. Once we have completed looking at the hole, we will each compile our ratings. Then, one of us will read off our numbers and the others will state theirs and we will discuss, argue, debate, berate, poke fun at the numbers of others until we come to a consensus. The consensus is sometimes the average, but often it isn't as one side will convince the other of its arguments. The team leader is responsible for determining the final rating if a consensus can't be reached.
There are 10 obstacle factors that we rate the course on. In addition we modify the yardage based on the elements mentioned in the definition of Effective Playing Length. The obstacle factors are rated from 0 to 10 for both the scratch and bogey golfer. 0 means the obstacle doesn't exist (no water on a hole for example), 10 means that it is an incredibly difficult problem for this hole. They are expressed as a number for the scratch golfer and + or - value for the bogey golfer. So if the fairway was 30 yards wide on a 360 yard hole at the scratch golfer's landing area, but was 40 yards wide in the bogey golfer's landing area, rating might be 3 -1. So a 3 for the scratch golfer and a 2 for the bogey golfer.
The effective playing length numbers affect the length of the course. For example, it is assumed that a fairway of average firmness will roll 21-30 yards on a flat tee shot. If the fairway is very soft or uphill, you can lengthen the hole, if it was hard or downhill you can shorten the effective length of the hole. Other factors are doglegs or forced lay-ups that lengthen or shorten the hole (if it can be cut), a prevailing wind that blows primarily from one direction can also lengthen or shorten the course on certain holes (we don't worry if it isn't on an open course and from a constant direction), altitudes over 2000 feet cause the yardage to be shortened. We adjust the landing areas and the lengths of transition zones. Except for the changes in the shot distances due to altitude, we just note these factors and they are applied at the end of the calculations.
A) Topography - This is a factor if the stance or lie in the fairway is affected by slopes or mounds or the shot to the green is uphill or downhill. We will determine the stance/lie in the landing area to be one of 5 values: Level, Minor Problem, Moderately Awkward, Significantly Awkward, Extremely Awkward. There are drawings in the book to show us what they mean by this. Also we will determine how many feet uphill or downhill the green is from the approach area. Uphill has more effect than downhill (5 feet up = 10 feet down, 20 up = 30 down etc.). We use these to look in a table to determine the value. Level with a level green is 0, Minor with 10 feet uphill is 2 etc. We can adjust these upwards if the player can't see the green surface (+1) or the green is blind (+2). On Par threes only elevation counts (the tee is level).
B) Fairway - This reflects the width of the fairway where the players will be playing their shots and the problems around the landing areas. There is no fairway rating on a par 3. On holes over 200 yards, we modify the Recoverability and Rough factor for the difficulties the bogey golfer will have when their tee shot doesn't reach the green. So, we look at the length of the hole and the width of the landing areas. In a table we get a base number. For example, on a 340-379 yard hole with a 25-29 yard wide fairway we get a 3. For a hole of over 425 yards with a fairway less than 20 yards wide we get a 7. We can then adjust this upwards for either player for things like fairway width being reduced by a dogleg, contour or tilt, trees, bunkers, water or OB on one side or both; poor turf; or high rough. It can be lowered if there is little rough or you lay-up off the tee. In addition, there are +'s or -'s that can be applied to the bogey golfer's rating. If they can't reach the green in regulation and the additional landing area is small, if there is a long carry to the fairway and the rough is high etc.
C) Recoverability and Rough - R&R is the evaluation of the probability of missing the tee shot landing area and the green, and the difficulty of recovering if either or both is missed. The consequence of missing the green is considered to be about twice as significant as missing the fairway. Consideration should be given to the difficulty of getting the ball close to the hole with a shot from around the green.
The primary factors in R&R are the Green Target (more about this later) and the length and type of rough around the greens. Rough is divided into two types, Cool Season (rye grass, bluegrass, Poa annua) and Warm Season (Bermuda, Zoysia, St. Augustine, Kikuya and bentgrasses) Cool Season grasses of a given height are equivalent to warm seasons grasses about half as high. As an idea of the base values, a Green Target rating of 4 with a Cool Season Grass under 2 inches is a R&R of 2, while a Green Target of 8 with more than 4 inches Warm Season Rough is 9.
We almost always raise the values from the tables for R&R. If there are hollows or mounds, the green has large rises or drops around it, there is a narrow fairway we can raise the value. Also, if the Green Target for the Bogey golfer is significantly higher than the Scratch Golfer we must raise the Bogey Golfer's R&R.
D) Out of Bounds - The OB rating depends on the distance the OB is from the center of the landing area or green and if it is impractical/impossible to play away from it because of other obstacles, this is know as "obstacle squeeze". Rough over 6 inches in height is also considered to be OB for the purposes of rating. Also, lava, palmettos, desert, and heavy underbrush.
There is a table that uses the length of the shot and the distance from the center of the target to come up with a base number (i.e., full tee shot and 25 yards from center is a 6, < 90 [50] yards and 25 yards is a 1.)
Additions are for squeeze, elevated green with OB near it, hole tilts towards OB, cart path near OB, OB on left for Scratch or right for Bogey. Subtract for OB protected by Trees, Wall, Fence, also if you can play way without other problems.
E) Water - The rating for water depends on its distance form the landing area or green and, in the case of a hazard crossing a hole, the problem involved in playing over the hazard. If a water hazard closely surrounds more than half of a green, it is also rated under R&R. If a water hazard forces a player to lay up, it is also be rated under Dogleg/Forced Lay-up. A hazard that is deep and can't be played out of is rated more difficult than one you can recover from.
There is a table that determines the basic rating based on the carry distance for crossing water hazards or the shot length and the distance from the center of the Target Landing Area for lateral hazards.
If there is more than one hazard or it is in play more than once, we take the higher table value and adjust upwards. If the hazard is within 10 yards or the green or surrounds it we also go up. Points are added if the ball can be deflected towards it by a cart path, tilted green or fairway. If it is very narrow, or dry most of the time we subtract.
F) Trees - Trees are the most contentious rating of all. The rating is fairly vague and open for debate. Basically, you evaluate the number of trees, the size of them, the probability of recovery and the distance from the center of the target to get a value from a table. Longer holes get points added, especially if the trees are in play more than once. Par 3s have 2 subtracted from the table value.
G) Bunkers - Generally, bunkers are rated according to the size proximity to the target areas. First we have to determine the Green Target Rating. From it and the amount of green closely bordered by the bunkers we get the base rating. Then, we can adjust upwards for deep bunkers, tight landing areas with bunkers, pot bunkers, bunkers behind greens that slope severely forward, hardpan or pebbles in the bunkers. We adjust down for shallow bunkers, no fairway bunkers, etc. Par 3s get reduced one.
H) Green Target - The green target is an evaluation of the difficulty of hitting the green with the approach shot. Primary considerations are target size, length of shot, how well the green holds and the difficulty of normal hole locations.
Basically, we determine the approach shot length for both the scratch and the bogey golfers. For example on a 420 yard hole, the scratch golfer hits his tee shot 250 yards so his approach shot length is 170 yards. The bogey golfer hits his tee shot 200 yards and his second shot 170 yards so his approach shot is 50 yards.
We then determine the effective diameter of the green. If the green is basically round or elliptical, we just measure the width and length and average them for the diameter. If the green has multiple sections, we can use the "Circle Concept" to determine the green diameter. This consists of finding a group of small circles that cover the sections of the green and then adjusting the diameter to reflect the average of these weighted by the percentage of the time each portion is used. For example, if we had a green with a large section that was 26 yards in diameter and small section that was 12 yards in diameter and the small section was used 25% of the time, the effective diameter would be (26*3+12)/4 = 23.
Using the diameter and the length of the approach shot we look in a table for the basic rating. If the case above (420 yard hole and 23 yard diameter target) we would get a rating of 5 for the scratch golfer and 3 for the bogey golfer. So, this is a 5,-2 green target. In other words, it is an easier target for the bogey golfer because he can't reach it in two shots which makes his shot to the green much shorter. The minimum rating for green target is 2.
We can add points for the green being firm, crowned or multi-tiered (if we didn't reduce the diameter because of this tiering), sloped to the back, elevated or hidden by bunkers. We subtract for a soft green, a slow, forward sloping green, or one that you can roll on to.
If the hole distance falls in the transition zone area, we determine the green target for both the long and short shots and average them.
The Green Target is then used for determining R&R and Bunkers.
I) Green Surface - Basically, we look at the contouring and slope of the green and the speed of the green (measured with a stimpmeter) and look up the value in the table.
J) Psychological - If there are 3 or more obstacles with a rating of 5 or higher and the total of their points is 20 or more we assign a psychological rating. Also, the first and last holes automatically get ratings of 2 or 3. The number of highly rated obstacles and the total of their points are the indexes into a table of values.
Once all this has been rated, the numbers are entered into a computer and the ratings are determined. Each of the obstacle factors is totaled for all Par 4 and 5 holes and separately for all Par 3 holes. These totals are then multiplied by a weight. For example, the weight of Topography on Par 4/5s for the Scratch golfer is .10. For the Bogey golfer it is .12. On a Par 3 it is .08 for both. The total of all the weights is 1.00 for Par 4/5s and 0.80 for Par 3s because they are deemed to be only 80% as important. Finally, these figures are all totaled for both the Scratch and Bogey golfers.
Effective Playing Length (EPL) is then calculated by adding the following to the measured course length:
The Scratch Yardage Rating is (SYR): EPL/220 + 40.9
The Bogey Yardage Rating is (BYR): EPL/160 + 50.7
The Scratch Obstacle Stroke Value is (SOSV): (Sum of weighted obstacles)
* .11 - 4.9
The Bogey Obstacle Stroke Value is (BOSV): (Sum of weighted obstacles) *
.26 - 11.5
The USGA Course Rating then is:
The Bogey Rating is:
The Slope finally is:
So, if you want to know what the bogey rating for a course is:
So for a course with a slope of 137 and a course rating of 72.3 the bogey
rating is 97.8.
For a course that is 113 and 72.0 it is: 93.0. And for a course that is 95
and 68.5 it would be: 86.2.