Originally Posted by munky
when i played a 9 hole course, it wouldn't give a round rating because it says there must be at least 12 holes. but what if there is duel tees? any way to play a round from each set of tees and get an 18 hole rating?
You can look up the course lengths on DGCR to get the total length, and then estimate the scratch scoring average (SSA) as:
(Course length/285)+1.67 * Number of holes
Then, to derive your personal round rating estimate, determine y as the rating-change-per-stroke, using x as the SSA:
For SSA's above 50.3289725:
y = -0.225067 x + 21.3858
For SSA's below 50.3289725:
y = -0.487095 x + 34.5734
Or you can just spitball it by subtracting or adding ten points per stroke above or below the SSA. For some more accurate spitballing, you can use ten points per stroke for a 50 SSA, and more like 13 points per stroke for a 44 SSA, and 6 points per stroke for a 68 SSA.
That should get you a reasonably close estimate for average vegetation and wind. I don't know for sure, but I think the PDGA app uses a formula much like this one to calculate round ratings for courses when tournament data is not available.
If you look the course up on DGCR, it has a calculator that implements this formula (with crude adjustments for vegetation) to automatically produce scratch scoring estimates on the course pages. So you might just be able to look it up there for each layout separately. I don't think they have a function for calculating round rating yet, but maybe if you enter your scores it does that. I don't know.
Another thing that might work is to go into the PDGA course directory and add that 18 hole layout for the course. If you can do that, then I think the PDGA app will pull that layout as a selectable option and produce round ratings based on whatever default formula it uses when there are insufficient tournament results for a layout to use tournament data. However, I just took a tour of the editing interface in there and, while it lets you add an alternate course length, there is no way I see to add layouts having different numbers of holes. It looks to me like you'd have to change the default number of holes to 18, which would make it provide inaccurate information about the course, and produce incorrect results for the 9 hole layouts.