What is a yardage book?

A yardage book is a booklet with one page per hole. It is not equipment for very good players; it answers a question that comes up on every tee. Not how far it is to the pin, but what happens when the shot does not come off as intended.

WHAT IS IN IT

Each page shows the hole from above, the way you play it: the outline, the bunkers, the water, the green. With it come numbers at the places where a decision is made. How far it is to the near edge of a hazard and how far to carry it. How far to the front, middle and back of the green. How deep the green is, that is how much room lies between the front and the back edge. Whether it plays uphill or downhill.

The other half of the page is empty while the book is new. The player fills it in, and that is what the book is really for: what is printed holds for everyone, what is written in holds for him.

WHY THE DISTANCE TO THE PIN IS NOT ENOUGH

The number most people look for first is the distance to the pin. It answers exactly one question: how far it would be if the shot came off exactly as intended. It rarely does.

Every shot scatters, left and right and short and long, and the scatter grows with the length of the club. One intention therefore does not produce a spot but an area. The question that really counts on the tee is not how far it is, but what lies in the area you actually hit. If that is nothing but fairway and green, you can aim at the pin. If it holds a bunker, a pond or an out of bounds, the pin is the wrong target, even though the distance is correct.

A watch or a rangefinder will give you the distance too. Where the area starts to get expensive is something only a drawing can tell you, one that shows the whole hole and not just the line to the pin. That is why the booklet exists.

WHAT YOU WRITE IN YOURSELF

Three things, and none of them is in any dataset.

• Your own club distances. Not the ones from your best day, but the ones you normally reach. Without them every distance on the page stays a number; with them “148 left to the middle” becomes a club.
• Where you must not play. On most holes there is an area you cannot get out of in one shot, and it is often smaller than the whole dangerous edge. Marking it once in peace is a different thing from looking for it on the tee.
• Where the safe miss is. For every target there is a side on which a poor shot is cheap and a side on which it is expensive. Whoever wrote that down beforehand does not aim at the pin but beside it, and knows which side as well.

Then comes what only builds up over time: that the fairway tilts to the right, that the approach needs two more clubs in wind, that the left bunker is flat and the right one deep. A yardage book is therefore worth more after the tenth round than after the first.

HOW YOU USE IT ON THE COURSE

Before the shot, not after it. The page is opened before the club comes out of the bag: first look at the area you want to hit, then choose the target, then the club. After that the booklet stays shut.

After the round comes the second part, and it is the one most likely to be skipped: writing down what was different this time from what was on the page. A booklet that is not kept up goes out of date in exactly the places where it helped.

WHY PAPER AND NOT A SCREEN

Paper needs no battery, it does not glare in the sun, it survives rain better than most devices, and it can be added to with a pencil while you are standing there.

Then there are the Rules. The Rules of Golf restrict electronic aids; reading pre-printed distance and elevation figures is expressly allowed by Rule 4.3a, and deriving a club recommendation from them is just as expressly forbidden. What applies in detail is in the Rules of Golf and in the conditions of the competition, not on this page.

WHAT OPENYARDAGE BRINGS READY MADE AND WHAT IT DOES NOT

The drawing is ready made. It is computed from OpenStreetMap and carries, for each hole, what the data holds: outline, bunkers, water and green, the distance to the front, middle and back of the green, the depth of the green, the carry to the near edge of a hazard and over it, and, where an elevation model provides it, the height difference between tee and green. Choose a different tee and every distance is measured from there.

Not every hole has all of it. Where the data is missing the number is missing rather than estimated, and it is not an official survey either: for a counting round the club scorecard applies.

The rest you enter yourself. There are tools for the route, for areas that are out of the question, for trees, the out of bounds line, slope and for reference points with their distance to the front of the green, plus six note lines per hole, one of them headed NEVER, the club off the tee and five lines for wet, wind, dry, season and rough.

If you store your club distances, you can place a point in the drawing and get arcs there at exactly those distances, labelled with the club. The opening angle of that fan is set by hand and not measured: how wide your own scatter really is, this tool does not know. Nor does it work out a club from distance and elevation. The first would be an invented number, the second is forbidden by Rule 4.3a.

It prints as a stapled booklet, either 105 × 148.5 mm for your pocket or 105 × 178 mm for covers with a slot. All courses with hole lengths · To the app