Caddie's Role: The modern professional golfer takes for granted he will have a yardage book at his disposal no matter where he plays. At the upper end of golf it is the caddie's responsibility to provide accurate distances today.

The caddie of 20 years ago made his own distance chart. The book was in keeping with the times. Every green was round and every fairway arrow straight. There is probably more information in a decent sized par five today than there was in the whole front nine of a handmade book from the early 80s.

There was not so much emphasis on precision, golf was more reliant on feel than numbers back then.

Jack Nicklaus was credited with being the first modern pro to use yardage consistently. I'm sure there were others before him, but it obviously didn't help them as much as it did Nicklaus. His profile made him the pioneer of yardage.

With the evolution of number information based on individual paces and rope measurements, if there was water to negotiate, to the more advanced measuring wheel and on to today's hi-tech laser measurements, the process has progressed rapidly from seat of the pants to scientific in the space of a couple of decades.

Given the accuracy of the better professionals there is no doubt that the numbers we provide them with need to be precise. Some pros carry four wedges which cover distances in increments from 80 to 125 yards. The difference between two or three yards for an accurate professional with a sandwedge in his hand is very noticeable. When you consider such precision it is easier to understand how such low scores are shot so frequently.

It is not just the top golfers that demand such accuracy. Last week in the north east of Spain myself and another caddie were busy with our annual yardage-book making stint.

The Tour School Pre-Qualifying takes place next week over three courses. We were taking advantage of a caddie break to get three books ready in the space of a week. The task would be virtually impossible within this time frame without two people working together .

With only 36 players getting through from this stage to have a go at final qualifying out of 240 starters, the hopefuls must shoot low. Accuracy may well be more important at this level.

Most of these "school" players will undoubtedly have been raised on yardage. They will take it for granted as much as they would expect a well struck drive to go well over 280 yards.

Not many would actually know what goes into producing a yardage book. Just as they probably wouldn't know what technology has produced the excessive drives they consistently expect to hit. Why should they? They are golfers not engineers.

In fact the modern caddie would not know what goes into making the books they rely on so heavily. Like his boss the modern caddie has been spoon-fed numbers, he can afford to pay someone else to compile the necessary information for him. The more diligent person will use the yardage book as a basic guide and add more relevant numbers according to their player's demands.

In the interest of quicker play the European Tour likes to have the measurements taken from obvious landmarks in the middle of the fairways. Whoever makes the yardage book, with the consent of the Tour, uses spray paint to mark dots on the fairways.

The old-fashioned way of using trees and bumps on the fairways leads to confusion and eventually mistakes. We use a water-based paint that disappears totally within a couple of weeks and does not burn the grass. The dots are traditionally yellow, red and a yellow star set from 240 to 300 yards from the tee, unless there is an unusually short par four.

The first thing to do when embarking upon such a task is to get up early and be ready to paint at first light, so that you get ahead of the bus load of enthusiastic Swedish amateurs who tend to mob the golf courses of the north east corner of Spain at his time of year. Off we go, one heavily armed with cans of spray paint, a laser and two reflectors. The other has his sketch pad and pencil and a fading memory of first-year art class. While I am giving my very personal impression of the golf course, my colleague is zapping from the dots to the reflectors at the front of the green and the back of the tee .

The sketcher draws the greens and the undulation on and around them, with bunker and water carry numbers. The idea is that the player has an accurate number and picture of where he is trying to hit the ball to. The decision making should, in theory, remove a large part of the risk in the shot played due to accurate distance and visual information.

A compass is marked on each hole and if it is a dog-leg, two compass points will be given. Some books will provide elevation indicators and the incredibly accurate ones will give a precise grid system on the green. This way if, say, the pin is given as 21, five right it will be instantly recognisable in relation to the particular greens contours .

When all the marking and sketching is made, the drawings must be transferred to a master sheet, photocopied, cut and compiled. Conversions have to be calculated of every number provided and transferred into metres these days as probably half the field will want to work in metres.

There is a point, of course, where the information provided may be well beyond the average pro. Just like numbers are largely irrelevant to the average amateur because they are not aware how far they hit each club to start with.

There can be a danger of paralysis by analysis with over information, but in general the standard of yardage book provided to the modern pro is very user friendly.

Whether the yardage book users can match the accuracy of the numbers with an equally accurate shot is another question.