I often receive questions from golfers wanting to settle bets about something they have experienced on the golf course.

I received one from a Lawyer who had an Engineering friend debating him over distance gained or lost hitting a 240 yd downhill Drive. He said:

"My position is that the downhill drive hurt my distance, because the angle of approach to the fairway was much steeper hence I get less roll and less total distance despite more ball flight time.
Aron (my attorney) takes the opposite position, that in fact the extra 40 yards in the air more than compensates for the distance lost because of the angle.

Can you settle this?"

Here was my response:

" I would agree with your engineer friend. In most cases, the downhill drop increases the carry by the greater amount than the steep angle of attack decreases roll after impact.

On a horizontal hole, roll is about 10-15% of carry. Let's assume 10%.

240 yd carry + 24 yd roll = 264 yd

On a downhill shot, a 40 yd drop would result in an additional carry of 30-40 yd, depending on the trajectory. The roll would be less, due to the steeper angle of approach. Thus, the distance would be:

240 + 30 yd carry + 15 yd = 285 yd.

Even if there was no roll, due to very damp fairways, the downhill drive would be longer. "

It's not always obvious to golfers that when hitting uphill, you need to hit more club and when hitting downhill, you need to hit less club. The question is how much more or less. Of course, it depends on many conditions. This page will discuss and deal with the effect of elevation changes alone (without wind, rain, cold, etc) so that you can improve your club selection and lower your score.

   

  The trajectory of a golf ball is now well understood. It depends on ball velocity, trajectory, and spin as well as on air temperature, humidity and density. Below is a graphic of the trajectory of a golf ball hit with a driver, 5-iron, and 9-iron.

Note that in the first part of each trajectory, the path of the ball steepens. This is due to the lift created by the spin of the ball. Note as well, that the trajectory of each is different at impact. The 9-iron's impact is the steepest and the Driver's impact is the least steep. Because of this, a Driver's range is more greatly affected by elevation changes than a 5-iron and the 5-iron's is more greatly affected than the 9-iron's. For every yard of fall, the Driver ball travels farther. If on a tee shot, for instance, the ball were to land 20 yards below the tee in elevation, it would travel horizontally 15 yards farther.

The graph above was produced using my projectile model for a 6-iron. The green horizontal lines represent placements of the golf hole's green, relative to the position from which the ball is hit. If the hitting position and green are at the same elevation, the ball lands at about 162 yards.

If hitting uphill to a green elevated by 20 yards, the ball lands on the green at a horizontal distance of about 141 yards. Thus, the effective distance of the 6-iron is 21 yards shorter.

If hitting downhill to a green, 20 yards below, the ball lands ont he green at a horizontal distance of about 180 yards. Thus, the effective distance of the 6-iron is 18 yards longer.

I've used my golf ball trajectory computer model to calculate the actual distances uphill and downhill shots play for all the various clubs. You can instantly download my report along with similar reports that explain how much wind affects your shots and how much slope affects your putts. Get them here. You can order the report on elevation changes for only $15.99 now for immediate download. Click on PayPal Pay button below.

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