Subject: How far to travel to equal 1 ft. drop in elevation?

Since the Earth is round, how far would a person have to travel 
horizontally to equal a one foot drop in elevation?  In case I'm not 
asking the question properly, imagine this: a beachball with a 
yardstick laying on top of it.  How far out along the yardstick (from 
where it touches the top of the ball) would you have to travel to 
equal a one foot difference between the yardstick and the surface of 
the ball? (substituting the Earth for the beachball, of course).  
Thanks, Mike

Re: How far to travel to equal 1 ft. drop in elevation?