The proof of guarantee comes from having two altimeters: one you can wear on your wrist and one mounted on the back of the airplane.
Definition of a Skydiving Altimeter:
An altimeter determines the height by the difference in air pressure. The higher you go the thinner the air becomes (resulting in lower air pressure).
A skydiver will zero his altimeter on the ground, and as the skydiver increases altitude the altimeter can determine the distance traveled by determining the difference in air pressure.
ALTITUDE IS GUARANTEED w/ appropriate conditions only.
a) Unexpected changes in tropical island weather
b) Strict FAA regulations (airport closures, flying restrictions, etc.)
c) If the Ultimate Tandem(14,000ft) cannot be reached you will only pay for the Regular Tandem(9,000ft). For prepaid customers you get a partial refund, if the jump is canceled you will get a full refund.
Skydivers "zero" out their altimeters for each Drop Zone they visit. If you skydive at sea level in Hawaii and then visit a Drop Zone in Colorado without adjusting your altimeter to zero you will have an inaccurate reading during your skydive. An altimeter that is not properly adjusted to zero might show your altitude as higher than you actually are which would not allow you the time/altitude required to open your parachute for a safe landing!
It is almost impossible to estimate your altitude with your eyes only and most experienced skydivers use additional audible altitude equipment next to their ears as a warning and as a backup for altitude awareness.
The wrist altimeter and the one mounted on the back of the airplane cannot be modified by an instructor during flight. The altimeter should read 0 (zero) before take off.
Some "Skydiving Clubs" force their tandem instructors to keep the indicator numbers on their altimeter hidden. They do not have an altimeter mounted inside the airplane that everyone can see. Because everyone in a skydiving airplane is seated facing the back of the airplane, we mount our altimeter on the back panel of the aircraft so that it is clearly visible to all.
Some altimeters have numbers that only go to 12,000ft. To see higher altitude readings, you have to count the continuing movement of the needle (example: for 14,000ft, the needle will circle around to the 12 then go past to the 2 which will translate 12+2=14000ft and so on). Please note that the numbers on the altimeter do not show the three 000's.
So BE WARY of a guarantee without proof. It's easy to say but not easy to prove!
If a skydiving "club" does not give the above proof and still asks you for a deposit, remember that by giving your money up front YOU MIGHT NOT GET WHAT YOU PAY FOR!
These "Clubs" often intentionally mislead their customers by abusing your lack of skydiving knowledge and preying on your anxiety before your skydive.
ALTITUDE IS MERELY THE MARKER OF YOUR EXPERIENCE! YOU'LL NEVER FORGET THE EXTREME FUN OF FLYING WITHOUT WINGS, LIKE A BIRD — LIKE PETER PAN!