Originally Posted by Hack2putt
so your're saying the one that measures gravitational pull on the ball can't be used unless otherwise stated in a local rule? ;-)
Using a device to measure anything (including distance) that can assist your play is a breach of Rule 14-3. There is no local rule possible to allow any such measurement apart from distance.
Exceptionally, Decision 14-3/0.5 allows a local rule to be made that permits the use of a device to measure distance only. If the device is capable of measuring anything else that could be useful in play, you cannot use it for measuring distance even if the other functions are switched off.
So, that means:
No local rule = no measurement of anything that could help you in your play.
Local rule in place = you can use a device like a GPS or laser range finder that can measure distance only. If the device is capable of measuring anything else that can help you in your play, you cannot even use it to measure distance.
In practical terms, for example, some laser rangefinders come with a with a slope measuring function and are therefore not legal for competition play;
it is likely that your iPhone/smartphone cannot be used for measuring distance because it has, at the least, gradient measuring capability.