Conflict?
There seems to be a conflict in computed values with another iPad app, Tide Graph HD, and I will continue to evaluate. I suppose the best way to check is to have both on hand and for any time and location, check the computed value against actual observations and then decide what is the best one for you to use.
If one does a comparison test, be careful as Tide Graph has more locations for a given general area vs the Wolfram app.
GigaPan about
Wolfram Tides Calculator