Just minutes into the picture, Breslin finishes a phone call: he hangs up, and is just exiting the booth when we hear the distinct sound of a coin hitting the coin return slot and NOT falling into the phone company coin bin, as it would if the person had made a successful outgoing call.
To locate their position, they are pointing the sextant to the polar star.
When they got the partial result "latitude: 30 degrees", they are still
wondering if it is the northern or the southern hemisphere. However, since
you cannot see the polar star from the southern hemisphere, it is
quite obvious on which hemisphere they are.
Urban legend presented as fact: Breslin deduces which hemisphere they're in based on which direction the drains flow. This effect, known as Coriolis force, is quoted by Breslin as causing moving objects on the surface of the Earth to be deflected in a counter-clockwise rotation in the Northern Hemisphere and in a clockwise rotation in the Southern Hemisphere. It is not effective on water drainage, so it cannot be used to scientifically and surely determine in which hemisphere one is.
Javed uses a sextant from an enclosure that is open to the sky but has walls on all four sides. Using a sextant is contingent on being able to see not just the sky but also the horizon which Javed can not do from his position, therefore this would not have worked.
When Rottmayer first meets Breslin, Breslin introduces himself as his cover name, Anthony Portos. Rottmayer says, "The fourth Musketeer." Porthos (different spelling) was actually one of the 3 Musketeers in Alexandre Dumas' famous novel. D'Artagnan was the 4th musketeer.
The goof item below may give away important plot points.
Towards the end, when Ray hangs from the ladder after the explosion, the helicopter takes off to the right. On the water there are still ripples from the downdraft from the helicopter even though it has flown away.
When the chopper arrives to pick up Breslin and Rottmayer, the ammo belt in the machine gun keeps disappearing/reappearing. When the chopper first arrives, you see the shiny brass of the cartridges, then when Rottmayer grabs it to shoot the guards, the brass disappears even though he is clearly "firing." When he hops back into the chopper and replaces it on the mount, the brass reappears. From there, it makes one more disappearance as Rottmayer drops the gun to Breslin before coming back for the rest of the scene.