Watch the shadows. We know that the sunlight in lower Manhattan was coming from the east. The shadows, therefore, were pointing to the west. In the opening scenes the shadow of the camera is on the actors, meaning that we're viewing the scene from the east with the sun behind us. Then look at the background, the trees have shadows pointing to the left, meaning that left is to the west. So we're viewing that scene from the south looking north. From where in lower Manhattan can you look to the north and see a large grassy meadow with water and a shoreline beyond with a building skyline?
A collection of articles defining our times. The pages contain clickable links, don't let the titles fool you, some of the best articles have very non-descript titles and there are usually more articles on the matters in the days and week pages the links land on so it's a sort of treasure hunt through history, Enjoy!