Why doesn't my gps work in New York?

So I was in New York a few days ago and when I was in Manhattan I tried to get to times square. My cars gps, my galaxy s4 gps and my friends iphone had the same problem. The gps would tell me to go the opposite route then halfway go another direction. Could this problem happen because I was roaming? Or is new York that big that it causes gps's to break?

GPS can be sporadic! I was in Mexico earlier this year and could not get a gps signal anywhere.

To operate properly a GPS receiver must have at least four GPS satellites in sight. That is often difficult in "urban canyons", i.e. In streets surrounded by tall buildings, which is largely the case city centers like Manhattan. Less satellites (3 is the bare minimum) lowers the accuracy of the positions your device computes.

That said, an in-car GPS (i.e. Built-in) is connected to more devices such as the odometer (to track your actual speed) and gyroscopes (to track direction and changes) that enables it to continue giving directions even when no GPS signal is available.

Also GPS-computed locations come with inherent inaccuracies that get larger if few satellites are available. In dense urban areas, it is common for your GPS device to think it is on the wrong street and so give you incorrect directions.

The tall buildings can make it difficult for your GPS to connect with the necesary satellites. When that happens, the GPS usually has your location wrong and then gives wrong directions.