Note that Wikipedia gives longitude as degrees (always expressed as a positive number between 0 and 180) east or west of the Greenwich meridian. In contract, Google uses 0 to -180 to represent longitudes east of Greenwich, and 0 to 180 to represent longitudes to the west.
Thus New York City has a longitude of approximately 74 W, which would be expressed in Google Maps as -74. Twitter and DataSift both use the convention followed by Google.
Latitudes are expressed as degress north of the equator (0 to 90) or south of the equator (0 to -90).