We discuss two different methods of deriving ionosphere total electron content (TEC) from observations of Global Positioning Satellites (GPS) at Boulder, Colorado. In the first method, data from the National Institute of Standards and Technology Ionospheric Monitoring System (NIMS) are examined for the period of January 1994 to January 1995. In the second method, carrier phase models are constructed for four days in January 1995 and at two stations near Boulder. Both methods are compared with Faraday rotation values. Smoothed NIMS observations are an adequate representation for smoothed TEC variation during the day. Carrier phase models show good agreement with Faraday rotation and consistency between nearby receivers.¿ 1997 American Geophysical Union