Transmission line parameters play a significant role in a variety of power system applications. The accuracy of these parameters is of paramount importance. Traditional methods of determining transmission line parameters must take a large number of factors into consideration. It is difficult and in most cases impractical to include every possible factor when calculating parameter values. A modern approach to the parameter identification problem is an online method by which the parameter values are calculated using synchronized voltage and current measurements from both ends of a transmission line. One of the biggest problems facing the synchronized measurement method is line transposition. Several methods have been proposed that demonstrate how the line parameters of a transposed line may be estimated. However, the present case of today's power systems is such that a majority of transmission lines are untransposed. While transposed line methods have value, they cannot be applied in real-world scenarios. Future efforts of using synchronized measurements to estimate transmission line parameters must focus on the development and refining of untransposed line methods. This thesis reviews the existing methods of estimation transmission line parameters using synchrophasor measurements and proposes a new method of estimating the parameters of an untransposed line. After the proposal of this new method, a sensitivity analysis is conducted to determine its performance when noise is present in the measurements. / Master of Science