Accurate position estimation of inline inspection (ILI) tools is critical if repairs are to be made to a pipeline based on survey results. Traditional ILI tools solve this problem by using odometer wheels in combination with above ground markers to provide estimates of inline distance and speed. For unconventional free-floating ILI tools, position estimation can be done without these. To accomplish this, correlations between onboard sensor data and known information about a pipeline and its environment are utilized. These correlations and how to apply them to constrain the tool position and speed towards the true values is discussed. A real-world example of this methodology demonstrating a verified location accuracy of within just a few meters is discussed.