In-pipe localization of tools using time between signals

A system for estimating location of features in a pipeline, the system comprising:

• a device comprising a first array and a second array of electromagnetic sensors, the device having a cylindrical shape and sized to be deployed and travel in the pipeline, wherein the first array of electromagnetic sensors axially spaced apart from the second array of electromagnetic sensors by a distance;
• at least one processor;
• and
• a memory storing instructions that when executed by the at least one processor cause the at least one processor to perform operations comprising:
• acquiring measurements of signals from the first array and the second array of electromagnetic sensors;
• detecting welds in walls of the pipeline based on the measurements of the signals;
• calculating an average velocity of the device as the device passes each weld;
• estimating an instantaneous velocity of the device as the device passes each weld based at least in part by dividing the distance between first array of electromagnetic sensors and the second array of electromagnetic sensors by time elapsed between first array of electromagnetic sensors passing the weld and the second array of electromagnetic sensors passing the weld;
• calculating an error based on a difference between the calculated average velocity of the device traveling through the pipeline as the device passes each weld and the estimated average velocity of the device traveling through the pipeline as the device passes each weld;
• and
• estimating position of the device in the pipeline based at least in part on the estimates of the instantaneous velocity, the calculated average velocity, and the error of the device over time.