If you choose to read Mile Stamps, database records of the distances between mileposts between the start and end locations of the run will be replaced. You will always choose to read Mile Stamps from a 'master run', which is done expressly for the purpose of recording permanent track features, and in which mile boards are presumed to have been stamped with great care. If you are processing an ordinary data collection run from a territory where there has been an earlier 'master run,' you should probably choose not to read Mile Stamps. You would only do so if you have reason to believe that the mile stamps in the new run are more accurate than the milepost information currently in the database.
Whether you choose to read Mile Stamps or not, any mileposts stamped during a data collection run will be used to correct the location of the profiles gathered.
Caution: never read Mile Stamps if the odometer was out of calibration during data collection. Although scaled profile locations may be correct, the odometer error will affect calculations of rail inventory. It will also affect profile location when displayed as Reference plus Distance.