Wear trend calculations are a distillation of many thousands of individual measurements. As such, they are rich in the information required for scientific track management. However, the information coming out is only as good as the data going in. In order to achieve rail replacement projections that you can trust, it is important to ensure the highest possible quality of the data during collection, post-processing, and editing. The rail measurement system must be kept in calibration. Mileposts must be stamped accurately, and the accuracy of the odometer must be verified. Any remaining misalignment of curves must be corrected in the office. Bad measurements that could distort the averages must be weeded out. If the quality of the measurements is assured, the database becomes a rich informational resource, the value of which keeps increasing over time. If steps are not taken to assure the quality of collected data, you will find yourself with reports that you cannot trust, and an expensive measurement program that is difficult to justify.