It is not enough to detect an area of corrosion and reportit as such, an ILI inspection also needs to report the depthand extent of that corrosion accurately. The level of sizingaccuracy that can be achieved (POS) is usually stated as atolerance +/- a given percentage of the pipe wall thickness,and calculated to an 80% or 90% confidence level, meaning80% or 90% of all corrosion features will be expected tomeet the given tolerance.