Q. When I set the tolerance to zero, NoiseMap crashes (sometimes it just hangs forever).

A. Your input data has already divided the railway tracks into 10 m segments. Experience shows that NoiseMap will keep to the original 10 m tracks if you set the tolerance to a low value, say 0.1m. I suspect that if you set the tolerance to zero, then due to the precision with which decimal values can be stored in in binary values in the computer, there will be some values that can't be represented with zero tolerance. As a result, the curve-fitting algorithm will try forever to get an exact fit, which is unachievable. Hence the program appears to hang.

The answer is to set tolerances to a small value, say 0.1 m, and NoiseMap will stick to the original segmentation.