It would be great to have an Tolerence-Parameter and Automatic Mode for the transformers Matcher and ChangeDetector, similiar to the LineOnLineOverlayer for example.
Espacially when you work with geographic coordinate systems (latlong) and data from different systems/formats is it hard to find a proper value for the vector tolerance. An Automatic Mode would help a lot.
best
Thomas
+44Hi Thomas,
This is an interesting idea. For some background reading, we have a couple of blogs: this on automatic precision, and this on change detection tolerance.
It’s important to note that the algorithms for overlays and change detection are completely different.
The overlay algorithm intersects data, and its automated tolerance is really to clean up any tiny imperfections caused by the intersection process. It’s a very, very, very small number, far below your data accuracy.
The change detection algorithm isn’t intersecting or otherwise altering the data. Because the data isn’t being changed, there’s no cleanup required and so no automated tolerance is required.
That’s not to say that we couldn’t create an automatic tolerance for change detection, I just think it’s not very likely. FME would need to know your data accuracy and/or the scale the data is intended to be viewed at - and I don’t know that FME could calculate that automatically.
Anyway, I don’t want to speak for our product managers or the geometry team at Safe, who will undoubtedly know more about this than I do. I just wanted to share some background into the algorithms and my thoughts on why FME might not be able to do this.
Regards
Mark
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