Datum shift ISO GPS

[[Da...]]

Hi true value seekers :)

I'm aware that Calypso is doing datum shifts only if needed, like Tom said -> viewtopic.php?p=33339#p33339
But where does this behaviour comes from?
Can anyone point me to GPS paragraph(s), telling why it shouldn't always use shift?
Currently less interested, but still - ASME paragraph?

[[Da...]]

ISO 2692 doesn't mention datum shift to begin with. A Maximum Material Requirement (MMR) on a datum adds to the Maximum Material Virtual Size (MMVS) of the Maximum Material Virtual Condition (MMVC).

It's similar to datum shift in ASME, but it has different rules when it comes to additional form, orientation or location specifications on the datums themselves. ISO 2692 does not require the user to decide when or when not to apply a "datum shift", it just changes the MMVC of the feature. How a software like Calypso handles that is a different story.

I think, Calypso thinks: "If the position is in compliance without using a bonus or a datum shift, then why not?"

And yeah, why not...


P.S.: As far as I can see, ASME also does not require the use or not-use of a datum shift.