[Ji...] Posted August 21 Share Posted August 21 Hello everyone, We are frequently encountering measurement‑related questions. Many junior customers keep referring to various international standards such as ISO standards. Our Calypso software has already been configured for ISO‑compliant evaluation. I would like to clarify: when evaluating the position tolerance of a hole, is Gaussian (least‑squares) fitting the default method according to ISO requirements? Which ISO standard and specific clause defines this rule? Link to comment https://qualityforum.zeiss.com/topic/27264-gdt-position/ Share on other sites More sharing options...
[Ma...] Posted August 21 Share Posted August 21 This is ISO compliant. Datums are tangential, but measured feature is Gauss. I think only difference about ASME and ISO will be in that feature's evaluation. 3 Link to comment https://qualityforum.zeiss.com/topic/27264-gdt-position/#findComment-154554 Share on other sites More sharing options...
[Ji...] Posted August 27 Author Share Posted August 27 Please sign in to view this quote. Sorry, I would like to know which part of the ISO standard defines this? I have searched for a long time but have not found any clear specification. Link to comment https://qualityforum.zeiss.com/topic/27264-gdt-position/#findComment-154812 Share on other sites More sharing options...
[Ma...] Posted August 27 Share Posted August 27 Please sign in to view this username. Hi and sorry, i have no document about this. But years on forum and work on machines can give a clue how it is. My main knowledge was with using ZEISS Inspect, where i can easily visually see how is ISO, ASME and GEOMETRY behaving. Many hints were from Please sign in to view this username. and his drawings and simulations. Link to comment https://qualityforum.zeiss.com/topic/27264-gdt-position/#findComment-154814 Share on other sites More sharing options...
[Jo...] Posted August 27 Share Posted August 27 You can have a look here for the applicable standards. https://dgq.de/fachbeitraege/iso-gps-matrix-modell/ Link to comment https://qualityforum.zeiss.com/topic/27264-gdt-position/#findComment-154816 Share on other sites More sharing options...
[Er...] Posted August 29 Share Posted August 29 (edited) From ISO 1101:2017 Please sign in to view this quote. Extracted integral feature: the real, tangible, non-perfect feature as probed by the CMM. Essentially the probed point collection belonging to that feature (a hole, a plane, etc.) Extracted derived feature: the feature computed from one ore more integral features. Examples are real (non-perfect, i.e. curved) median lines (centerlines) and median surfaces (like the median plane of a slot). Optionally, it is possible to specify that the associated (fitted) feature, for instance a Gaussian fitted plane or the perfect centerline of a Gaussian fitted cylinder shall lie inside the tolerance zone. If the Gaussian fitted element (feature) must lie inside the the tolerance zone, rather than the extracted element, this is indicated by adding (G) in the second compartment of the tolerance indicator. See picture below. In many cases, getting the Gaussian associated plane inside a tolerance zone is way easier than the extracted surface itself. So, answering your question, no, the Gaussian (least‑squares) fitting is not the default method for the the feature to be measured. By default, the extracted (real, probed, or calculated from probed points) feature must be measured. Edited August 29 2 Link to comment https://qualityforum.zeiss.com/topic/27264-gdt-position/#findComment-154974 Share on other sites More sharing options...
[Ji...] Posted September 1 Author Share Posted September 1 Please sign in to view this quote. If there is no G, and no other requirements, what is the default? Link to comment https://qualityforum.zeiss.com/topic/27264-gdt-position/#findComment-155044 Share on other sites More sharing options...
[Lu...] Posted September 1 Share Posted September 1 i dont have the standard but in AUKOM GDT AND AUKOM Level 2 datums are allways tangencial this is according the standard ISO 5459 that sould be as well activacted in calypso. i can provide some AUKOM slides and and you should consult this article!! This is a great article i recomend everyone read it https://www.xyzarchitect.com/blog/building-coordinate-systems-3d-measurements.html Link to comment https://qualityforum.zeiss.com/topic/27264-gdt-position/#findComment-155050 Share on other sites More sharing options...
[Ma...] Posted September 1 Share Posted September 1 Datums are always tangential: ASME and ISO Measured feature is: ISO -> Gauss / ASME -> tangential | unless it's specified otherwise Link to comment https://qualityforum.zeiss.com/topic/27264-gdt-position/#findComment-155052 Share on other sites More sharing options...
[Ji...] Posted September 1 Author Share Posted September 1 Please sign in to view this quote. Which ISO standard defines that? ISO1101-2017? ISO5459? ISO14405?? Link to comment https://qualityforum.zeiss.com/topic/27264-gdt-position/#findComment-155058 Share on other sites More sharing options...
[Ma...] Posted September 1 Share Posted September 1 Please sign in to view this quote. According to AI: i don't have those in hand to cite them. ISO 5459 - Datums and Datum systems ISO 1101 - features Link to comment https://qualityforum.zeiss.com/topic/27264-gdt-position/#findComment-155060 Share on other sites More sharing options...
[ni...] Posted September 1 Share Posted September 1 for datum ISO 5459 Annexe A for feature ISO 17450-2 (source copilot lol) Link to comment https://qualityforum.zeiss.com/topic/27264-gdt-position/#findComment-155062 Share on other sites More sharing options...
[Pa...] Posted September 1 Share Posted September 1 (edited) Please sign in to view this quote. ISO 17450-3, paragraph 5.1 Edited September 1 1 Link to comment https://qualityforum.zeiss.com/topic/27264-gdt-position/#findComment-155088 Share on other sites More sharing options...
[na...] Posted September 2 Share Posted September 2 Please sign in to view this quote. It's in ISO 8015:2011, paragraph 5.4, it may also appear in other GPS. The confusing thing is the naming in Calypso. I'm sure Please sign in to view this username. will ask Carl to explain it to us. Link to comment https://qualityforum.zeiss.com/topic/27264-gdt-position/#findComment-155154 Share on other sites More sharing options...
[ni...] Posted September 2 Share Posted September 2 i've donwload the : handbook ISO-GPS dimensionning (16/10/2025) (english or french) at https://cetiso.fr/livret-iso-gps/ updated about ISO 5459 2024 and ISO 14405-1 2025, may be not exhaustive but 92 pages of knowledge I wish i have had some years ago there is one line about datum tangential, and nothing about gauss on feature, but some pages about the differences beetween ISO and ASME, wish is often asked on this forum. good reading Link to comment https://qualityforum.zeiss.com/topic/27264-gdt-position/#findComment-155188 Share on other sites More sharing options...
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