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Which distance is better, point to point distance or point to line ?pl explain why?

In 2D and 3D condition.

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Dan Mahoney • There really is no difference. The line has a central or centroid point that is referenced when asking for distance, so point to line is really a point to point distance.
The important factor is how does your software determine the distance. In PC-DMIS, I recommend 3D and choosing the "Perpendicular to" radio button. This will give a distance between the two points that is perpendicular to the surface vector the first point is on. If you choose "parallel to", it will give you the direct distance between the two points regardless of vector, essentially giving you the hypotenuse distance. So, be aware of the data your particular software provides.

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Pate Denney • Well... If your coordinate system is set up correctly you can can use point to point ... With that being said the blueprint should probably calling it out like that, which 99%dont. I use point to point for thickness' (spar wall thickness) in camio or modus. A point to line is different the line must be bound and remember the output will vary, depending on the length and position of line. It's all about the drawing though.
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William Morrison • I use Geopak so am not qualified to comment on any other software. I would think thought that on depending on the required tolerance this may affect your decision. If you pick a line that is irregular or not straight you may not get as true an answer as 2 local points. I guess the best advice is to determine how you would measure it by a more conventional method and try and replicate that condition on the CMM. Hope that helps. Cheers, Willy
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Allan Dulaney • Some softwares will allow you to choose along which axis for the distance, but yes, you should get a straight line distance either way, pt to pt or pt to line, unless you specify otherwise. If possible, it never hurts to verify with conventional means, calipers, height gauge, etc. Measure both ways on the CMM, then compare data with conventional readings. Where I programmed, no one believed the CMM (only when something was out of tolerance), so I always had to prove it by conventional means.
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Nelson Rigon • If you have a plane pt2pl will be better. Try do tests on a gage block.
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Jaison Samuel • Line to Line will give you a single value which will take a series of points and give the average value. If you need to give an official report it's better to take this method.
In other case like a tool correction we should go for point to point dimension so that we could know is there ia any deviation in the particular area.

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