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the tolelance of geometric shapes is showing how an angle can in different pryramids of triangles can be shaped
Datum dimensioning is where a single reference point is used for all dimensions in a single direction. E.g. If Point A is declared the reference point, then Points B, C, D, etc, will all be measured relative to Point A, not to each other. Chain dimensioning is where each point is measured to the next. E.g. Point B is measured from Point A, Point C is measured from Point B, Point C is measured from Point B, and so on. The problem with chain dimensioning is that each measurement relies on the accuracy of the previous measurement. If there is a tolerance associated with each measurement (+/- X), then the tolerance for each subsequent dimension accumulates and becomes the number of measurements times the tolerance of each measurement (+/- n*X). Since datum dimensioning uses only one reference point, the tolerances cannot accumulate as each measurement is isolated, rather than relying on the accuracy of the previous measurement. Common practice is to only use datum dimensioning in design drawings to ensure greater accuracy over the entire design without requiring tighter tolerances.
TOLERANCE STACKING: From: Page 347,Technical Drawing Book, Custom Edition of ITT-Technical Institute. Comment by A. Vives.
Positional tolerance is the total permissible variation in a location of a feature about its theoretically exact location with respect to the datum.
Zero Tolerance Laws allow for no exceptions. For example, Virginia's zero tolerance law is that if a driver under the age of 21 is pulled over and is found to have any, even a trace, amount of alcohol in their system, they will be arrested.