The Position tolerance is the GD&T symbol and tolerance of location. The True Position is the exact coordinate, or location defined by basic dimensions or other means that represents the nominal value. In other words, the GD&T "Position" Tolerance is how far your feature's location can vary from its "True Position".
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GD&T Position Definition
GD&T True Position
Inspection of Position Tolerance using Boundary Method
External Exhaust Gas Recirculation
Position Control Tolerance : Geometric Dimension and Control
True Position Calculator
Inspection of Position Tolerance using Boundary Method
Position
Position Tolerance II