The geometrical frame moves in different directions and areas when its tolerance zones and (or)
location dimensions are determined in defferent ways. In this paper, by means of the measured coordinate
values of the toleranced features, vectors are used to study the translations and (or) rotations of the
geometrical frame, and further to judge if the errors are minimum and up to standard when the constraining
conditions are satisfied. The diameter of the minimum envelope circle of error is the value of the error
being searched. During translation and (or) rotation of the geometrical frame, if there are any the same
name vectors (SNV for short) on the envelope circle of error which envelops the measured elements, or,
in spite of SNVs , the envelope circle of error cannot be further reduced because of the constraint of the
reference, such an envelope circle of error is called the minimum one.
The results obtained show that 1 . the minimum envelope circle of position error can be found using
SNV technique; 2. on the circle there may be 4, 3, 2 even just 1 point because of the constraint of the
reference; 3 . the SNV technique can describe the change of the geometrical frame visually and is convenient
for on-the-spot technological analysis; 4. whether the geometrical frame has compensation of reference or
not, the position errors can be evaluated; 5. this technique is suitable for judging the measured results of
a hole group distributed on a rectangle or a circumference.