Our spacing is where we position the circle in the frames between point A and point B.
圓圈在A和B間的來回是我们的间距。
英语百科
Position circle
A position circle is a circle that can be measured both from a chart and from the surface of the earth for the purpose of position fixing. The circles can be measured by sextant. Two overlapping position circles can be used to give a position fix.