0 an imaginary line between the North Pole and the South Pole, drawn on maps to help to show the position of a place -- 子午线，经线
This intersection is an arc of a great circle whose endpoints lie on this meridian.
At 35-deg eccentricity, the acuity asymmetry along the horizontal meridian was maintained with acuity for both significantly higher in the nasal retina.
Each half eye was halved again on the horizontal meridian.
Consistent with the physiology in cat retina, the periphery effect in humans also crosses over the ver tical meridian.
Representations of the zero meridians and the visual periphery were only clearly established for the lower visual field.
Figure 7 sketches a dome, a small patch is isolated by neighbouring meridians and parallel circles.
The observatory's orientation is linked to that of the heavens, with the principal axis of the tower aligned north-south following the plane of the meridian.
Each monocular zone corresponds to a 5-deg sector along the lower ver tical meridian, extending into the ipsilateral visual field.
