A circle divided horizontally is the symbol for the Focal Plane of a camera, the actual point of focus. It is sometimes stamped on the back of a camera body in the appropriate space. The ( Focal plane indicator) is not something akin to a compass or speedometer- with movable parts. it is a reference mark. a Circle with a central Vertical Line- often used on Maps, generally means Latitude or observed latitude. Do not confuse with degrees. That"s my take.
On the London Underground map, the Circle Line is coloured yellow.
It looks like a straight central line going over a circle line, a small part of the map of the Underground.
A star is a capital and a circle is a city
Compass Rose
it means a capital
capital city
capital city
Compass Rose
The line, or I (Initialise) means on
It is a straight line that touches the circle.
If you mean a line that gous from the center of a circle to the edge of the circle, that is a radius.
a city