Or the sun's azimuth , that is the direction in the horizontal plane to a plumb line dropped from the sun. Altitude and azimuth both depend on the date, as you can see in the graph above. Hence, in both cases the date has to be taken into account in some way or another. The altitude principle is handy for portable dials, as one doesn't need to know where north is. They should simply be aimed at the sun.
Examples are the ring dial and the shepherd's dial .
This site doesn't have examples of these. Altitude dials have the disadvantage of being inaccurate around noon, as the sun's altitude changes little there. The analemmatic dial utilizes the sun's azimuth. The gnomon is a style that is perpendicular to the dial face. In the specimens presented here the dial face is always horizontal and the style vertical.