 In this case the size of the hour marker ellipse is constrained by human height and the latitude of the sundial location, since the human gnomon shadow must fall on the hour marker ellipse to accurately indicate the time of day.Human gnomon analemmatic sundials are not practical at lower latitudes where a human shadow is quite short during the summer months.A 66-inch tall person casts a 4-inch shadow at 27 deg latitude on the summer solstice.