It is by using data on the apparent movement of the Sun in the Celestial Sphere that astronomers draw up maritime charts for navigators. For instance, to determine the latitude of a location on any given day of the year, a navigator needs to know the height of the noon sun on the ecliptic. So astronomers draw up charts of the incline of the Sun throughout the year, as shown in the chart below. According to the chart, on 22nd May, for example, the midday sun is on the vertical of the 16º N parallel. On the 7th November, the midday sun is on the vertical of the 12º parallel. The negative values in the chart refer to latitudes south of the Equator.