Latitude is a measure of north-south position on the globe. It is described as the angle between a position on the globe and the equator. At the equator latitude is 0o, whereas at the poles it is 90o North or 90o South. On a map these are shown as horizontal hoops around the Earth.
Water clock - For many centuries, the best technology available for keeping time was the water clock. While these clocks weren't always reliable they worked indoors, at night and on cloudy days, so in many ways they were more useful than the sundial, the only other clock in use at the time.