Longitude and Latitude
Geographic Coordinates:
Geographic coordinates are used to describe a specific location on a body of water. All nautical charts are based on this system.
Latitude and Longitude System:
This system is based on two sets of imaginary circles on the Earth’s surface. They are measured in terms of degrees.
-Prime meridian: Meridian passing through Greenwich, England. The maximum in either direction is 180 degrees. Parallels of latitude are measured in terms of how many degrees a given parallels is north or south from the equator. Each degree of latitude corresponds to sixty nautical miles.
Mercator Projection: The mercator projection is used to approximate the Earth's curved surface in two dimensions. It projects the Earth's surface features onto a cylinder wrapped so that the long axis of the cylinder is parallel to Earth's polar axis and the inner surface of the cylinder touches Earth's equator. A key feature that the mercator projection is that the meridians of longitude appear as straight vertical lines. They do no converge at the poles. The main advantage of charts that use the projection is that the geographic position of an object on the chart can be easily measured using the latitude and longitude scales along the border of the chart.
Geographic coordinates are used to describe a specific location on a body of water. All nautical charts are based on this system.
Latitude and Longitude System:
This system is based on two sets of imaginary circles on the Earth’s surface. They are measured in terms of degrees.
-Prime meridian: Meridian passing through Greenwich, England. The maximum in either direction is 180 degrees. Parallels of latitude are measured in terms of how many degrees a given parallels is north or south from the equator. Each degree of latitude corresponds to sixty nautical miles.
Mercator Projection: The mercator projection is used to approximate the Earth's curved surface in two dimensions. It projects the Earth's surface features onto a cylinder wrapped so that the long axis of the cylinder is parallel to Earth's polar axis and the inner surface of the cylinder touches Earth's equator. A key feature that the mercator projection is that the meridians of longitude appear as straight vertical lines. They do no converge at the poles. The main advantage of charts that use the projection is that the geographic position of an object on the chart can be easily measured using the latitude and longitude scales along the border of the chart.