Nautical chart great circle routes. NOAA uses the polyconic projection for some of its charts of the Great Lakes, at both large and small scales. Positions of places shown on the chart can be measured from the longitude and latitude scales on the borders of the chart, relative to a geodetic datum such as WGS 84. A bearing is the angle between the line joining the two points of interest and the line from one of the points to the north, such as a ship's course or a compass reading to a landmark. On nautical charts, the top of the chart is
Longitude of the periapsis with part of it being measured in the plane of reference and the rest being measured in the plane of the orbit. Likewise, any angle derived from the longitude of periapsis (e.g., mean longitude and true longitude) will also be compound. Sometimes, the term "longitude of periapsis" is used to refer to "ω", the angle between the ascending node and the periapsis. That usage of the term is especially common in discussions of binary stars and exoplanets. However, the angle ω is less ambiguously known as the argument of periapsis. "ϖ" is the sum of the longitude of ascending node