The nautical mile and astronomical navigation

The nautical mile and astronomical navigation: In navigation and aviation, especially at sea, the nautical mile is used as a unit of measurement. It is equivalent to one minute of angle along a meridian on Earth.

nautical mile. Author image user: Yodin
Giant ocean wave. Author image: Unknown

The nautical mile and astronomical navigation:

They define it as one minute of arc measured along any meridian.

The nautical mile and astronomical navigation, image one nautical mile on latitude scale

In terms of distance, a nautical mile is equal to 1,852 kilometer.

People commonly use it to measure distances at sea or in the air.

The use of NM, the internationally agreed-upon measure of one nautical mile, which is exactly 1.852 meters, remains in place today


The nautical mile and astronomical navigation, image flying fish
Flying Fish. Author image: Mike Prince from Bangalore, India

The nautical mile and astronomical navigation:

The nautical mile and astronomical navigation

In fact, envisioning the Earth halved simplifies the calculation since the NM derives from Earth’s circumference. (40.000 km)

After dividing the half-circle into equal portions of 360°, one can further divide these degrees into 60 minutes.

Classic explanation
The nautical mile and astronomical navigation, image definition NM

Within navigation, one of these minutes (also referred to as minutes of arc) along a great circle on Earth represents a single NM.

overall, nautical charts employ one of three map projections: the gnomic, polyconic, and Mercator.

Among these three, the Mercator projection takes precedence as lines of latitude and longitude intersect at right angles, creating a rectangular grid.

In fact, this grid enables users to plot straight lines of latitude and longitude as direct courses easily for navigation purposes.

The nautical mile and astronomical navigation:

On this website, we explore creating a simplified plotting sheet inspired by the Mercator concept

Indeed, incorporating the NM, which represents one minute of latitude, greatly simplifies navigation in open water.

Consequently, it assumes a vital role in exploration, shipping, and geography, contributing significantly to these fields.


The nautical mile and astronomical navigation, image Artic sea
Arctic Sea fog at Garths Voe. Author image: John bateston

Difference between a nautical mile and a knot. NOAA