Differece between a mile in land and a mile in ocean?

Answer 1

Nautical Mile (mile in ocean):
The nautical mile was historically defined as a minute of arc along a meridian of the Earth. It can therefore be used for approximate measures on a meridian as change of latitude on a nautical chart.

The derived unit of speed is the knot, defined as one nautical mile per hour.

One nautical mile converts to:
1.852 km (exact)
1.150779 mile (statute)
2025.372 yard
6076.1155 feet

International mile (mile on land) :
It converts to in international units as:
1609.344 m
1.6093 km

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Answer 2

the difference is 780 feet.