16/04/2019
In navigation, a rhumb line, rhumb, or loxodrome is an arc crossing all meridians of longitude at the same angle, that is, a path with constant bearing as measured relative to true or magnetic north.
When pilots want to fly a constant track direction, they’ll follow a rhumb lines (or loxodrome). Rhumb lines have constant bearings and cross all meridians at the same angle. ... A rhumb line on a Mercator projection is a straight line.
The effect of following a rhumb line course on the surface of a globe was first discussed by the Portuguese mathematician 🇵🇹Pedro Nunes in 1537, in his Treatise in Defense of the Marine Chart, with further mathematical development by British 🇬🇧Thomas Harriot in the 1590s, was an English astronomer, mathematician, ethnographer and translator who made advances within the scientific field.
Thomas Harriot was recognised for his contributions in astronomy, mathematics, and navigational techniques. Harriot worked closely with John White to create advanced maps for navigation.
A rhumb line can be contrasted with a great circle, which is the path of shortest distance between two points on the surface of a sphere.
On a great circle, the bearing to the destination point does not remain constant. If one were to drive a car along a great circle one would hold the steering wheel fixed, but to follow a rhumb line one would have to turn the wheel, turning it more sharply as the poles are approached.
In other words, a great circle is locally "straight" with zero geodesic curvature, whereas a rhumb line has non-zero geodesic curvature.
Meridians of longitude and parallels of latitude provide special cases of the rhumb line, where their angles of intersection are respectively 0° and 90°. On a north–south passage the rhumb line course coincides with a great circle, as it does on an east–west passage along the equator.
◗ RHUMB LINE
The Rhumb Line function allows you to compute the true course (TCrs) and distance (Dist) between multiple points (Lat, Long) .
Problem: What is the true course and distance between JFK (40 .6°, 73 .7°) and LAX (33 .9°, 118 .4°)?
Solution: Press the FLT key . Select the
Rhumb Line submenu .
Scroll to POINT: A Lat
and press CONV , to set the units to degrees (°) . UNIT
Next, press:
4 0 . 6 and tap enter to input 40 .6°
Lat, then
7 3 . 7 and tap enter to input 73 .7° Long for Point A . Then Scroll down to Point B
and press:
3 3. 9 and tap enter to input 33 .9°
Lat, then
1 18 . 4 and tap enter to input Long.
118 .4° Long .
The display will show 259° TCrs and 2,188 .57 NM Dist .
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