Talk:Rhumb line

Diagram

Please consider using this diagram in the article. — Preceding unsigned comment added by Kpjas (talk • contribs) 08:21, 4 July 2004 (UTC)

Azimuth and latitude?

I guessed you need longitude and latitude for both of the points the loxodrome should connect. Azimuth is only another word for latitude, isn't it? --85.74.3.188 10:13, 11 Apr 2005 (UTC) (de:Benutzer:RokerHRO)

No, azimuth is another word for bearing or direction. ~Kaimbridge~ 15:30, 12 October 2005 (UTC)

0, 90, 180, 270 degrees are not considered a rhumb line or loxodrome

0, 90, 180, 270 degrees are not considered a rhumb line or loxodrome, also the definition is that is cuts ALL meridians at a constant angle. It should be more clear that these are not rhumb lines or a loxodrome, rather then just being exceptions. I know this is true for a loxodrome, I'm unsure if this is specific to a loxodrome.

90 and 270 might be as they do cut at a constant angle, I remember reading somewhere these are still not loxodromes.

--Ant 18:31, 6 January 2006 (UTC)

sorry,but 0,90,180,270 degrees are considered as rhumb lines well it is very famous that the equator is both a great circle and a rhumb line so are other latitudes and longitudes since they have a constant true direction they are considered as rhumb line — Preceding unsigned comment added by 71.42.38.195 (talk) 06:21, 6 October 2007 (UTC)

It all depends on what your definition of Rhumb Line is. If your definition is that which is commonly found in professional navigational sources, then...

Rumb Line   A line on surface of the earth making the same oblique angle with all meridians, then yes, Anthony is correct and the bearings 0°, 90°, 180° and 270° can not be true rhumb lines, since those headings fail the "oblique angle" test from the above definition. The source for the above definition is the: American Practical Navigator, 1966, published by the U.S. Naval Oceanographic Office, and in continuous print for over 200 years and commonly referred to as the "Bible" of navigational data, methodology, definition and history. It is found on every ship of the U.S. Navy. However, less precise definitions, like those often found in common dictionaries (and unfortunately, in this Wikipedia article, as well) fail to include the "oblique" angle distinction. As for me, I'll stick with the professional navigators when it comes to questions of meanings of their own language that they evolved for hundreds of years of practical usage. Boot (talk) —Preceding comment was added at 22:40, 6 May 2008 (UTC)

Wrong. A rhumb-line, or loxodrome, is a line on the surface of the Earth that makes a constant angle with all meridians, period. No exceptions. All parallels and meridians are rhumb lines. -- Alvesgaspar (talk) 01:46, 19 January 2009 (UTC)

Can anyone suggest a practical or intellectual reason for excluding the four special directions? is there any significant difference in principle between a rhumb-line that cuts the equator at zero angle and one that cuts it at one second of arc? — Preceding unsigned comment added by 62.30.56.245 (talk) 22:05, 19 October 2009 (UTC)

One workaround to the issue of different definitions is to include both with an explanation of each for how/why they vary. HarryZilber (talk) 14:29, 21 October 2009 (UTC)

A rhumb is a compass bearing. A rhumb line is the line (straight line on a chart, curve on a globe) you get by following a rhumb. Meridians and parallels are clearly rhumb lines. –jacobolus (t) 16:14, 19 May 2023 (UTC)

Old maps

I found the section about old maps a little confusing. Would I be right in thinking the maps in question were *not* using a mercator projection? 195.137.91.247 (talk) 01:00, 19 January 2009 (UTC)

Article structure

While I haven't reviewed the MoS, it appears to me that the section Etymology and historical description is positioned way too far down the page. My thinking is the article would work better with that section further up, perhaps prior to == Usage ==. The paragraph can also be rewritten to account for the two different definitions noted above. Comments? HarryZilber (talk) 14:29, 21 October 2009 (UTC)

Pros and cons

What are the advantages and drawbacks mentioned in the opening paragraph? The article seems to make no further mention of them. 89.240.7.86 (talk) 12:09, 14 February 2010 (UTC)

I agree — Preceding unsigned comment added by 86.134.252.154 (talk) 09:05, 5 July 2012 (UTC)

Material deleted

I have deleted the following section:

"Unlike a great circle route, which is the shortest distance between two points (for which the bearing of travel is not constant), following a rhumb line requires continual changes in the track of the vehicle to maintain a constant course. In theory this occurs more and more sharply when approaching the North or South pole."

Firstly, the assertion "...following a rhumb line requires continual changes in the track..." is potentially confusing. A loxodrome is, by definition, a line of constant bearing.

Secondly, loxodromes (rhumb lines) are not used for practical navigation in polar regions.

Dulciana (talk) 18:50, 6 July 2010 (UTC)

Having a "continual changes in the track" is probably referring to a property of geodesics which are locally "straight", that is has zero Geodesic curvature. If you were to drive a car along a geodesic you would hold the stearing wheel in the centre, but to follow a loxodrome would require turning the steering wheel. This is the property I thing is being referred to. Which is an important one.--Salix (talk): 00:34, 7 July 2010 (UTC)

That was how I understood it also. —Mark Dominus (talk) 04:00, 7 July 2010 (UTC)

Okay, agreed that "continual changes in the track" along a rhumb line could be considered correct, but to a navigator it sounds hilariously wrong. To a navigator, someone traveling along the 89th parallel, circling around the pole, is on a constant "track" of 90 or 270 degrees. Tim Zukas (talk) 01:13, 30 August 2010 (UTC)

Usage

The North American Muslims part of this article (in "Usage"), and maybe other parts, seem to be taken directly from "The Math Book" by Clifford Pickover, page 116. 208.65.162.142 (talk) 01:27, 6 September 2010 (UTC)

Which circles are loxodromes and which are not on a sphere

I found a very interesting discussion above. First of all a loxodrome is not limited to the spherical surface. As regarding to the spherical loxodromes, the equator can be derived from the equation (system of equation) of the loxodrome. Also any meridional circle can be derived from it. However, as far as I know, the equation of other parallels besides of the equator cannot be derived from any form of the loxodrome's equation. So I would say, that the equator and the meridians on the sphere loxodromes are.Theodore Yoda (talk) 18:48, 11 April 2013 (UTC)

Zero geodesic curvature?!

There is a section which reads "If one were to drive a car along a rhumb line one would hold the steering wheel fixed, but to follow a great circle one would have to turn the wheel, turning it more sharply as the poles are approached. In other words, a rhumb line is locally "straight" with zero geodesic curvature, whereas a great circle has non-zero geodesic curvature."

How is this correct? A great circle on a sphere is a geodesic, so it has zero geodesic curvature on the sphere. The great circle is precisely what you get when you drive in a straight line. The rhumb line does NOT have a fixed steering, just look at the path near the poles where the steering increases (if you're approaching the pole) ever higher. At the equator the direction of changes, it is a point of inflection. Clearly the 'amount of steering' is massively different from the equator and the pole, even in the diagram. AlphaNumeric (talk) 11:34, 18 December 2017 (UTC)

Good catch! This was a change just yesterday by an anonymous editor, in two places swapping rhumb line and great circle in the description of “steering”. I’ve undone them. — Andy Anderson 12:31, 18 December 2017 (UTC)