# lowest great circle constant altitude flight? **URL:** \ **Category:** Factual Questions\ **Created:** [September 10, 2014, 6:35pm UTC](https://boards.straightdope.com/t/lowest-great-circle-constant-altitude-flight/698100 "2014-09-10T18:35:55Z")\ **Posts on this page:** 10\ **Page:** 2
**Author:** ![jtur88](https://avatars.discourse-cdn.com/v4/letter/j/e9c0ed/32.png) [@jtur88](https://boards.straightdope.com/u/jtur88)\ **Post date:** [September 11, 2014, 4:35pm UTC](https://boards.straightdope.com/t/lowest-great-circle-constant-altitude-flight/698100/21 "2014-09-11T16:35:55Z")
Ninja’d by the draconian 5-minute czar. Pacific Ocean, not Indian, passing through the Bering Straits and the Drake Passage. ---
**Author:** ![Ravenman](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ravenman/32/2929_2.png) [@Ravenman](https://boards.straightdope.com/u/Ravenman)\ **Post date:** [September 11, 2014, 4:42pm UTC](https://boards.straightdope.com/t/lowest-great-circle-constant-altitude-flight/698100/22 "2014-09-11T16:42:34Z")
Hm, I found one route that takes off from roughly London, towards the Bay of Biscay, goes just west of Portugal, over Cape Verde, skirts the east side of Brazil, right over the Falklands, continues down (?) to New Zealand, more or less right over Saipan, west of Tokyo, up over Heilongjiang Province in China, through nowhere-in-particular Siberia, over Scandanavia and back to London-ish. It looks like the highest altitude along that route is roughly 6,000 feet, somewhat in the area of Lake Baikal. ---
**Author:** ![jtur88](https://avatars.discourse-cdn.com/v4/letter/j/e9c0ed/32.png) [@jtur88](https://boards.straightdope.com/u/jtur88)\ **Post date:** [September 11, 2014, 4:50pm UTC](https://boards.straightdope.com/t/lowest-great-circle-constant-altitude-flight/698100/23 "2014-09-11T16:50:31Z")
More or less approximating this line, which is 25,000 miles. NM, Google maps won’t allow my marked route to embed. It went through London, Drake’s Passage off Cape Horn, New Zealand area, and Bering Straits. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [September 11, 2014, 6:13pm UTC](https://boards.straightdope.com/t/lowest-great-circle-constant-altitude-flight/698100/24 "2014-09-11T18:13:26Z")
> [@GusNSpot](#): > > Without even a slight jig or jog? > You have a globe? > You can get to Google Earth? > I’m just as lazy as anybody, so I do not put effort into … well, you get the idea. > [@GusNSpot](#): > > Easy, circle Antarctica. Did not even have to look anything up. > > Oh, your definition of circumnavigate is that it must be cutting the Earth into equal halves, not have a bend in the line? Why did you not say so?? > Why do you get to define ‘circumnavigate’ that way when everybody else who actually do circumnavigation don’t? > > Do I have to use True North or Can I use Magnetic North? > > I’m still not going to go do it for you. **Moderator Note** **GusNSpot** , if you cant’ answer a question in GQ there is really no reason for you to comment on it. This is especially true when it’s clear you didn’t really understand what the OP was asking. Let’s refrain from doing so in the future. Colibri General Questions Moderator ---
**Author:** ![cmosdes](https://avatars.discourse-cdn.com/v4/letter/c/a587f6/32.png) [@cmosdes](https://boards.straightdope.com/u/cmosdes)\ **Post date:** [September 11, 2014, 6:30pm UTC](https://boards.straightdope.com/t/lowest-great-circle-constant-altitude-flight/698100/25 "2014-09-11T18:30:14Z")
> [@jtur88](#): > > The term “great circle” has no applicability to circumnavigation. [Great Circle](http://en.wikipedia.org/wiki/Great_circle) [Circumnavivation](http://en.wikipedia.org/wiki/Circumnavigation) > [@](#): > > A basic definition of a global circumnavigation would be a route which covers at least a great circle, and in particular one which passes through at least one pair of points antipodal to each other. In other words, the shortest route for circumnavigation would be a great circle. While you can circumnavigate the globe under some definitions without following a great circle, the OP specifically specified following a great circle. This, by definition, means no turns at all. It is a straight line along a geodesic path. If I start at A and want to return to A, but I also want to 1. circumnavigate the globe b) follow a great circle path iii) never change my altitude What route should I take? ---
**Author:** ![Desert\_Nomad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/desert_nomad/32/177_2.png) [@Desert\_Nomad](https://boards.straightdope.com/u/Desert_Nomad)\ **Post date:** [September 11, 2014, 6:35pm UTC](https://boards.straightdope.com/t/lowest-great-circle-constant-altitude-flight/698100/26 "2014-09-11T18:35:35Z")
The longest water-only Great Circle is from just near Karachi, Pakistan, south through the Mozambique channel, around the southern points of Africa and South America, then northwest to the Kamchatka peninsula (which has some high mountains). ---
**Author:** ![GusNSpot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gusnspot/32/436_2.png) [@GusNSpot](https://boards.straightdope.com/u/GusNSpot)\ **Post date:** [September 11, 2014, 7:51pm UTC](https://boards.straightdope.com/t/lowest-great-circle-constant-altitude-flight/698100/27 "2014-09-11T19:51:25Z")
> [@Colibri](#): > > **Moderator Note** > > **GusNSpot** , if you cant’ answer a question in GQ there is really no reason for you to comment on it. This is especially true when it’s clear you didn’t really understand what the OP was asking. Let’s refrain from doing so in the future. > > Colibri > General Questions Moderator Cool, sorry… ---
**Author:** ![jtur88](https://avatars.discourse-cdn.com/v4/letter/j/e9c0ed/32.png) [@jtur88](https://boards.straightdope.com/u/jtur88)\ **Post date:** [September 11, 2014, 9:53pm UTC](https://boards.straightdope.com/t/lowest-great-circle-constant-altitude-flight/698100/28 "2014-09-11T21:53:05Z")
> [@cmosdes](#): > > [Great Circle](http://en.wikipedia.org/wiki/Great_circle) > > [Circumnavivation](http://en.wikipedia.org/wiki/Circumnavigation) > > In other words, the shortest route for circumnavigation would be a great circle. While you can circumnavigate the globe under some definitions without following a great circle, the OP specifically specified following a great circle. This, by definition, means no turns at all. It is a straight line along a geodesic path. > > If I start at A and want to return to A, but I also want to > > 1. circumnavigate the globe > b) follow a great circle path > iii) never change my altitude > > What route should I take? The critical point in the definition is the antipodes, which would be the points A and B, and the Great Circle, as I said, comes into play only with reference to the route from A to B. The answer to your final question is “through B, the antipodes of A”. Once you locate that point, the great circle defines your two routes – A to B and back to A… ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [September 12, 2014, 1:53am UTC](https://boards.straightdope.com/t/lowest-great-circle-constant-altitude-flight/698100/29 "2014-09-12T01:53:27Z")
> [@](#): > > Quoth **jtur88** : > > I am assuming the OP is looking for a great circle that is defined as equal in length to the circumference of the earth. The question is meaningless if it allows for any smaller circumference. The term “great circle” is what is throwing us off, because that has a specific meaning in navigation that is not applicable here. The question should have been “Is there an undeviating line equal to the circumference of the earth that never passes through a point of relief above 1,000 feet above sea level?” Expressed as a hand-held model, is there a closed loop of string that fits tight over a globe such that it never passes over land of greater than 1,000 feet elevation. How is the term “great circle” throwing anyone off? That’s exactly what it means. A great circle is an undeviating line equal to the circumference of the Earth. ---
**Author:** ![Antonius\_Block](https://avatars.discourse-cdn.com/v4/letter/a/51bf81/32.png) [@Antonius\_Block](https://boards.straightdope.com/u/Antonius_Block)\ **Post date:** [September 12, 2014, 2:22am UTC](https://boards.straightdope.com/t/lowest-great-circle-constant-altitude-flight/698100/30 "2014-09-12T02:22:18Z")
> [@Chronos](#): > > How is the term “great circle” throwing anyone off? That’s exactly what it means. A great circle is an undeviating line equal to the circumference of the Earth. I think that many respondents are conflating the clearly-defined “[great circle](http://en.wikipedia.org/wiki/Great_circle)” with the navigational terms “great circle route” and “great circle path”. Airplanes generally follow great circle routes between origin and destination but never follow the entire great circle in regular service, since that would land them back at their origin. I, too, thought that the OP’s scenario was quite clear, but perhaps the use of “great circle route” in the first paragraph – even though the thread title had the less-ambiguous “great circle” – threw people off. Even so, the combination of “great circle route” and “circumnavigate”, already established by post #3, ought to have cleared matters up. [Previous page](https://boards.straightdope.com/t/lowest-great-circle-constant-altitude-flight/698100.md?page=1)