[douglips]

I tried to ask this once before (https://forum.tfes.org/index.php?topic=7040.0), and it quickly devolved into arguments about whether a particular flat earth map is accurate, or what path the sun follows.

I'd like to respectfully ask round earth theorists to hold their tongue on this thread, because I don't want any arguments about maps - I just want to know about the concept of latitude and longitude and if flat earth theorists accept it or not.

My original question- do you or other flat earth theorists accept the definition of latitude and longitude or not?

For hundreds of years people have observed the following:
- Latitude is the angle from vertical the sun makes at noon on the equinox.
- Latitude is 90 degrees MINUS the angle from vertical the north star makes.
- Longitude is based on time offsets from GMT, and is the east/west angle the sun makes at GMT. I would understand if you can't accept this definition for anywhere that the sun is not visible at noon GMT, but that still would allow us to talk about longitude over about half of the planet.

Further, people have observed that for a given fixed point on earth, latitude and longitude are unchanging.

Here's an article on how to measure latitude and longitude:
http://www.open.edu/openlearn/society/politics-policy-people/geography/diy-measuring-latitude-and-longitude

Here's a book from 1805 showing how to measure latitude and longitude from the sun, moon, and stars.

If you measure the latitude as navigators have done for hundreds of years, or longitude as they have measured for a lower number of hundreds of years, even if it doesn't mean the Earth is round, do you agree that latitude and longitude lines (of whatever shape) exist?

[Tom Bishop]

The Round Earthers of antiquity who came up with the "latitude" devised their latitudes for various cities and locations based on the angle of the North Star in the sky from that particular location.

The sun thing ("Latitude is the angle from vertical the sun makes at noon on the equinox"), while true under the Round Earth hypothesis, has never really been thoroughly tested or used as the primary method of determining latitude. Having to wait until a certain day of the year and at a certain moment of the day to find out what latitude you are at is inconvenient compared to one you can perform on any night, and is not the primary method used.

I believe that we generally accept that navigators and cartographers have used the North Star for latitude readings; it is the sun proofs that are more in question.

[inquisitive]

The Round Earthers of antiquity who came up with the "latitude" devised their latitudes for various cities and locations based on the angle of the North Star in the sky from that particular location.

The sun thing, while true under the Round Earth theory, has never really been thoroughly tested or used as the primary method of determining latitude. Having to wait until a certain day of the year and at a certain time of the day to find out what latitude you are at is inconvenient compared to one you can perform on any night, and is not the primary method used.

The sun thing works, as you know from timeanddate.com.

[douglips]

You are right that it would be inconvenient to wait for a particular day, but that is not what was in use as of 1805.

The book I linked from 1805 includes the following methods for determining latitude, none of which require you to wait for a particular day, although some require you to wait for a particular time, and others require you to wait for some time interval to elapse:

- To find the latitude of a ship at sea, by the observed meridional altitude of a star (problem V)
- To find the latitude of a ship at sea, by the observed meridional altitude of the moon's limb (problem VI)
- To find the latitude of a ship at sea, by several altitudes of the sun observed near noon (problem VII)
- To find the latitude of a ship at sea, by two observed altitudes of the sun, and the interval of time elapsed between the observations. (Problem VIII)

All of these are in the Problems and Examples section near the very end.

So there is no need to wait for a particular day, or to rely on a single star - if the north star is obscured by clouds, any other star for which you know its location in the sky will do. There's no need to wait for night, you can observe the sun multiple times.

In that book there is a long list of place names and their latitudes and longitudes. The Royal Navy navigated to many of these locations using these techniques.

I would say that qualifies as having tested AND used as the primary method of determining latitude, wouldn't you?

[3DGeek]

Because the Earth is not a perfect sphere - there is a confusing problem with latitude when exactness is required.  Wikipedia defines it thus:

* Geodetic latitude: the angle between the normal and the equatorial plane. The standard notation in English publications is φ. This is the definition assumed when the word latitude is used without qualification. The definition must be accompanied with a specification of the ellipsoid.

* Geocentric latitude: the angle between the radius (from centre to the point on the surface) and the equatorial plane.

* Spherical latitude: the angle between the normal to a spherical reference surface and the equatorial plane.

* Astronomical latitude (Φ) is the angle between the equatorial plane and the true vertical at a point on the surface. The true vertical, the direction of a plumb line, is also the direction of the gravity acceleration, the resultant of the gravitational acceleration (mass-based) and the centrifugal acceleration at that latitude.  Astronomic latitude is calculated from angles measured between the zenith and stars whose declination is accurately known.

Geographic latitude must be used with care. Some authors use it as a synonym for geodetic latitude whilst others use it as an alternative to the astronomical latitude. Latitude (unqualified) should normally refer to the geodetic latitude.

There are also rectifying latitudes, authalic latitude, conformal latitude...maybe some others I forgot.

The distinctions are quite subtle and only matter for very precise work.  However, Tom needs to understand that not a single one of those definitions talks about the sun or equinoxes...so he's talking nonsense.  Astronomical latitude is the one you end up using for navigation...although in the modern world, where precision matters, it is necessary to use the WGS-84 spheroid to correct the results to match whatever map you're using.

However, none of these definitions mean anything at all on a Flat Earth map because all of the definitions produce the answer "0 degrees" for every point on the Earth.

It appears from the two FE maps that we've seen that the lines that are drawn on them are an effort to make it possible to compare the known lat/long of (say) a city to the corresponding location on the FE map.

[Tom Bishop]

You are right that it would be inconvenient to wait for a particular day, but that is not what was in use as of 1805.

The book I linked from 1805 includes the following methods for determining latitude, none of which require you to wait for a particular day, although some require you to wait for a particular time, and others require you to wait for some time interval to elapse:

- To find the latitude of a ship at sea, by the observed meridional altitude of a star (problem V)
- To find the latitude of a ship at sea, by the observed meridional altitude of the moon's limb (problem VI)
- To find the latitude of a ship at sea, by several altitudes of the sun observed near noon (problem VII)
- To find the latitude of a ship at sea, by two observed altitudes of the sun, and the interval of time elapsed between the observations. (Problem VIII)

All of these are in the Problems and Examples section near the very end.

So there is no need to wait for a particular day, or to rely on a single star - if the north star is obscured by clouds, any other star for which you know its location in the sky will do. There's no need to wait for night, you can observe the sun multiple times.

In that book there is a long list of place names and their latitudes and longitudes. The Royal Navy navigated to many of these locations using these techniques.

I would say that qualifies as having tested AND used as the primary method of determining latitude, wouldn't you?

Have you read these passages? They take celestial positions and have the navigator jump through a lot of hoops to compute a latitude.

The celestial bodies operate in patterns in the Flat Earth model. The latitude lines upon the earth are also a pattern. It is possible to figure out the output of one pattern by correlating it with another.

Please look at this following passage and tell us how it can only suggest that the earth is round:

[gizmo910]

The celestial bodies operate in patterns in the Flat Earth model. The latitude lines upon the earth are also a pattern. It is possible to figure out the output of one pattern by correlating it with another.

Can you draw that pattern out on a piece of (flat) paper and conclude a flat earth map from that pattern that also lines up with other data like flight paths and such?

[3DGeek]

The celestial bodies operate in patterns in the Flat Earth model. The latitude lines upon the earth are also a pattern. It is possible to figure out the output of one pattern by correlating it with another.

Can you draw that pattern out on a piece of (flat) paper and conclude a flat earth map from that pattern that also lines up with other data like flight paths and such?

No - they can't.  They don't know what the map is like - so they don't know how the moon moves - so you can't figure out where the lines of longitude go - so you don't know what the map is.

Hence my previous thread about using the known position of the sun (from where it's noon) and the circle of locations where the sun is rising or setting.

[douglips]

No, please stop. I don't want to get into if it supports round Earth it not - I just want to know if latitude is accepted by flat Earth theorists. That can be the basis of conversation, but if we start arguing about round Earth we lose that.

[douglips]

Have you read these passages? They take celestial positions and have the navigator jump through a lot of hoops to compute a latitude.

I have. Those hoops you have to jump through are called math, and I'm not in anyway afraid of it.

The celestial bodies operate in patterns in the Flat Earth model. The latitude lines upon the earth are also a pattern. It is possible to figure out the output of one pattern by correlating it with another.

Thank you. That's all that really matters, because if you can observe the patterns and determine that a thing called latitude exists, then we can talk about things like the equator, the tropics, the Arctic circle, and so on.

That's all I want to be able to do.

Please look at this following passage and tell us how it can only suggest that the earth is round:

No. I don't care if it supports round or flat Earth. All I care about is that I can say things like "the sun is directly over the equator at noon on the equinox" and you'll agree with me whole heartedly instead of asking for me to rehash centuries of knowledge.

Thanks!

[3DGeek]

No, please stop. I don't want to get into if it supports round Earth it not - I just want to know if latitude is accepted by flat Earth theorists. That can be the basis of conversation, but if we start arguing about round Earth we lose that.

Then what Tom said:

I believe that we generally accept that navigators and cartographers have used the North Star for latitude readings

...that's your answer.  You measure the perceived elevation of the Pole Star (aka Polaris, aka North Star) above the horizon - and that tells you your latitude.   This has the "Tom-stamp-of-approval".   It's odd that it depends on magic-perspective to work...but that's the definition.

That's a perfectly viable RET definition - so long at the Earth's axis or Polaris itself don't move too much (they do both move a little - but not enough to cause problems).

^{But since I'm not convinced by magic perspective - I think that a real flat earth would have seriously screwed up latitudes.}


However, you first asked about longitude - which is a harder definition than latitude...it would be nice to hear whether Tom has a definition of that.

My guess would be related to the time that the sun reached it's maximum elevation relative to the time in Greenwich, UK.

Trouble is that neither Tom's latitude nor my longitude definition matches the alignment of North and South on either of the two FE maps.