[Tumeni]

Measure is required over several degrees . You can't measure just one degree and deduce anything meaningful .

I refer you back to my previous post.

Norwood measured out the distance from London to York in the 1600s (some 200 miles or so), so according to the textbooks, he measured somewhere around 2.5 degrees of latitude.

Again, I ask - if you accept positioning of places by reference to degrees of latitude or longitude, where are you drawing the angle?

Definition; "an angle is the figure formed by two rays, called the sides of the angle, sharing a common endpoint, called the vertex of the angle".

Where is your endpoint, the vertex of the angle? 

[GreatATuin]

As far as the southern hemisphere goes, I'd rather stick to the north for now as that's a lot simpler to think about with just Polaris to deal with. Apologies to anyone down south.

Anyway, it's not really different, it just takes a little more effort to determine the latitude since there is no bright star at the southern celestial pole.

I suspect that two issues are commonly being lumped together: 1) Does latitude/longitude give you a unique and unchanging position (irrespective of shape)? 2) Are distances calculated between two points expressed as latitude/longitude correct?

When you lump these together, it's not surprising that FEers will dismiss latitude/longitude as globe based, because it's hard to accept 2) without accepting a globe, but I don't see 1) as being anywhere near as contentious. Somerled has given an opinion, but I'm having to read between the lines a bit to figure out exactly where he (gender based assumption there) stands on 1). I'm really hoping we'll hear from a few more FEers, I'm genuinely interested to understand their position(s) on this and reasoning.

Actually, I don't see how 1) could be rebutted. As you said, latitude can be determined with the position of the celestial pole in the sky, and longitude can be determined by calculating the difference between solar noon in Greenwich and local solar noon. Travel west and solar noon will happen later, travel east and it will happen sooner. Travel north and Polaris will appear higher in the sky until you reach the north pole and you see it directly overhead. Travel south and Polaris will appear lower until you reach the Equator and it appears on the horizon, and if you keep on travelling south you can repeat with the southern celestial pole. Latitude and longitude are not just arbitrary values, they have a meaning that can be easily verified by anybody: this fact alone is already a strong argument for a spherical Earth, both latitude and longitude being angular measurements.

Then comes 2). As seen in another thread, values given by online maps are generally accepted as accurate - or at least, no one has proved them wrong. And we've seen they're based on formulas such as haversine or Vincenty's.

Conclusion: we can determine a latitude and longitude of any point on Earth, and we can determine the distance between any two points on Earth knowing their latitude and longitude using a formula that calculates distances on a sphere or an oblate spheroid. It would be a very intriguing coincidence if this worked without the Earth being a globe.

[robinofloxley]

As far as the southern hemisphere goes, I'd rather stick to the north for now as that's a lot simpler to think about with just Polaris to deal with. Apologies to anyone down south.

Anyway, it's not really different, it just takes a little more effort to determine the latitude since there is no bright star at the southern celestial pole.

I suspect that two issues are commonly being lumped together: 1) Does latitude/longitude give you a unique and unchanging position (irrespective of shape)? 2) Are distances calculated between two points expressed as latitude/longitude correct?

When you lump these together, it's not surprising that FEers will dismiss latitude/longitude as globe based, because it's hard to accept 2) without accepting a globe, but I don't see 1) as being anywhere near as contentious. Somerled has given an opinion, but I'm having to read between the lines a bit to figure out exactly where he (gender based assumption there) stands on 1). I'm really hoping we'll hear from a few more FEers, I'm genuinely interested to understand their position(s) on this and reasoning.

Actually, I don't see how 1) could be rebutted. As you said, latitude can be determined with the position of the celestial pole in the sky, and longitude can be determined by calculating the difference between solar noon in Greenwich and local solar noon. Travel west and solar noon will happen later, travel east and it will happen sooner. Travel north and Polaris will appear higher in the sky until you reach the north pole and you see it directly overhead. Travel south and Polaris will appear lower until you reach the Equator and it appears on the horizon, and if you keep on travelling south you can repeat with the southern celestial pole. Latitude and longitude are not just arbitrary values, they have a meaning that can be easily verified by anybody: this fact alone is already a strong argument for a spherical Earth, both latitude and longitude being angular measurements.

I agree with most of what you say here, but to determine your latitude you measure the distance from the horizon to Polaris and since we don't (or at least didn't hundreds of years ago) know the distance to Polaris, we can't figure out an absolute distance, so it makes perfect sense to me to measure the angular distance and use that. In fact I can't think of any alternative. That angular measurement could be observed on a flat earth just as well. Similar argument for longitude.

So my argument is that just measuring latitude/longitude and asserting this gives you a unique position you can always find your way back to, isn't (by itself) predicated on a spherical earth model. So I think there is potential for agreement between both sides on this point.

I've frequently seen arguments dismissed out of hand with FErs saying things like "oh you're using latitude/longitude, they're based on an assumption of a globe so your argument is invalid". I was hoping by splitting the whole latitude/longitude question into two points, one independent of model and the other not, that I could find out if FErs could at least agree on 1). Unfortunately, with the exception of somerled, nobody else from that side appears to be interested enough to engage, which is disappointing.

Then comes 2). As seen in another thread, values given by online maps are generally accepted as accurate - or at least, no one has proved them wrong. And we've seen they're based on formulas such as haversine or Vincenty's.

Conclusion: we can determine a latitude and longitude of any point on Earth, and we can determine the distance between any two points on Earth knowing their latitude and longitude using a formula that calculates distances on a sphere or an oblate spheroid. It would be a very intriguing coincidence if this worked without the Earth being a globe.

Yes indeed, but I can't imagine many FErs agreeing that distances calculated using spherical trig are going to be valid. iamcpc went to a lot of effort to avoid the obvious conclusion that Bing maps distances are based on a spherical model.

Ideally I'd like to hear a bunch of FErs say "yes, latitude and longitude work and give you a fixed, unique position. No you can't calculate distances with them because...". At least that would clarify their position.

[somerled]

Just to make my position clear .

I am not taking a FE or RE stance on latitude . A survey of length of successive degrees of latitude along a meridian , with respect to the pole star , will give a clear indication of the shape of the land . It's just geometry . If you don't know the distance to the pole then it can be calculated from those results .

This is the point , the results are determined by measurement not theory. Any coordinate system will give unique values to each point but if want them to conform to the real shape of earth then you have to deduce that shape .

[Tumeni]

I am not taking a FE or RE stance on latitude . A survey of length of successive degrees of latitude along a meridian , with respect to the pole star , will give a clear indication of the shape of the land. It's just geometry . If you don't know the distance to the pole then it can be calculated from those results .

This is the point , the results are determined by measurement not theory. Any coordinate system will give unique values to each point but if want them to conform to the real shape of earth then you have to deduce that shape .

"degrees of latitude along a meridian" has no meaning on FE. As mentioned earlier, where would you draw the angle between the two vectors?

[robinofloxley]

Just to make my position clear .

I am not taking a FE or RE stance on latitude . A survey of length of successive degrees of latitude along a meridian , with respect to the pole star , will give a clear indication of the shape of the land . It's just geometry . If you don't know the distance to the pole then it can be calculated from those results .

This is the point , the results are determined by measurement not theory. Any coordinate system will give unique values to each point but if want them to conform to the real shape of earth then you have to deduce that shape .

No, I get that. I think I understand your position well enough. Without wishing to put words in your mouth, I'd say you were happy enough to accept my proposition 1) - that you can use latitude/longitude in either model to pinpoint an exact position and as for 2) potentially you can determine whether or not you can calculate accurate distance from latitude/longitude, well then, that can be checked/investigated by taking survey measurements along a meridian.

As I said, I was hoping to get a range of opinions from flat earthers on 1) & 2) separately, but not much engagement so far.

[somerled]

"degrees of latitude along a meridian" has no meaning on FE. As mentioned earlier, where would you draw the angle between the two vectors?
[/quote]

A meridian is any straight line from N to S - not hard to understand .

Just to make my position clear .

I am not taking a FE or RE stance on latitude . A survey of length of successive degrees of latitude along a meridian , with respect to the pole star , will give a clear indication of the shape of the land . It's just geometry . If you don't know the distance to the pole then it can be calculated from those results .

This is the point , the results are determined by measurement not theory. Any coordinate system will give unique values to each point but if want them to conform to the real shape of earth then you have to deduce that shape .

No, I get that. I think I understand your position well enough. Without wishing to put words in your mouth, I'd say you were happy enough to accept my proposition 1) - that you can use latitude/longitude in either model to pinpoint an exact position and as for 2) potentially you can determine whether or not you can calculate accurate distance from latitude/longitude, well then, that can be checked/investigated by taking survey measurements along a meridian.

As I said, I was hoping to get a range of opinions from flat earthers on 1) & 2) separately, but not much engagement so far.

For proposition 1 i'd have to say no . What your saying ,it seems to me , is that you can use any coordinate system . Well you can , and it is true that each will give unique results . But there is only one coordinate system which can rightly be called a latitude/longitude coordinate system - the angle of latitude as measured from the pole star . All other coordinate systems are based on math models - not reality . 

Pole star latitude/longitude system cannot fit both FE or RE model . It will fit only one .

You can distort the results of survey by applying a set of calculations which will enable you to map earth as any shape you wish but it won't be reality .

[Tumeni]

"degrees of latitude along a meridian" has no meaning on FE. As mentioned earlier, where would you draw the angle between the two vectors?

A meridian is any straight line from N to S - not hard to understand.

I understand perfectly what a meridian is, but it's the "degrees of latitude" applicable TO the meridian that I'm querying. Where do you draw the angle that's formed by the two vectors connecting the end points of the meridian to the point where the angle of latitude or longitude is defined?

EDIT - where is point C, if the 30 degrees of meridian is defined by the angle between vectors CA and CB?

[somerled]

Point C is the pole star. Where is N - S on your diagram

[Tumeni]

Point C is the pole star. Where is N - S on your diagram

Point C is below the ground.

I thought it was clear that the meridian is line AB, across the surface, and, following convention, the area above that line is sky, and the area below is terra firma.

[robinofloxley]

"degrees of latitude along a meridian" has no meaning on FE. As mentioned earlier, where would you draw the angle between the two vectors?

A meridian is any straight line from N to S - not hard to understand .

Just to make my position clear .

I am not taking a FE or RE stance on latitude . A survey of length of successive degrees of latitude along a meridian , with respect to the pole star , will give a clear indication of the shape of the land . It's just geometry . If you don't know the distance to the pole then it can be calculated from those results .

This is the point , the results are determined by measurement not theory. Any coordinate system will give unique values to each point but if want them to conform to the real shape of earth then you have to deduce that shape .

No, I get that. I think I understand your position well enough. Without wishing to put words in your mouth, I'd say you were happy enough to accept my proposition 1) - that you can use latitude/longitude in either model to pinpoint an exact position and as for 2) potentially you can determine whether or not you can calculate accurate distance from latitude/longitude, well then, that can be checked/investigated by taking survey measurements along a meridian.

As I said, I was hoping to get a range of opinions from flat earthers on 1) & 2) separately, but not much engagement so far.

For proposition 1 i'd have to say no . What your saying ,it seems to me , is that you can use any coordinate system . Well you can , and it is true that each will give unique results . But there is only one coordinate system which can rightly be called a latitude/longitude coordinate system - the angle of latitude as measured from the pole star . All other coordinate systems are based on math models - not reality . 

Pole star latitude/longitude system cannot fit both FE or RE model . It will fit only one .

You can distort the results of survey by applying a set of calculations which will enable you to map earth as any shape you wish but it won't be reality .

OK, sorry, I thought we were on the same page. Seems not to be the case. Let me have another go at explaining. I won't bother with 2), I'll just stick with proposition 1) for now, see if there is some common ground or not.

For proposition 1, this is just about latitude/longitude. That's the only coordinate system I'm talking about. The units are degrees, either expressed as degrees-minutes-seconds (and fractions thereof) or decimal degrees, whichever you like, no preference on my part. Latitude to be measured however you like really. Quite happy with angular distance from horizon to Polaris (or equivalent in the southern hemisphere), measured with a sextant, quadrant, backstaff, or something else, whatever you prefer, so long as the values it gives are sensible. For longitude, I'd suggest time difference between either the sun or a suitable star transiting due south at a fixed meridian (I'd suggest Greenwich, but flexible on that) and same event occurring at the observer's position. Time difference converted to an angle based on the sun moving at 15 degrees per hour or the sidereal day length if using a star transit. But any sensible method to measure longitude acceptable.

I'm not suggesting a coordinate system based on math calculations, just observations, so long as you don't consider converting a time difference to an angle for longitude to be a math calculation in the sense I think you mean it.

If you are happy with the basic idea of latitude and longitude and you want to suggest suitable equipment and/or methodology, I'm pretty confident we can find agreement there.

[somerled]

Latitude is determined by measure of the angle of pole star above the horizontal plane form position of measure , not the horizon . The plane is found by plumbline and level , the angle of elevation by sextant and quadrant .

Use the stars to determine the meridian . Zenith sector, transit scope , survey instruments . You need to see the pole star . It's not visible during daylight which is why I wouldn't use the sun . Every star will cross the meridian at it's zenith . You will then have a meridian along which you will also have observed and measured degrees of latitude given by the pole star - that point above the geographical N point . Call it whatever you want .

These observations will reveal the shape of earth according to these measurements of latitude along that meridian . It's all survey of land and sky .

You can then plot other meridian position using the fact that the sun completes it's 360 degree journey in 24 hrs. Also will be able to check any predictions.

This is all in the North where the pole star is visible . Once that's done we can move south.

[Tumeni]

Latitude is determined by measure of the angle of pole star above the horizontal plane form position of measure , not the horizon . The plane is found by plumbline and level , the angle of elevation by sextant and quadrant.

So where is the angle formed by two vectors? If you say you are at 30 degrees N, where is that angle drawn?

If it's the angle between your horizontal and the pole star, then all you have determined is the elevation of the pole star from your position.

[somerled]

Take a reading at 30N , take a reading from 29N , measure accurately the distance between the points - and carry it on like so .

[Tumeni]

Take a reading at 30N , take a reading from 29N , measure accurately the distance between the points - and carry it on like so .

So what are the two vector lines which form the angle of latitude?

[robinofloxley]

Latitude is determined by measure of the angle of pole star above the horizontal plane form position of measure , not the horizon . The plane is found by plumbline and level , the angle of elevation by sextant and quadrant .

Use the stars to determine the meridian . Zenith sector, transit scope , survey instruments . You need to see the pole star . It's not visible during daylight which is why I wouldn't use the sun . Every star will cross the meridian at it's zenith . You will then have a meridian along which you will also have observed and measured degrees of latitude given by the pole star - that point above the geographical N point . Call it whatever you want .

OK, well that's my proposition 1 then. Quite happy with the equipment and methodology. So really that's all my proposition 1 is about. I believe this is compatible with either flat or globe earth, it's just a set of observations you make, it doesn't by itself tell you what shape the earth is. So my question to anybody who believes in a flat earth is, do any of you have a problem with this and if so, what is it?

I take it you and I at least can now agree that this is an acceptable method / co-ordinate system for describing a position somewhere, anywhere on earth?

[somerled]

Yeah nice , we agree about the equipment and methodology , and you are correct this is indeed compatible with flat or globe earth .
                  I disagree with your next bit. The set of geometric observations you make will tell you , without preconception , which shape is a better fit for a model of earth .

On a perfect sphere with the pole star at immense distance , light rays would be parallel to the axis of the globe and all degrees of latitude should be equal distance apart since they are governed by the curve of the sphere.

On an oblate sphere ,same distant polestar,  degrees of latitude will lengthen to the North.

On a plain degrees of latitude will shorten to the North only if the polestar is relatively close .

God knows about the pearoid.

It's probably impossible to get true accurate readings due to the diffraction /diffusion etc caused by the air but the general shape should be discernable.

[robinofloxley]

Yeah nice , we agree about the equipment and methodology , and you are correct this is indeed compatible with flat or globe earth .
                  I disagree with your next bit. The set of geometric observations you make will tell you , without preconception , which shape is a better fit for a model of earth .

On a perfect sphere with the pole star at immense distance , light rays would be parallel to the axis of the globe and all degrees of latitude should be equal distance apart since they are governed by the curve of the sphere.

On an oblate sphere ,same distant polestar,  degrees of latitude will lengthen to the North.

On a plain degrees of latitude will shorten to the North only if the polestar is relatively close .

God knows about the pearoid.

It's probably impossible to get true accurate readings due to the diffraction /diffusion etc caused by the air but the general shape should be discernable.

What I mean is, you can determine your position and that by itself doesn't force you to accept a particular model. It's only if you start measuring distances between pairs of locations that the realities of the model need to be considered and I think it's this follow on measuring that's the real problem for FE believers, but it's hard to tell because the argument always seems to be along the lines of "can't use latitude/longitude because that's based on a globe". Well I'm just saying that actually, if you limit yourself to determining position, and put aside the tricky topic of distance, then all you are doing is using some pretty basic instruments to make some simple to understand observations.

I completely agree that if you start measuring distances, that will lead you to draw conclusions about the shape of the earth and if you lump the two together (position+distance), then you just get the standard "can't use that, it's based on a globe" response.

[somerled]

I don't get your point . Last line of your OP .

"So is that it? Are latitude/longitude OK by themselves, but the distances are not? What are the actual objections?"

I have put forward the objections . Why should FE accept an ellipsoid model coordinate system as being suitable to describe earth ?

GPS and the globe are not latitude longitude systems of earth ,  yet they are offered up as proof of a globe because by RE . Why do you think that doesn't deserve objection ?

RE is fond of telling us FE distances don't add up on their imaginary model . This is why the distances are important .

Your last sentence makes no sense - can't fathom that out.

[robinofloxley]

I don't get your point . Last line of your OP .

"So is that it? Are latitude/longitude OK by themselves, but the distances are not? What are the actual objections?"

I have put forward the objections . Why should FE accept an ellipsoid model coordinate system as being suitable to describe earth ?

GPS and the globe are not latitude longitude systems of earth ,  yet they are offered up as proof of a globe because by RE . Why do you think that doesn't deserve objection ?

RE is fond of telling us FE distances don't add up on their imaginary model . This is why the distances are important .

Your last sentence makes no sense - can't fathom that out.

Somehow or other I'm just not managing to explain myself very well and I keep trying different ways to say the same thing. All I can do is keep trying I guess. I don't honestly think there's much if any disagreement with each other. Anyway here goes...

Latitude and longitude pre-date GPS by centuries, so by all means discard any arguments based on GPS, not that I'm using any here.

If you were completely lost, but you had a basic set of instruments (and I think we agree what those are), none of which rely on a globe to function (you just point them at things and measure angles or check timings), you could determine your latitude and longitude. If I had the same basic set of instruments, plus a compass, and you could tell me your position, then in theory I could find you. I just need to travel north or south until we're at the same latitude and then east or west until we're at the same longitude and we should meet. Distances don't matter. This process just works whether the earth is a globe or flat - correct?

So from my point of view, for this purpose and this purpose only, nobody can object to latitude/longitude. But they do. Frequently I come across "you can't use latitude/longitude because it's based on a globe". Well how is this based on a globe? Don't go talking about measuring distances, we only have these basic instruments, we have no means to measure any distances.

In order to determine the truth of this, I'm discarding GPS, spherical geometry, everything globe related. Pretend humanity had never even considered the idea that the world was a globe, pretend we've never invented the ruler or tape measure or even the concept of a distance. Is determining your position (latitude/longitude) possible? Well clearly it is. Is it useful? Again, clearly it is. Why then is it constantly rejected in arguments?

I think it's because latitude/longitude have just become forever associated with the globe and that's what's causing the problem for those who don't believe in the globe.

You keep bringing up distances, well you keep objecting to a point I'm just not making. Leave distances out of it and then tell me what's wrong with latitude/longitude.