[robinofloxley]

I've read a number of posts where latitude and longitude are dismissed by FErs because they are based on a globe earth.

I'd like to unpick this and ask what the actual objections are.

Fundamentally (if you live in the northern hemisphere), your latitude is easily determined. It's simply the altitude of Polaris from your location. It's not an absolute value in miles, km or light years, because to determine that you'd need to know how far away Polaris is and in times past, that wasn't possible to determine. What we do instead is measure the angle from the horizon to the star, because that's easily done and doesn't require you to know any distances.

Longitude is based on time. When was the sun due south at your location compared to when it was due south in Greenwich UK? If that's +1 hour and the sun moves at 15 degrees per hour, then your longitude is 15W.

Both of these are determined easily from the positions and movements of celestial bodies and can be measured with simple instruments (if you consider an accurate timepiece to be a simple instrument).

Neither of these values rely on any preconceived assumption about the shape of the earth.

There is an issue of course if you want to calculate the distance between two points given by latitude/longitude, because that involves spherical geometry and includes an assumption about the shape of the earth.

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

[somerled]

Good description of how we can measure lat and long in the northern part of the world.

However you state the globe theory preconceived assumption that Polaris is at an extreme distance thus its light rays are basically parallel leading to the conclusion that any change in measured angle of elevation to the star is a product of the curvature of this globe .

FE position .This change of angle to Polaris, as we move N or S , allows calculation by geometric method of the approximate distance to the star and its approximate height above the geographic N pole. No assumptions just scientific observation .

It is possible to determine the approximate shape of the earth through the use of precision scientific instruments , sextants , quadrants , zenith sectors and use of geometric surveying technique.

Survey along a meridian and the shape will reveal itself as distance between successive lines of latitude are measured, as will the approximate distance to the pole star - be it near or far.

Geodesy is the applied mathematical method used to map plane geometric survey results onto a sphere .  In itself it is not a science .

Geometry is is the measure of earth as the name implies .

[AATW]

FE position .This change of angle to Polaris, as we move N or S , allows calculation by geometric method of the approximate distance to the star and its approximate height above the geographic N pole. No assumptions just scientific observation.

Right, but the thing I don't understand about FE is that the observations show that for each degree of latitude the angle to Polaris drops by a degree AND degrees of latitude are equidistant. On a FE if light travels in a straight line then that would not be the case, it's simple geometry:



So is your belief that degrees of latitude are not equidistant? Or is it that light is bending? Or something else?

[somerled]

Degrees of latitude can only be equidistant on a perfect sphere with parallel light rays from an extremely distant North star.

I should imagine that light bends in an electromagnetic field - problematic because we don't know the true nature of light -and there's  atmospheric scattering/diffusion etc.

The coordinate system of gps is based on a math model , not the real shape of earth .

 

[robinofloxley]

Good description of how we can measure lat and long in the northern part of the world.

However you state the globe theory preconceived assumption that Polaris is at an extreme distance thus its light rays are basically parallel leading to the conclusion that any change in measured angle of elevation to the star is a product of the curvature of this globe .

No I've not stated anything about the distance to Polaris (extreme or otherwise), other than simply saying that in times past, the distance was not known, but we can however use an angular measurement instead, which works independently of distance. For instance I can measure the angular height of a tree at the bottom of my garden from my current position. It doesn't tell me anything about the actual height of the tree or how far away it is or for that matter, what shape the earth is.

Equally, it doesn't matter whether the light rays from Polaris are parallel or not, just that whenever you measure the angular elevation of Polaris from the same position, you are always going to get the same value and if you move north or south of that position, you will get a different value, which will increase as you move north and decrease as you move south.

It is possible to determine the approximate shape of the earth through the use of precision scientific instruments , sextants , quadrants , zenith sectors and use of geometric surveying technique.

Survey along a meridian and the shape will reveal itself as distance between successive lines of latitude are measured, as will the approximate distance to the pole star - be it near or far.

Geodesy is the applied mathematical method used to map plane geometric survey results onto a sphere .  In itself it is not a science .

Geometry is is the measure of earth as the name implies .

I agree with all of the above, however that's jumping ahead somewhat for me, as I'm simply at this point trying to get to the bottom of the objections raised regarding latitude and longitude.

[robinofloxley]

Degrees of latitude can only be equidistant on a perfect sphere with parallel light rays from an extremely distant North star.

I should imagine that light bends in an electromagnetic field - problematic because we don't know the true nature of light -and there's  atmospheric scattering/diffusion etc.

The coordinate system of gps is based on a math model , not the real shape of earth .

Again I agree with all of that, but does that mean latitude and longitude can be used to identify a (unique) position and the problems only arise when you then try and use this as a basis for determining distances? For example, I'm quite satisfied that if you were to give me an arbitrary position in terms of latitude/longitude within say 50 miles of my house, then I'd be able to find my way there and send you a photo and you'd agree we were talking about the same place.

[Tumeni]

Degrees of latitude can only be equidistant on a perfect sphere with parallel light rays from an extremely distant North star.

Degrees of latitude have no meaning whatsoever on a flat plane. All you've measured is the angle to polaris. Where would you draw the angle of latitude?

Also, you've skipped completely over people in the South, and how to determine longitude.

EDIT: Let us presume for purposes of this thread that we have an observer on a globe/sphere Earth looking at Polaris;



All vertical lines P lead to Polaris. The observer has a horizontal H, and measures 30 degrees above his horizontal as the elevation to Polaris. Simple geometry shows that if his angle E = 30, then the angle between the two radials to the equator and to his position, angle L, also = 30.

Simple geometry tells us that for a sphere, the length of an arc on the surface is consistently the same, whereever the 30 degrees is measured; 30 degrees down from the pole, 30 degrees up from the equator, the arc will be the same length. Equal division of the circumference into equal parts of one degree, etc.

Thus the distance between points can be calculated and used as a basis for navigation, and thus the nautical mile, a length of arc based on subdivision of a degree of latitude or longitude into equal parts, was born.

Observing angle E tells you what angle L is.

All that would appear to happen with the FE angle to polaris diagram above is that you determine the angle to Polaris. Where is the angle of latitude to be drawn?

[robinofloxley]

Degrees of latitude have no meaning whatsoever on a flat plane. All you've measured is the angle to polaris. Where would you draw the angle of latitude?

Also, you've skipped completely over people in the South, and how to determine longitude.

Here is the problem I'm trying to get to the bottom of. Latitude and longitude are typically dismissed by FEers because they are routinely associated with the despised globe model. I'm trying, for the moment, to unpick that association and ask whether or not you can use latitude and longitude simply to identify a unique location on the earth. From that viewpoint, if we don't care about meaning, does measuring the angle to Polaris on its own - irrespective of model, distance to Polaris, whether or not light travels in straight lines etc. etc. - locate you along a north-south line and when combined with latitude, does that give you a unique location?

I totally get that when you then start talking about distances and whether or not latitude lines are equally spaced, that causes difficulties with the globe vs. flat models. But fundamentally, is there anything wrong (from the FE perspective) with latitude and longitude as an indicator of position?

I'm just not clear what the consensus is (if there is one of course) amongst FEers on this issue.

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.

[somerled]

Sorry Robin , I misread your OP about distance to Polaris .

Measuring distances between degrees of latitude taken from the North star will give systematic difference on FE . Surveying these distances along a meridian will indicate which model is closer to the truth.

That the equator is given as 0 degrees midway between the globe geographic poles is an assumption used to model earth as a globe.

In practice it should be possible to survey the distance closely enough to give a true distance between the geographic N pole and the equator since at the pole you are directly beneath the pole star , and at the equator you are directly beneath the path of the sun at equinox .

If you surveyed a fair distance , say from 70N to 40S if possible then you could extrapolate distance southwards to the equator  - make a prediction then check this with survey. It becomes harder to track the pole star accurately at lower elevations as you travel towards the equator but the predicted position could be checked against the real one .

This is the simple way to determine the shape of earth . Hope this makes sense

The longitude positions used by gps should be the same in both models but latitudes will differ with shape although by how much will be given by survey .

 

[Tumeni]

If you surveyed a fair distance , say from 70N to 40S if possible then you could extrapolate distance southwards to the equator  - make a prediction then check this with survey.

This is the simple way to determine the shape of earth.

...and that's exactly what Norwood did in the 1600s to calculate the circumference.

The French Geodesic Mission repeated the exercise in the 1700s, with a slightly different method, which reinforced Norwood's figure, within reasonable bounds of error for the methods used.

Determining distance from pole to equator is then simple arithmetic. Circ divided by 4.

Since verified by other, progressively more accurate methods.

[robinofloxley]

Sorry Robin , I misread your OP about distance to Polaris .

Measuring distances between degrees of latitude taken from the North star will give systematic difference on FE . Surveying these distances along a meridian will indicate which model is closer to the truth.

That the equator is given as 0 degrees midway between the globe geographic poles is an assumption used to model earth as a globe.

In practice it should be possible to survey the distance closely enough to give a true distance between the geographic N pole and the equator since at the pole you are directly beneath the pole star , and at the equator you are directly beneath the path of the sun at equinox .

If you surveyed a fair distance , say from 70N to 40S if possible then you could extrapolate distance southwards to the equator  - make a prediction then check this with survey. It becomes harder to track the pole star accurately at lower elevations as you travel towards the equator but the predicted position could be checked against the real one .

This is the simple way to determine the shape of earth . Hope this makes sense

The longitude positions used by gps should be the same in both models but latitudes will differ with shape although by how much will be given by survey .

OK, so I hope I've understood your position correctly. You seem happy to accept a position expressed as a latitude/longitude would identify a unique location whatever the shape of the earth and seem OK with the idea of using GPS to obtain a position fix too. That's really what I'm trying to establish, just to see if there is common ground here and it sounds like there is. Any idea whether this is a generally held view within FE? For me, one of the biggest difficulties is understanding where the common ground is in order to have a rational discussion about anything.

I completely agree that if we accept latitude/longitude positions as meaningful and (reasonably) accurate, then measuring a degree or so of either or both would support one model over another. Where we no doubt disagree is that I think these measurements have already been taken and they point to a globe earth.

[somerled]

GPS is a coordinate system based on a math model , a set of calculations used to determine position , not done by measurement or observation . I don't see the need for GPS . Survey will reveal all.

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

[Nosmo]

Robin, this is something I have wondered for a while too. How is Latitude and Longitude a round earth coordinate system as is sometimes claimed here.

As you say if in the northern part of the world you go to a particular place and measure the angle to Polaris it will always be the same, and we call that Latitude and measure it in degrees. If you move North the angle increases and if you move south it decreases.
In the southern part of the world there is a similar spot in the sky that can be used, it is not marked with a convenient star like in the north so it is not as straight forward to make the measurement.
The range of this measure is from 90 degrees North through 0 degrees to 90 degrees South.

As you also say Longitude can be measured in time offset. Again in the northern part of the world how long after the sun is due south from a reference point (Greenwich) is it due south in your location. All you need to measure this is a timepiece set to Greenwich time. This can be measured in hours or minutes for example.

Using these two measures should give a unique and consistent coordinate pair for any location on the Actual Earth.

The only concession to a circular world (either globe or disc) is in the representation of Longitude not in hours or minutes but rather in four minute increments and refereed to as degrees. This is based on the 24 hours for a cycle of the sun to complete one circle above a disc earth or the earth to complete one rotation in the globe earth. Either way 1/360 of 24 hours is 4 minutes.

I think your main question is, do Flat Earthers agree that these two basic observational measures give a location coordinate pair (latitude and longitude) that is unique and unchanging for a given location on the Earth?

Further that given an latitude and longitude for a location it would be possible to navigate to that point using only the measurement techniques described above. You may not know the distance or the direction, but you could travel north or south to get to the correct latitude, and then travel east or west to get to the right longitude. Not the most efficient path, but it would get you there.

[robinofloxley]

Robin, this is something I have wondered for a while too. How is Latitude and Longitude a round earth coordinate system as is sometimes claimed here.

As you say if in the northern part of the world you go to a particular place and measure the angle to Polaris it will always be the same, and we call that Latitude and measure it in degrees. If you move North the angle increases and if you move south it decreases.
In the southern part of the world there is a similar spot in the sky that can be used, it is not marked with a convenient star like in the north so it is not as straight forward to make the measurement.
The range of this measure is from 90 degrees North through 0 degrees to 90 degrees South.

As you also say Longitude can be measured in time offset. Again in the northern part of the world how long after the sun is due south from a reference point (Greenwich) is it due south in your location. All you need to measure this is a timepiece set to Greenwich time. This can be measured in hours or minutes for example.

Using these two measures should give a unique and consistent coordinate pair for any location on the Actual Earth.

The only concession to a circular world (either globe or disc) is in the representation of Longitude not in hours or minutes but rather in four minute increments and refereed to as degrees. This is based on the 24 hours for a cycle of the sun to complete one circle above a disc earth or the earth to complete one rotation in the globe earth. Either way 1/360 of 24 hours is 4 minutes.

I think your main question is, do Flat Earthers agree that these two basic observational measures give a location coordinate pair (latitude and longitude) that is unique and unchanging for a given location on the Earth?

Further that given an latitude and longitude for a location it would be possible to navigate to that point using only the measurement techniques described above. You may not know the distance or the direction, but you could travel north or south to get to the correct latitude, and then travel east or west to get to the right longitude. Not the most efficient path, but it would get you there.

This is exactly right and precisely what I'm trying to get to the bottom of. 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.

[somerled]

About 1. Latitude/longitude gives a unique unchanging position with respect to where you are on earth . The distance between each degree of latitude is dependent on the shape of earth .

That's geometry , not FE or globe theory - a survey along a meridian with respect to the pole star will give the geometric shape whatever that is. That is all that needs to be done .

GPS is not based on a globe earth - it is based on an elipsoid math model we are told. It's not needed for long/lat.

[robinofloxley]

About 1. Latitude/longitude gives a unique unchanging position with respect to where you are on earth . The distance between each degree of latitude is dependent on the shape of earth .

That's geometry , not FE or globe theory - a survey along a meridian with respect to the pole star will give the geometric shape whatever that is. That is all that needs to be done .

Thanks, that's clear enough, I believe I understand your position on this and agree with it entirely.

GPS is not based on a globe earth

Given the rest of what you say, I'm not sure I understand that.

 - it is based on an elipsoid math model we are told.

Agree, but an ellipsoid model of the globe surely?

It's not needed for long/lat.

Agreed, but it can be (amongst other things) used to determine or verify your position in terms of latitude/longitude. For that purpose, I'd say it was accurate enough and a lot quicker and more reliable than the older more traditional methods.

[somerled]

About GPS - a math model based on assumed globe . That's the point . All surveys are geometric . The shape of earth will be revealed by this method. Why would you use GPS.

All geometric survey then is subjected to the method of geodesy i.e. spherical calculation for the purpose of mapping the results onto globe  - it's math modelling again .

GPS could be nothing more than a program designed to remove the spherical calculations to give back the geometric survey results , we could check that after the geometric survey results have determined the shape.

[robinofloxley]

About GPS - a math model based on assumed globe . That's the point . All surveys are geometric . The shape of earth will be revealed by this method. Why would you use GPS.

If you trust that a GPS device would give you an accurate value for your latitude, you might as well use it. If you don't, or you want to avoid criticism, then either don't use a GPS at all or use it to cross check against another method e.g. angle of Polaris. For myself, I would be happy to just use a GPS device. To convince others, I would probably use a GPS and some other method and record both results for comparison. For a small extra effort you're conducting a secondary experiment comparing GPS with whatever other method you are using. Two for the price of one.

All geometric survey then is subjected to the method of geodesy i.e. spherical calculation for the purpose of mapping the results onto globe  - it's math modelling again .

GPS could be nothing more than a program designed to remove the spherical calculations to give back the geometric survey results , we could check that after the geometric survey results have determined the shape.

Makes sense.

[somerled]

Well , hopefully I've outlined a valid objection which I believe is what you required from an FE point of view .

My objection is not really an FE argument but a geometric one. If I had a GPS device I'd happily use it myself .

Once all distances and angles have been measured then we could input all data and have a geometric positioning system - GPS for short

[IronHorse]

So where does the signal that my GPS receiver picks up come from?