[Roger G]

Sailors have been putting to sea in boats and ships for thousands of years, but it was only in the 14-1500s that really long voyages started to become more common place as trade grew and countries looked to expand their territory. For centuries before that, inspite of some of the great early scientists making observations that suggested the world was spherical, most mariners and probably as a consequence most ordinary people believed the world was flat. It looked flat so why would they be interested in thinking anything else? They were more interested in finding enough to eat, paying their taxes and avoiding going to hell by obeying the church. Every so often, a ship would fail to return and word would spread that they had fallen off the edge of the world.

As time moved on, some of the work of ancient mathematicians and astronomers started to become useful to mariners and navigators as they were able to start using known positions of stars, the moon the sun and the times that these celestial bodies were predicted to be in certain positions. Using rudimentary instruments, the navigators were able to get a better idea of where they were heading, how far it was and were able to find places noted by other mariners. The navigation was subject to the unpredictability of weather, currents, and the difficulty of taking accurate sightings with primitive equipment, but was enough for those who had some knowledge in the matter to start making rudimentary maps of their expeditions for others to follow.

Another interesting development was that it was discovered pretty early on, when sailors started sailing well offshore, that by putting a lookout 50 ft up the mast, they could site land much earlier than they could from the deck. This led to the 'crows nest' which was the lookout position on all seagoing ships right up to the invention of radar. This was also backed up with placing land based beacons on the highest points of the coast as navigation aids, allowing mariners to see them at far greater distances than if they were at sea level. The revolution over a few hundred years in navigation at sea, was largely responsible for the change in opinion from the earth being flat to being spherical. The physical observations of mariners was backing up the findings of the mathematicians and astronomers.

Of course there were always occasional false readings caused by temperature inversions and weather conditions reflecting images from further away as in a mirage in the desert. But as understanding of these improved together with a steady development of the equipment, navigation equally became more accurate. I would add that as an offshore sailor for many years, I have frequently navigated accurately to distant shores and also observed the difference that height makes to observations at sea.

I seriously doubt that there are any offshore sailors that are flat earth believers, but would be interested to hear the views of FEs on my comments.

Roger

[Tom Bishop]

Navigation is based on patterns that are not exclusive to a Round Earth. Lets start from the top:

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.

Longitude is based on time offsets from GMT. To calculate your longitude, you therefore simply need to work out the time difference between noon at your location and noon at the Prime Meridian. It was not possible to calculate latitude easily until the invention of accurate clocks.

The early navigator simply needs to know the Latitude and the Latitude of Britain to know that he needed to sail Northwards or Southwards until the North Star was at a certain angle in the sky. Once this was satisfied he had knowledge that he needed to travel either Eastwards or Westwards to reach Britain (although it was generally unknown how far Eastwards or Westwards he had to travel until accurate clocks were invented). Both of these can also be satisfied when traveling in a diagonal route.

Major locations were given "Latitude" and "Longitudes" based on this; and the distance between those major locations are estimated based on the assumption that the earth is a globe and it had a certain size. No one actually placed a tape measurer between New York and Paris. The Navigator simply knows that he has to get to a certain Latitude and Longitude point. The distance is estimated.

[Tom Haws]

Navigation is based on patterns that are not exclusive to a Round Earth. Lets start from the top:

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.

Longitude is based on time offsets from GMT. To calculate your longitude, you therefore simply need to work out the time difference between noon at your location and noon at the Prime Meridian. It was not possible to calculate latitude easily until the invention of accurate clocks.

The early navigator simply needs to know his own Latitude and the Latitude of Britain to know that he needed to sail Northwards or Southwards until the North Star was at a certain angle in the sky. Once this was satisfied he had knowledge that he needed to travel either Eastwards or Westwards to reach Britain (although it was generally unknown how far Eastwards or Westwards he had to travel until accurate clocks were invented).

Major locations were given "Latitude" and "Longitudes" based on this; and the distance between those major locations are estimated based on the assumption that the earth is a globe and it had a certain size to which these coordinate points were placed on.. No one actually placed a tape measurer between New York and Paris.

Great summary until the last paragraph. The distance between locations can be predicted using Round Earth geographic coordinate calculations. But the distance between locations is also known because of abundant commerce travel between them. This applies to any two major locations on earth thanks to the existence of missiles and airplanes. The fact that know travel distances and modeled Round Earth distances agree is probably the biggest validation of the Round Earth model.

[Tom Bishop]

Great summary until the last paragraph. The distance between locations can be predicted using Round Earth geographic coordinate calculations. But the distance between locations is also known because of abundant commerce travel between them. This applies to any two major locations on earth thanks to the existence of missiles and airplanes. The fact that know travel distances and modeled Round Earth distances agree is probably the biggest validation of the Round Earth model.

Do some thinking about the challenges you would have measuring your distance traveled on a ship or an airplane.

[JAZZEYENANO]

Great summary until the last paragraph. The distance between locations can be predicted using Round Earth geographic coordinate calculations. But the distance between locations is also known because of abundant commerce travel between them. This applies to any two major locations on earth thanks to the existence of missiles and airplanes. The fact that know travel distances and modeled Round Earth distances agree is probably the biggest validation of the Round Earth model.

Think about how a ship or an airplane would measure its distance traveled.

By keeping track of how fast it is going, several ways of doing that you can even do it with out computers if necessary. Even my small motor boat can tell me how fast i'm going so for large commercial vessels all they would have to do is keep a record of the speed and the time. And boom you would know how far you went.

[JAZZEYENANO]

Navigation is based on patterns that are not exclusive to a Round Earth. Lets start from the top:

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.

Longitude is based on time offsets from GMT. To calculate your longitude, you therefore simply need to work out the time difference between noon at your location and noon at the Prime Meridian. It was not possible to calculate latitude easily until the invention of accurate clocks.

The early navigator simply needs to know his own Latitude and the Latitude of Britain to know that he needed to sail Northwards or Southwards until the North Star was at a certain angle in the sky. Once this was satisfied he had knowledge that he needed to travel either Eastwards or Westwards to reach Britain (although it was generally unknown how far Eastwards or Westwards he had to travel until accurate clocks were invented). Both of these can also be satisfied when traveling in a diagonal route.

Major locations were given "Latitude" and "Longitudes" based on this; and the distance between those major locations are estimated based on the assumption that the earth is a globe and it had a certain size. No one actually placed a tape measurer between New York and Paris. The Navigator simply knows that he has to get to a certain Latitude and Longitude point. The distance is estimated.

You summarized about location, but how do you explain the existence of a "crows nest" like described in the question?

[Tom Bishop]

Great summary until the last paragraph. The distance between locations can be predicted using Round Earth geographic coordinate calculations. But the distance between locations is also known because of abundant commerce travel between them. This applies to any two major locations on earth thanks to the existence of missiles and airplanes. The fact that know travel distances and modeled Round Earth distances agree is probably the biggest validation of the Round Earth model.

Think about how a ship or an airplane would measure its distance traveled.

By keeping track of how fast it is going, several ways of doing that you can even do it with out computers if necessary. Even my small motor boat can tell me how fast i'm going so for large commercial vessels all they would have to do is keep a record of the speed and the time. And boom you would know how far you went.

Both the ocean and the air are fluids moving within fluids. You really just know how fast the water is moving past you locally. How do you know how fast you are actually moving?

Navigation is based on patterns that are not exclusive to a Round Earth. Lets start from the top:

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.

Longitude is based on time offsets from GMT. To calculate your longitude, you therefore simply need to work out the time difference between noon at your location and noon at the Prime Meridian. It was not possible to calculate latitude easily until the invention of accurate clocks.

The early navigator simply needs to know his own Latitude and the Latitude of Britain to know that he needed to sail Northwards or Southwards until the North Star was at a certain angle in the sky. Once this was satisfied he had knowledge that he needed to travel either Eastwards or Westwards to reach Britain (although it was generally unknown how far Eastwards or Westwards he had to travel until accurate clocks were invented). Both of these can also be satisfied when traveling in a diagonal route.

Major locations were given "Latitude" and "Longitudes" based on this; and the distance between those major locations are estimated based on the assumption that the earth is a globe and it had a certain size. No one actually placed a tape measurer between New York and Paris. The Navigator simply knows that he has to get to a certain Latitude and Longitude point. The distance is estimated.

You summarized about location, but how do you explain the existence of a "crows nest" like described in the question?

When you increase your altitude you are broadening your perspective lines and have pushed your vanishing point further into the distance.

[Tom Haws]

Do some thinking about the challenges you would have measuring your distance traveled on a ship or an airplane.

To be honest, I thought about those challenges before mentioning it. Those challenges are considered far more carefully by commercial airline schedulers than they ever will be by you and me. We both know that over the course of millions of flights, the commercial airline industry has honed their skills to the tolerance demanded by the economy. We don't have to wave away the challenges personally to know they have been overcome long ago. There are multiple planes flying in various directions in every region at all times. This has been solved. The distances are very well known.

[Tom Bishop]

Do some thinking about the challenges you would have measuring your distance traveled on a ship or an airplane.

To be honest, I thought about those challenges before mentioning it. Those challenges are considered far more carefully by commercial airline schedulers than they ever will be by you and me. We both know that over the course of millions of flights, the commercial airline industry has honed their skills to the tolerance demanded by the economy. We don't have to wave away the challenges personally to know they have been overcome long ago. There are multiple planes flying in various directions in every region at all times. This has been solved. The distances are very well known.

There is no such thing as a reliable airspeed indicator for navigation. A plane is navigating through fluids traveling within fluids and a measurement of the amount of air passing by the craft is meaningless in navigation. Airspeed indicators are only used for telling how much air is passing over the wing locally, for when making banking maneuvers and such.

So again, how do planes know how far they have traveled if there is no such thing as an odometer for airplanes?

The only way is to calculate it based on your Latitude and Longitude and the assumption that the earth is a globe.

[Tom Haws]

You really just know how fast the water is moving past you locally.

This is just not true.

1. You can measure the ground or water passing below with optical sensors or radar.
2. You know your travel time, your engine performance, and your fuel usage repeated thousands of time in different directions.
3. Meteorologists and oceanologists are not ignorant of air and water currents. These have to be factored in to be economically competitive.

[Tom Haws]

how do planes know how far they have traveled if there is no such thing as an odometer for airplanes?

See my answer above. These are not rough surmisings. This is a robust and mature business industry that lives by the numbers. We are not getting free miles for some routes and paying mysteriously high for others. It's all known.

[JAZZEYENANO]

how do planes know how far they have traveled if there is no such thing as an odometer for airplanes?
[/quote/]

When you are near land you can get speed by looking directly at it and measuring your position against it at set times. When farther from land, out of site, radar (if you don't trust radar than well...) but with radar you can check your relative position to land and calculate your speed

[Tom Haws]

Tom Bishop, you are making a big deal out of uncertainties that are not a big deal. They are very small, and they have been abundantly boxed and controlled for over the course of millions of repetitions. We are not ignoring them. But they are not significant to the question.

Don't forget the question about the crow's nest. There must be an answer to that somewhere in the literature.

[JAZZEYENANO]

Tom Haws, I think he said something about perspective lines being pushed back the higher you go. I am not really sure if I completely understand it though.

[Tom Bishop]

You really just know how fast the water is moving past you locally.

This is just not true.

1. You can measure the ground or water passing below with optical sensors or radar.
2. You know your travel time, your engine performance, and your fuel usage repeated thousands of time in different directions.
3. Meteorologists and oceanologists are not ignorant of air and water currents. These have to be factored in to be economically competitive.

1. These commercial planes aren't navigating by radar. Who has measured the distance between two distant points with radar and found it to match the distances predicted by RET lat/lon coordinates?

2. A travel time is meaningless unless you know how fast you were going. Repeating the journey doesn't tell you how fast you were going. To know your average engine performance would require knowledge of how fast your craft is truly traveling, and this is influenced by currents and any Round Earth lat/lon coordinate system misinformation you compare it to (ie. GPS).

3. Even if a pilot knows that he is flying against 5 knot headwinds, there is no way to know how much it is fluctuating as to get an accurate speed estimate.

how do planes know how far they have traveled if there is no such thing as an odometer for airplanes?

See my answer above. These are not rough surmisings. This is a robust and mature business industry that lives by the numbers. We are not getting free miles for some routes and paying mysteriously high for others. It's all known.

It is not so uncommon for an international flight to arrive an hour early, and it is not so uncommon for a flight to arrive an hour late. We know about how long a flight "usually" takes, but we don't really know how fast it was traveling or the distance it traveled.

Here are some random quotes from airliners.net:

LHR-ORD - my BA flight departed ten minutes late and arrived 1 hour early. We went straight to a parking position, and about 30-45 minutes later I was on the subway.

I was flying IAD-LHR on UA back in October. We got in almost an hour early. Normally I wouldn't have minded but I was travelling in F and would have like to have had the extra hours sleep!!

I once flew COSAN-EWR on a red-eye flight that made it from lift-off to touch-down in four hours, fifteen minutes. We had been informed that it might be a bumpy, but we would hit some incredible tail winds.

9:30 PM to 5:30 AM...we arrived at 4:45 AM, a full 45 minutes ahead of schedule.

CGK - (SIN) - AMS

About an hour ahead of schedule.
We even had to wait for the gateway controller (sorry, forgot the actual name of the profession) to come and hook us up.

[JAZZEYENANO]

quoting Tom Bishop
This is just not true.

1. You can measure the ground or water passing below with optical sensors or radar.
2. You know your travel time, your engine performance, and your fuel usage repeated thousands of time in different directions.
3. Meteorologists and oceanologists are not ignorant of air and water currents. These have to be factored in to be economically competitive.
[/quote]

1. These commercial planes aren't navigating by radar. Who has measured the distance between two distant points with radar and found it to match the distances predicted by RET lat/lon coordinates?

2. A travel time is meaningless unless you know how fast you were going. Repeating the journey doesn't tell you how fast you were going. To know your average engine performance would require knowledge of how fast your craft is truly traveling, and this is influenced by currents and any Round Earth lat/lon coordinate system misinformation you compare it to (ie. GPS).

3. Even if a pilot knows that he is flying against 5 knot headwinds, there is no way to know how much it is fluctuating as to get an accurate speed estimate.
[/quote]

Well when you put it like that everything is a lie. If we can't agree on at least one constant this conversation will never go anywhere.

[StinkyOne]

Do some thinking about the challenges you would have measuring your distance traveled on a ship or an airplane.

To be honest, I thought about those challenges before mentioning it. Those challenges are considered far more carefully by commercial airline schedulers than they ever will be by you and me. We both know that over the course of millions of flights, the commercial airline industry has honed their skills to the tolerance demanded by the economy. We don't have to wave away the challenges personally to know they have been overcome long ago. There are multiple planes flying in various directions in every region at all times. This has been solved. The distances are very well known.

There is no such thing as a reliable airspeed indicator for navigation. A plane is navigating through fluids traveling within fluids and a measurement of the amount of air passing by the craft is meaningless in navigation. Airspeed indicators are only used for telling how much air is passing over the wing locally, for when making banking maneuvers and such.

So again, how do planes know how far they have traveled if there is no such thing as an odometer for airplanes?

The only way is to calculate it based on your Latitude and Longitude and the assumption that the earth is a globe.

You know Tom, we might give your position more consideration if planes were arriving late, getting lost, stalling from flying to slow, being damaged by flying too fast, running out of fuel mid-flight, etc. It is the height of arrogance to think that you have more information/knowledge on air travel than the entire aviation community. You should stick to arguing things that no one can prove, like imaginary perspective lines.

Fluids in fluids - if you know the speed of the head or tail wind, altitude, and indicated airspeed, you can calculate a reasonable ground speed with nothing more than simple arithmetic. (GPS and radar are much better, but it can be done) Engine flow rate produce known levels of power and thus known air speeds at different altitudes. (thrust/drag ratio) There is literally nothing left to chance in aviation. It is a life or death business and losing a single plane can be disastrous for an airline.

GPS and other guidance technologies have gotten so good that newer planes can land themselves if need be. A pilot in New York can program his autopilot to fly to LA and land on a 200' wide strip of concrete. Navigation and GPS work because the Earth is a globe.

[douglips]

It was not possible to calculate latitude easily until the invention of accurate clocks.

I think you mean longitude here.

I don't know why we're so focused on measuring distances over water and air when we can just measure distances over land.

You can go from Tierra del Fuego to Barrow, Alaska on a continuous highway. It turns out that 1 degree of latitude = 60 nautical miles, always.

You can go from Paris to Vladivostok by rail, and it turns out that the distance per degree longitude is a well worn, well tested formula. A degree of longitude is 60 nautical miles at the equator, and it is corrected by the cosine of latitude.

This doesn't by itself condemn flat earth, but it makes flat earth models very difficult to create and match up with these observations. One possible explanation for that is that the earth is not flat.

[Tom Haws]

It is not so uncommon for an international flight to arrive an hour early, and it is not so uncommon for a flight to arrive an hour late. We know about how long a flight "usually" takes

1. The statistical standard error (standard deviation/sqrt(nObservations)) of the thousands or millions of repeated flights is very small.

, but we don't really know how fast it was traveling or the distance it traveled.

2. As douglips said right above, this is not as elusive as you make it out to be.
A. A flight from LA to London is mostly overland. And the distance from LA to Thunder Bay, Ontario is known by road distances and surveyed rights-of-way. Calibration with land legs is not difficult. The oceans are not a mysterious void where different laws apply.
B. Many remote cities (LA and Buenos Aires, Tangier and Capetown, Shanghai and Lisbon) are connected entirely by land routes.

[Roger G]

Navigation is based on patterns that are not exclusive to a Round Earth. Lets start from the top:

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.

Longitude is based on time offsets from GMT. To calculate your longitude, you therefore simply need to work out the time difference between noon at your location and noon at the Prime Meridian. It was not possible to calculate latitude easily until the invention of accurate clocks.

The early navigator simply needs to know the Latitude and the Latitude of Britain to know that he needed to sail Northwards or Southwards until the North Star was at a certain angle in the sky. Once this was satisfied he had knowledge that he needed to travel either Eastwards or Westwards to reach Britain (although it was generally unknown how far Eastwards or Westwards he had to travel until accurate clocks were invented). Both of these can also be satisfied when traveling in a diagonal route.

Major locations were given "Latitude" and "Longitudes" based on this; and the distance between those major locations are estimated based on the assumption that the earth is a globe and it had a certain size. No one actually placed a tape measurer between New York and Paris. The Navigator simply knows that he has to get to a certain Latitude and Longitude point. The distance is estimated.

I can see that using celestial bodies for navigation could well apply to a flat earth, however to make any sense of those sightings it is necessary to have a map to know where you are in relation to your intended destination. Once basic navigation became established, maps were quickly made to enable others to find the same destinations. However contrary to your answer, even basic navigation at sea is able to give a reasonably accurate estimation of distance travelled. Logs for measuring speed through the water have been trailed behind ships for centuries and before that, as I am sure you are aware, knotted ropes were paid out to assess the speed, hence knots as a nautical measure. By plotting the speed through the water against sighted positions and time run, tracking angles to compensate for the effects of currents and tidal and wind movements can easily be set using basic maths to give a pretty accurate dead reckoning idea of distance travelled and position. Even today if I am sailing offshore, I still use charts and sightings to give a dead reckoning position which I can confirm by gps and or radar. I have also frequently measured distances on a radar scanner and most modern radar equipment would be incorporated with gps positioning and chart plotters to confirm position and keep on course. Distance travelled is automatically shown on the chart plotter screen. Positional accuracy is vital in modern marine navigation and highly accurate charts are vital for ships to be able to accurately and safely plot their passages. On my own boat, I also have AIS incorporated in my chart plotter which picks up gps positional information from other ships and plots them on my screen against my own course and speed and warns me if any hazards present themselves in any area that I mark on my course.

As you freely admit, there are no proven accurate flat earth maps, so none of the above would work in a flat earth scenario where absolute precision is required in a wide range of conditions.

I'm also interested in your nonsensical answer to the Crows Nest question.
'When you increase your altitude you are broadening your perspective lines and have pushed your vanishing point further into the distance'

Can you show evidence of where it has been demonstrated and verified that your perspective and vanishing point hypothesis is not just a load of magic waffle. In my personal many years of flying and sailing I have clearly seen that your explanation is rubbish. I can see about 3 miles from the deck of my boat to a flat horizon and many more if I climb up the mast. All very obvious given the curvature and size of a spherical earth.

Roger