Offline edby

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Re: One degree of longitude
« Reply #20 on: December 13, 2018, 09:59:21 AM »
And here is a road sign just outside Groblershoop, showing the distance as 285km. So Google maps agrees with road signs.


« Last Edit: December 13, 2018, 10:12:07 AM by edby »

Re: One degree of longitude
« Reply #21 on: December 13, 2018, 01:47:03 PM »
Longitude and Latitude isn't used by Google Maps/WebMercator to measure distances.

Have a read: The Earth is Not Round! Utah, NAD83 and WebMercator Projections

Quote
Latitude and Longitude are useless for measuring distance and area because the unit of length, degrees, is not held constant for longitude, except along parallels -- individual perfectly east-west lines.

...

Web Mercator's significant weakness is that measurements of distance and area in its native coordinates are completely unusable. Where accurate distance and area calculations are needed, web-mercator GIS data must be temporarily reprojected to a more suitable coordinate system (UTM NAD83).

It is admitted that the latitude and longitude coordinates of the spherical earth model is completely unusable, and that the data must be reprojected onto a local state plane coordinate system for accuracy.

You are trying to compare lat/long coordinates which are said to be "completely unusable."

OK Tom, the article you reference specifies UTM NAD83 zone 12 North, so just for you, here is a UTM NAD83 zone 12 North projection of the Falklands/Malvinas with a helpful scale and Hill Cove and Port San Carlos marked. The graticule lines are at 1 deg intervals so it's pretty easy to see how wide a degree of longitude is here I think.

« Last Edit: December 13, 2018, 01:49:58 PM by robinofloxley »

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Offline markjo

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Re: One degree of longitude
« Reply #22 on: December 13, 2018, 02:25:36 PM »
Longitude and Latitude isn't used by Google Maps/WebMercator to measure distances.
Irrelevant.  Latitude and longitude coordinates can be, and often are, used as reference points for navigation and distances between those reference points can be accurately measured and/or calculated.
« Last Edit: December 13, 2018, 02:33:46 PM by markjo »
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Offline edby

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Re: One degree of longitude
« Reply #23 on: December 13, 2018, 02:33:46 PM »
Thank you Mr Hood but lest Tom object that these distances are the result of a conspiracy, below is a road sign from New Zealand, taken just outside Gore where Route 1 crosses the Waikaka River. It says 68km to Balclutha, via a winding route. The crow flies distance according to Google is 59km. Both distances give a longitude 1-degree length of well below 111km.

Where was Rowbotham getting his distances from??



Offline edby

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Re: One degree of longitude
« Reply #24 on: December 13, 2018, 02:48:04 PM »
Rowbotham https://www.sacred-texts.com/earth/za/za42.htm
Quote
If, now, we take, from the same map, the distance between Melbourne and Bluff Harbour, South New Zealand--1400 nautical, or 1633 statute miles--and take the difference of longitude between the two places, allowing 50 statute miles for the angular or diagonal direction of the route to Bluff Harbour, we find the degrees of longitude fully 70 statute miles; whereas, at the average latitude of the two places, viz., 42° S., the degrees, if the earth is a globe, would be less than 54 statute miles; thus showing that in the south, where the length of a degree of longitude should be 54 miles, it is really 70 miles, or 16 miles longer than would be possible according to the theory of the earth's rotundity.

Google says the distance is actually 1331 miles, but let's allow Rowbotham his estimate. He is right that the theoretical GE distance of 1 degree is about 54 miles, and roughly right about the average latitude. However, he is comparing positions with completely different latitudes:

Bluff Harbour -46.60
Melbourne       -37.88

This make the imputed distance longer than if between points with the same difference of longitude but on the same parallel.

[EDIT]
And let's check this with two cities that are nearly on a parallel. See the table below. Adelaide and Sydney are almost on the same latitude. The theoretical length of 1 degree of longitude (using the standard formula, same as Rowbotham was clearly using) is 92.34km.

The difference in longitude is 12.6 degrees, and the Google crow flies distance is 1,163.26 km. Dividing this by 12.6 gives 92.32 km per 1 degree, which is very close to the theoretical number of 92.34 km above.

Adelaide   -34.94   138.60
Sydney   -33.86   151.20
Degee of lat   92.34   12.60
Crow flies   1,163.26   92.32

It is interesting that Rowbotham was clearly aware of the standard cosine formula for determining length of longitude, so he had some mathematical understanding of trigonometry. But not enough to realise that a large difference in latitude would completely distort this result.

Was this an innocent mistake?
« Last Edit: December 13, 2018, 02:57:55 PM by edby »

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Offline RonJ

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Re: One degree of longitude
« Reply #25 on: December 13, 2018, 07:49:56 PM »
Rowbotham actually goes a ways toward proving that the earth is a sphere.  That proof is by his own numbers and calculations. 

His first example in his book was to calculate the distance between Sydney and Nelson.  By his own quote “the two places are nearly on the same latitude”.  Rowbotham’s stated distance between the two ports was 1550 statue miles.  These statements are the crux of the whole problem and seems to be his basis for determining that the earth is NOT as sphere, but flat.  Now lets examine the statements for some discrepancies and apply proven and known modern day math to the statements. 
1st……..Sidney is at 34deg, 00’, 00’’ South by 151deg 11’, 00’’ East
2nd…….Nelson is at 41deg, 16’, 00’’ South by  173deg ,17’,00’ East

The difference in longitude is correct and I agree with that.  However, the difference in latitude is about 7 degrees.  It is true that Rowbotham did say that the differences are ‘nearly’ the same.  Now let’s apply “the whole matter now becomes a mere arithmetical question” quote from Rowbotham and calculate the distance 7 degrees of latitude makes.  That distance going straight North or South is 483 statue miles.  I agree that the route isn’t directly North or South so the whole 483 mile mistake won’t apply.  A modern day measurement between the two ports would yield a distance of about 1305 statue miles.  The difference between Rowbotham’s assumed distance and the corrected one is about 245 miles.

Split the difference between the two latitudes and do a calculation of the points 37.5deg S by 115deg, 11’E  to 37.5deg S by 173deg, 17’E and that comes out to 1208.57 statue miles or 1050.21 Nautical miles.  That’s about 47.7 Nautical Miles per degree longitude at the 37.5 degree South Latitude.  According to Rowbotham’s own chart provided so the reader could make calculations for himself I come up with pretty good agreement with a spherical earth. 

Now I agree that the calculations are a bit tricky.  I didn’t use Google Earth for any distances but effectively did a dot multiplication of two vectors and got the distance between the two coordinates using standard spherical trigonometric methods that would work on any sphere.  These methods are used each and every day by both the shipping companies and airlines so you know for sure that they are quite valid. 

My only assumptions were of the exact locations alluded to by Rowbotham.  I took an estimate and did the calculations with those figures.  If someone wants to provide the ‘official’ Rowbotham approved port coordinates I can re-calculate.

Having said everything above it is hard to determine if the minor calculation error above was intentional to make a case for a flat earth or just a wrong assumption.  The question now is can you trust anything  in Rowbotham’s book and his assumptions that the earth is flat based upon a mistaken assumption? 
You can lead flat earthers to the curve but you can't make them think!

BillO

Re: One degree of longitude
« Reply #26 on: December 13, 2018, 11:24:47 PM »
How can spherical coordinates projected onto a planar coordinate system display data and distances accurately if the earth is a globe? Why should these systems require that? Maps with spherical coordinates are not possible?

This is the first time I've seen you demonstrate the beginnings a modicum of reasoned thinking.  Questions like these are the beginnings of knowledge.  You're lucky in that others have already answered these questions a long time a go.  You can, if you wish, just look up what's already been done, or re-do it if you doubt the veracity of those that came before you.   However. that said, I believe your thinking may have gone off the rails several times just in this thread.

1) What they were saying over at gis.utah.org was not that the world is flat.  It's that we use flat maps.  It was a simple play on words and the technology used for convenience - trust you to take it the wrong way.  But of course, if being obviously worng will support your position, by all means, don't let intellectual honesty stand in your way.

2) When they said lat. and long. were useless for calculating distances they meant when reading those from a map projection, and they meant long distances.  I think you know that too, so don't go on playing the fool.

3) Lat. and long. are perfectly fine for measuring distances on a sphere.  They have to be and if you had any mathematics knowledge at all you would know that.  Of course, as a flat earther your use of spherical coordinates is probably minimal, but that's you fault, not the rest of the world's.  You are free to learn this stuff you know, or are mathematicians considered in on the conspiracy too?

4) To your question "Maps with spherical coordinates are not possible?", not impossible but certainly impractical.  You can get a flat projection map that gives a 10,000:1 magnification, but to accurately do that with spherical coordinates you'd need a globe about 1.3km in diameter.  I'd hate to carry that thing around with me, if I could afford one.

5) BTW, the earth is only non-spherical by a small amount - about 1 part in 300, and this non-sphericality is very regular in nature so can easily be accounted for to get exact results using lat and long on our oblate little earth.  The last official update to the earth's shape measurements was done in 1984 when the actual geodetic of the earth was measured (using some those non-existent satellites) to 12 digits of accuracy.  Applying those corrections lat and long are good for precision in the mm range when applied to the earth's surface.

However, even without those corrections lat and long allowed people to navigate the earth for centuries with amazing and very practical success.  How did they accomplish that supposing a flat earth?  There must be an explanation, as they did actually do it.  Or were James Cook, Ferdinand Magellan and Mr. Polo all shills on the NASA payroll?  How they navigated is all a matter of history and you can read up about it.  Their methods would not work on a flat earth - can you explain for us pleas?  After all, in this thread here you are passing yourself off as a mapping expert.  So expert as to debunk all of modern cartography.

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Offline RonJ

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Re: One degree of longitude
« Reply #27 on: December 14, 2018, 06:38:27 AM »
Rowbotham makes another minor error in calculations as outlined below.

The second example in his book was a route between Melbourne, AU and Bluff Harbor, NZ.  I used the position for Melbourne as 37.8455 South --  144.9425 East and the position for Bluff Harbor as 46.59833 South – 168.345 East.  Using standard spherical trigonometry, I calculated the distance between the two ports at 1160 Nautical Miles.  Due to the fact that there was a southerly component to the route of 8.75 degrees it makes sense that there would be about a 526 nautical miles ‘southing’ on the voyage and the 23.4 degree ‘easting’ would be 962 nautical miles.  Rowbotham did say that he was allowing 50 statute miles for the angular or diagonal direction of the route.  Probably he meant to say 500 Nautical Miles and just made a mistake.  If you divide 962 NM by the 23.4 degree change in Longitude that comes out to a little over 41 nautical miles per degree longitude at 46 degrees South.  The chart in the book would confirm that the expected distance between a degree of Longitude in the spherical earth model is quite close to the calculated distance of 41 nautical miles.

Rowbotham also said that the ‘latitude of Sydney would be 49.74 nautical miles or 58 statute miles’.  If you do the calculation you find the figures above yield a 1.1666 conversion factor to convert Nautical Miles to Statute Miles.  The modern-day figure currently is 1.15078. That’s just another small discrepancy that I noticed.

I’m sure that it was quite difficult for Rowbotham to bring together all the data that he did and attempt the calculations with his limited education.  He didn’t have the nice computers and calculators that are available today.  If you make the minor error corrections and redo all the calculations, you find that the spherical earth paradigm is nicely confirmed by Rowbotham’s data.  Thank You Samuel Rowbotham. 
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Offline Spingo

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Re: One degree of longitude
« Reply #28 on: December 14, 2018, 09:07:44 AM »
Longitude and Latitude isn't used by Google Maps/WebMercator to measure distances.

Have a read: The Earth is Not Round! Utah, NAD83 and WebMercator Projections

Quote
Latitude and Longitude are useless for measuring distance and area because the unit of length, degrees, is not held constant for longitude, except along parallels -- individual perfectly east-west lines.

...

Web Mercator's significant weakness is that measurements of distance and area in its native coordinates are completely unusable. Where accurate distance and area calculations are needed, web-mercator GIS data must be temporarily reprojected to a more suitable coordinate system (UTM NAD83).

It is admitted that the latitude and longitude coordinates of the spherical earth model is completely unusable, and that the data must be reprojected onto a local state plane coordinate system for accuracy.

You are trying to compare lat/long coordinates which are said to be "completely unusable."

Indeed mapping a spherical surface on to flat paper is a tricky prospect with plenty of room to introduce errors. Interesting web site. How do you feel Tom that the link you provided is basing all its prime data on the earth being a sphere? If you accept all the information on this web site it follows you will have to ditch Rowbotham and all your flat earth beliefs.
Thanks for the link as it reinforces how ludicrous the idea of a flat earth map is. One true data set equals the possibility of onetrue map.

Re: One degree of longitude
« Reply #29 on: December 14, 2018, 10:11:00 AM »
Longitude and Latitude isn't used by Google Maps/WebMercator to measure distances.

Have a read: The Earth is Not Round! Utah, NAD83 and WebMercator Projections

Quote
Latitude and Longitude are useless for measuring distance and area because the unit of length, degrees, is not held constant for longitude, except along parallels -- individual perfectly east-west lines.

...

Web Mercator's significant weakness is that measurements of distance and area in its native coordinates are completely unusable. Where accurate distance and area calculations are needed, web-mercator GIS data must be temporarily reprojected to a more suitable coordinate system (UTM NAD83).

It is admitted that the latitude and longitude coordinates of the spherical earth model is completely unusable, and that the data must be reprojected onto a local state plane coordinate system for accuracy.

You are trying to compare lat/long coordinates which are said to be "completely unusable."

Indeed mapping a spherical surface on to flat paper is a tricky prospect with plenty of room to introduce errors. Interesting web site. How do you feel Tom that the link you provided is basing all its prime data on the earth being a sphere? If you accept all the information on this web site it follows you will have to ditch Rowbotham and all your flat earth beliefs.
Thanks for the link as it reinforces how ludicrous the idea of a flat earth map is. One true data set equals the possibility of onetrue map.

Based on the article he quotes, Tom seems to be willing to trust a map generated from a UTM NAD83 projection, but he can't have it both ways. Earlier on I posted a map of the Falklands which is also generated via a UTM NAD83 (Zone 12N) projection (exactly the same one used in the article), so it should by Tom's reasoning be acceptably accurate. The problem is it shows a degree of longitude to be less than 70km wide, which means it's shorter than a degree of longitude on the equator, which means Rowbotham, by his own statements, faced with that evidence, would have had to admit that the earth was "globular" as he put it.

Whether Tom accepts or understands that a UTM NAD83 projection is entirely based on a globe earth or whether he does not, if he trusts that a map produced via this projection is accurate, then OK, here's just such a map and it shows the earth is at the very least "globular".

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Offline AATW

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Re: One degree of longitude
« Reply #30 on: December 14, 2018, 08:59:15 PM »
Whether Tom accepts or understands that a UTM NAD83 projection is entirely based on a globe earth or whether he does not, if he trusts that a map produced via this projection is accurate, then OK, here's just such a map and it shows the earth is at the very least "globular".
A couple of times Tom has posted sources mentioning maps being a projection.
He seems to accept this but I’ve asked him why any projection necessary were the earth flat.
Maps on paper are obviously flat because pieces of paper are flat. Were the earth flat then it would be possible to represent the earth accurately on a map. Projection is necessary only because the earth is not flat.
Tom: "Claiming incredulity is a pretty bad argument. Calling it "insane" or "ridiculous" is not a good argument at all."

TFES Wiki Occam's Razor page, by Tom: "What's the simplest explanation; that NASA has successfully designed and invented never before seen rocket technologies from scratch which can accelerate 100 tons of matter to an escape velocity of 7 miles per second"

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Offline Tumeni

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Re: One degree of longitude
« Reply #31 on: December 14, 2018, 10:01:22 PM »
The OP starts from the premise of using google Earth.

If you go back to basics, with Norwood's method from the 1600s (summarised here by Bryson);

Quote
Starting with his back against the Tower of London, Norwood spent two devoted years marching 208 miles north to York, repeatedly stretching and measuring a length of chain as he went, all the while making the most meticulous adjustments for the rise and fall of the land and the meanderings of the road. The final step was to measure the angle of the sun at York at the same time of day and on the same day of the year as he had made his first measurement in London. From this, he reasoned he could determine the length of one degree of the Earth’s meridian and thus calculate the distance around the whole. It was an almost ludicrously ambitious undertaking—a mistake of the slightest fraction of a degree would throw the whole thing out by miles—but in fact, as Norwood proudly declaimed, he was accurate to “within a scantling”—or, more precisely, to within about six hundred yards. In metric terms, his figure worked out at 110.72 kilometres per degree of arc.

then ...

You surely must agree that the method hinges on the premise of the angle being drawn around a central point, and that can only be true of a globe. Where would you draw the central point on a flat earth?

The trigonometry hinges on the difference of two angles yielding the single angle drawn at the centre of an arc between the two points where the sightings were taken to the sun. Again, it has no meaning on anything other than a globe
=============================
Not Flat. Happy to prove this, if you ask me.
=============================

Nearly all flat earthers agree the earth is not a globe.

Nearly?

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Offline RonJ

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Re: One degree of longitude
« Reply #32 on: December 14, 2018, 10:05:24 PM »
There are many points that use latitude and longitude on the earth. These points are accurately placed on a map and accurately depict how things are laid out on the earth.  Now I can take those same latitude and longitude coordinates and calculate accurate distances between them using spherical trigonometry.  That means either the earth is spherical because the results are accurate, or spherical trigonometry is an invalid mathematical procedure.  These are two mutually exclusive things.   It's a done deal.  Sailors and pilots have for a long time used charts based upon a spherical earth.  Navigational calculations are made every day based upon spherical trigonometry.  Sailors don't get lost at sea.  Planes don't get lost on long overseas flights and run out of fuel because they are lost.  You just can't argue with success.  You can discuss the fine points and debate getting the last little bits of accuracy from a chart, but the very basic, rock bottom, facts are that the earth is a sphere.
You can lead flat earthers to the curve but you can't make them think!

Offline edby

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Re: One degree of longitude
« Reply #33 on: December 14, 2018, 10:40:08 PM »
We are missing the point of the OP. Rowbotham says:

Quote
The following is the true state of the question:--If the earth is a globe, it is certain that the degrees of longitude are less on both sides of the equator than upon it. If the degrees of longitude are less beyond, or to the south of the equator, than upon it, then it is equally certain that the earth is globular" (my emphasis)

So all that is needed to prove him wrong is to find any two positions of similar latitude and find whether the distance corresponding to 1 degree of longitude is less than the expected distance at the equator.

I have noticed (and Max Almond too) how GE tends to complicate the arguments unnecessarily. The argument is actually quite simple. See my posts above about road signs of the sort that say '100 miles to X'.

The OP starts from the premise of using google Earth.

If you go back to basics, with Norwood's method from the 1600s (summarised here by Bryson)

All true, but the question is the distance of 1 degree of longitude, not latitude.
« Last Edit: December 14, 2018, 10:44:56 PM by edby »

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Offline RonJ

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Re: One degree of longitude
« Reply #34 on: December 15, 2018, 12:59:27 AM »
I illustrated the fact that the distance between 1 degree longitude lines South of the equator is less than 60 nautical miles in two of my posts above.  Both of the examples were given by Rowbotham in his book where he just made a measurement or calculation error.  After the errors were corrected the example clearly showed that the earth is a globe.  It's a very simple concept to understand that the flat earth paradigm simply can't tolerate converging longitude lines South of the equator.   

Google Earth was used and you could clearly observe and read road signs and distances.  I tried a couple of examples doing that, but my results were inconclusive.  You need a nice straight East-West road in Australia of about 100 to 200 miles.  If you could read the road signs you could get a mileage figure and maybe match it up with the calculated mileage based upon the coordinates you also get from Google Earth.  I have done that between a couple points and can confirm that my spherical trigonometric calculations match very closely to the mileage you get on Google Earth. 
« Last Edit: December 15, 2018, 01:08:55 AM by RonJ »
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Offline RonJ

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Re: One degree of longitude
« Reply #35 on: December 15, 2018, 06:02:41 AM »
Here's another sample of measuring longitude between two points.  I got lucky.  There are two airports in Australia. The first one is in Adelaide and the other is in Rowra.

Adelaide   34 degrees 56' -- 50'' South |  138 degrees  31' -- 59'' East            Rowra   34 degrees 56' -- 30'' South   |  150 degrees  32' -- 40" East

Notice how there's only a 20 second difference in Latitudes.  That's about 1/2 mile difference at the most.  The distance was checked several different ways.  If you just went by the most verifiable way and drove the route you could expect a 715 Nautical mile trip.  If you flew airport to airport you could expect the distance to be about 591 Nautical Miles.  My spherical mileage calculations based upon the coordinates yielded the same 591 Nautical Miles.  Now, as Rowbotham says, let's do the math:  Difference in Longitudes is just a little over 12 degrees.  That means the worst case driving mileage 715/12 = 59.58 Nautical Miles per degree.  If you go the direct air route which is 124 Nautical Miles shorter you get:  591/12 = 49.25 Nautical Miles per degree.  That is very close to Rowbotham's prediction for a spherical earth. 

You can verify my figures yourself.  Airports have verifiable locations so pilots can do their flight planning and not run out of gas.  Maybe with a lot of work I could find some short cuts to reduce the driving mileage but this was just a simple example of what can be done.  If you went by Rowbotham's figure of 25000 miles of flat earth circumference at the equator figure, that would mean at 34 degrees South Latitude the distance between 1 degree Longitude should be around 90 Nautical Miles by the flat earth paradigm.  The worst case driving mileage calculations still comes out a whole lot closer to the globe earth rather than the flat earth paradigm.  If you go by the direct air mileages you are within 1 percent of the spherical earth figures even by Rowbotham. 

That's another one for Rowbotham ----  Round Earth: 3   Flat Earth: 0  (See the other examples in my posts above)         
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Offline Spingo

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Re: One degree of longitude
« Reply #36 on: December 15, 2018, 07:21:39 AM »
Longitude and Latitude isn't used by Google Maps/WebMercator to measure distances.

Have a read: The Earth is Not Round! Utah, NAD83 and WebMercator Projections

Quote
Latitude and Longitude are useless for measuring distance and area because the unit of length, degrees, is not held constant for longitude, except along parallels -- individual perfectly east-west lines.

...

Web Mercator's significant weakness is that measurements of distance and area in its native coordinates are completely unusable. Where accurate distance and area calculations are needed, web-mercator GIS data must be temporarily reprojected to a more suitable coordinate system (UTM NAD83).

It is admitted that the latitude and longitude coordinates of the spherical earth model is completely unusable, and that the data must be reprojected onto a local state plane coordinate system for accuracy.

You are trying to compare lat/long coordinates which are said to be "completely unusable."

Indeed mapping a spherical surface on to flat paper is a tricky prospect with plenty of room to introduce errors. Interesting web site. How do you feel Tom that the link you provided is basing all its prime data on the earth being a sphere? If you accept all the information on this web site it follows you will have to ditch Rowbotham and all your flat earth beliefs.
Thanks for the link as it reinforces how ludicrous the idea of a flat earth map is. One true data set equals the possibility of onetrue map.

Based on the article he quotes, Tom seems to be willing to trust a map generated from a UTM NAD83 projection, but he can't have it both ways. Earlier on I posted a map of the Falklands which is also generated via a UTM NAD83 (Zone 12N) projection (exactly the same one used in the article), so it should by Tom's reasoning be acceptably accurate. The problem is it shows a degree of longitude to be less than 70km wide, which means it's shorter than a degree of longitude on the equator, which means Rowbotham, by his own statements, faced with that evidence, would have had to admit that the earth was "globular" as he put it.

Whether Tom accepts or understands that a UTM NAD83 projection is entirely based on a globe earth or whether he does not, if he trusts that a map produced via this projection is accurate, then OK, here's just such a map and it shows the earth is at the very least "globular".

As I have mentioned previously, the production of accurate maps is much more complex than one would imagine. Here is quite a good guide from the OS in the UK that explains about how they use their GNSS data sets.

https://www.ordnancesurvey.co.uk/docs/support/guide-coordinate-systems-great-britain.pdf?awc=2495_1472758581_2be7907c343c32b09a8d5171103197d7

Once you have some inkling into the complexity of map production, it really makes you realise how ludicrous some flat earthers are when they claim to be working on producing a flat earth map!

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Offline stack

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Re: One degree of longitude
« Reply #37 on: December 15, 2018, 09:02:06 AM »
Based upon the evidence presented in this thread, it seems that the conclusion is:


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Offline Tom Bishop

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Re: One degree of longitude
« Reply #38 on: December 15, 2018, 11:07:21 AM »
Edby,

NAD doesn't use a Longitude or Latitude coordinate system.

The coordinates on the plane survey maps are simple integers.

Latitude and Longitude is a system for a globe in these models, and is not native to the planar maps. It is a spherical coordinate system.

If you are figuring out what the globe's Latitude and Longitude would be for the State Plane Coordinates you are interpreting a plane onto a globe, for the location of that plane on the globe model.

Here we see the State Plane Coordinates (SPC) and the associated Lat and Lon for the location on a sphere.

wvgis.wvu.edu/conference/2014/Wed_Track3/Iskic_NorthAmerican_Datums.pptx



The SPC coordinates look much different than the Latitude and Longitude's spherical coordinates.

This ad-hoc system they have is part sphere and part plane. You are arguing on basis of the spherical coordinate piece of it to justify your spherical earth.

I don't even hold that the longitude lines would widen, myself, as I have always been a proponent of the Bi-Polar model. I just see that the analysis on this matter appears to be flawed.

Rowbotham is actually referring to manual ways to find longitude, as was done in his time... The spherical geographical model that is associated with these planar maps is literally a sphere.
« Last Edit: December 15, 2018, 11:19:15 AM by Tom Bishop »

Re: One degree of longitude
« Reply #39 on: December 15, 2018, 11:13:59 AM »
We are missing the point of the OP. Rowbotham says:

Quote
The following is the true state of the question:--If the earth is a globe, it is certain that the degrees of longitude are less on both sides of the equator than upon it. If the degrees of longitude are less beyond, or to the south of the equator, than upon it, then it is equally certain that the earth is globular" (my emphasis)

So all that is needed to prove him wrong is to find any two positions of similar latitude and find whether the distance corresponding to 1 degree of longitude is less than the expected distance at the equator.

I have noticed (and Max Almond too) how GE tends to complicate the arguments unnecessarily. The argument is actually quite simple. See my posts above about road signs of the sort that say '100 miles to X'.

The OP starts from the premise of using google Earth.

If you go back to basics, with Norwood's method from the 1600s (summarised here by Bryson)

All true, but the question is the distance of 1 degree of longitude, not latitude.

Couldn't agree more. How wide is a degree of longitude south of the equator compared with on the equator? A really simple question to ask, very easy in the modern world to answer and if the answer is smaller to the south, then one of Rowbotham's central claims falls apart and by his own reasoning the earth is globular.

No need to complicate the discussion beyond the central question (and I admit I did get sidetracked myself trying to address Tom's spurious UTM NAD83 map arguments - sucked into that one!).

The New Zealand pic to me is great, it's so far south that the measurements are unambiguous and the road sign is there for all to see.

The fact that Tom seems to have withdrawn completely from further discussion and no other flat earthers seem willing to address the issue at all says nail on head, hit to me all day long.