How come...

How come when mapping and surveying over a large distance, you have to factor in equations for the curvature of the earth otherwise the results are wrong?
If the world was flat then none of these equations would be needed, but they are....

How come when mapping and surveying over a large distance, you have to factor in equations for the curvature of the earth otherwise the results are wrong?
If the world was flat then none of these equations would be needed, but they are....

Since it's unlikely that anyone around here has actually mapped large areas, please explain what equations you are talking about and how they apply.

http://books.google.co.uk/books?id=BZYOAAAAQAAJ&pg=PA42&lpg=PA42&dq=surveying+correction+for+earth+curvature&source=bl&ots=Uu8hstfHPs&sig=65MeeZSGZ6t4BYXPxWsH_moB3OU&hl=en&ei=AJwtStu5K5TQjAe0yOj1Cg&sa=X&oi=book_result&ct=result&resnum=4#PPA42,M1
Page 42 onwards. Pretty simple explanation of the correction needed.
Plus, if the earth is flat, then how are there satellites, such as GPS, which isn't broadcast from a tower, as the amount you need etc wouldn't be inrange of a tower, nor would that method of measuring work.
Plus, if satellites aren't real, how do you explain imagery from stuff such as Landsat or AVHRR where you can actually see alterations you make to the scenery. Not to mention the radiometric quality of the pictures are too high for it to work on a plane, as well as you can intercept the return signals from the satellites, showing they aren't from a plane. And the spatial resolution is too high to be from a plane, with the continued coverage & massive swath widths would be needed to be taken from an altitude greater than any plane can go, or for that length of time. Plus, with the amount of sensors that some satellites carry e.g. ENVISAT, there is no way they could be mounted on a plane.

Well, anyone?
If you can't disprove this you guys believing in a flat earth are kind of screwed.

http://www.sacred-texts.com/earth/za/za05.htm and onwards.

http://www.sacred-texts.com/earth/za/za05.htm and onwards.

Yeah, that proves nothing as the guy/idiot writing the book doesn't take into account the increasin angle of the plane to the earth, nor if it is spherical that it would then have to come back on itself.
Plus, if the earth is flat, why are these corrections needed? And they are needed otherwise the measurements are out by miles. Literally.

How do you know?

How do you know?

Because I've surveyed large areas using EDM. You have to include corrections for the earth's curvature, otherwise the measurements are out by a large amount.

Out of what?

Out of what?

The results aren't right basically.
You travel from point A to B, giving point A an arbitrary height, of say 100 (You can use OSBM to get the actual height, but that is irrelevant at the moment). When travelling you take measurements of points along the way, giving you either a raise or fall in the land. When you arrive at point B you have a height.
To make sure it's correct you then travel back to point A from point B. With the results you subtract the first readings from the second and the figure left over is the difference between the two rounds of height measuring. Millimetre accuracy is what you want, and if you don't take curvature into account over a large area, the margin of error is in the meters.
And this method is the standard surveying method used in construction and any surveying work.

What height are you talking about?

What height are you talking about?

The height of the land, but it doesn't actually matter in the example. If you just give any random point a height of 100m or any arbitrary number, when you come back from travelling from point A (anywhere you deem as point A) to point B (anywhere you deem as point B), you need to end at the starting value (100m or whatever height you have chosen, whether it is the true height or not, as you can actually calculate the true height by then just surveying to a point with a known height).

But how do you determine the height of the point on the ground you are currently on?

But how do you determine the height of the point on the ground you are currently on?

(Point A) EDM on tripod shoots to a prism on a tripod. Height of tripods are subtracted. Height of EDM on tripod considered 100m for this example.
This process is repeated until point B is reached.
Same is done from point B to point A.
Difference in the measurements are calculated. Over a large distance, if curvature of the earth is not factored in, then there is always an error. The constant error can be showed to be incorrect by measuring said points to OSBMs. If you want to query how they are calculated, look them up.
This is the way heights/measurements for buildings prior to GPS (which does exist) were calculated, so is hardly flawed.

Well, since I am not familiar with the slang in surveying, I wikied EDM and came up with meaning 'Electronic Distance Meter, which, together with a Theodolyte, makes up a Total Station. However, since electronics are involved, it means the Total Station does some calculations. We are interested in the Principles of operation of such a device. That means, tell us what quantities it measures and how and what equations it uses to calculate what.

Well, since I am not familiar with the slang in surveying, I wikied EDM and came up with meaning 'Electronic Distance Meter, which, together with a Theodolyte, makes up a Total Station. However, since electronics are involved, it means the Total Station does some calculations. We are interested in the Principles of operation of such a device. That means, tell us what quantities it measures and how and what equations it uses to calculate what.

Crack out an old theodolite and a measuring staff. That removes any dubious electronics, and you'll come up with the same need for the corrections.
How they work is very complex so spend some time looking it up. Either way, they are what are used to ensure walls line up in construction, so again, the workings of them are correct, and essentially all they do is measure the time a laser takes to travel from the EDM to the prism.

Actually, I will not read about the construction of the theodolyte. I wanted you to present us with the principles of measurement. But, you chose to say it's complicated and it's correct. Okay, then ENaG is also correct. Goodbye.

Actually, I will not read about the construction of the theodolyte. I wanted you to present us with the principles of measurement. But, you chose to say it's complicated and it's correct. Okay, then ENaG is also correct. Goodbye.

Well I gave a brief summary of it saying it measures a the time it takes a laser to travel from point A to B, similar to radar.
And just to avoid any "it can't be right" accusations, I also mentioned that it's the method used to make buildings.
Point is, how does FET explain this?

If you only know the distance from a point, that defines a sphere in 3D, which gives a a complicated intersecting line with the Earth's surface, depending on the shape of the terrain.

This suggests you know nothing about surveying so stop trolling.

If you only know the distance from a point, that defines a sphere in 3D, which gives a a complicated intersecting line with the Earth's surface, depending on the shape of the terrain.

This suggests you know nothing about surveying so stop trolling.

That makes no sense, and considering I do surveying, I think you need to read up about something you clearly know very little about.
Care to elaborate and what you are trying to say, as again, it makes very little sense, as the round earth correction is considered after the readings are taken, and there is no intersection with the earth, as the only points measured are on the surface.

guys, tha conspirators went skydiving and decided to photoshop this.

guys, tha conspirators went skydiving and decided to photoshop this.

.....any proof its shopped?

It shows the earth as curved - definitive evidence that it is a fake!

.....any proof its shopped?

sarcasm detector.

Quote from: mazty88 on June 11, 2009, 07:10:52 AM

.....any proof its shopped?

sarcasm detector.

I can't actually tell who on this site is serious or not, as some of the 'valid' arguments for FET are so absurd.
So just in case you are serious about it being shopped, any evidence?

Quote from: heyethan on June 11, 2009, 09:30:12 AM

Quote from: mazty88 on June 11, 2009, 07:10:52 AM

.....any proof its shopped?

sarcasm detector.

I can't actually tell who on this site is serious or not, as some of the 'valid' arguments for FET are so absurd.
So just in case you are serious about it being shopped, any evidence?

I'm not being serious. I am often satirical when making a point, which is probably a bad idea on a website like this.