Offline wtbofnc

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Grid Referencing system that all Navigation systems use
« on: January 17, 2016, 09:52:46 PM »
Why are grid lines on a map perfectly square?   Shouldn't they be a different shape if the earth is ROUND?

Re: Grid Referencing system that all Navigation systems use
« Reply #1 on: January 17, 2016, 09:59:58 PM »
because squares are easy to work with, and they're based on flat map projections. One of the most common ones, UTM, splits the world into six zones and uses a Mercator projection in each zone.

i hope you're a troll because this is one of the worst arguments for a round earth i've ever seen.

Offline wtbofnc

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Re: Grid Referencing system that all Navigation systems use
« Reply #2 on: January 17, 2016, 10:04:45 PM »
You totally dodged the question.  Grid Squares are perfectly square.  If the earth is round, why aren't the lines on a grid square either bowed, canted slightly or in a hexagon or octagon shape?  Also, since you want to look a little intelligent. Answer this:   Why are these grid squares only used on land?   If the earth is round, why not incorporate this grid system for every navigation system on the ROUND earth?    Woot Woot!

Re: Grid Referencing system that all Navigation systems use
« Reply #3 on: January 17, 2016, 10:19:33 PM »
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If the earth is round, why aren't the lines on a grid square either bowed, canted slightly?

I answered this already:

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they're based on flat map projections. One of the most common ones, UTM, splits the world into six zones and uses a Mercator projection in each zone.

map projections distort the shape of the Earth. The mercator projection distorts it in such a way that it can be divided perfectly into squares. this is what UTM is based on. If you had even bothered to do a cursory google search first, you would have realized this.

typically, these types of grid squares are only used over relatively short distances, when the region can be approximated as flat with relatively little error. Over larger distances, the curves in these gridlines are perfectly visible:



Other shapes aren't used because, as I said, squares are really easy to work with. Octagons don't even tesselate a plane, so they'd be totally useless. Also, I don't know why you think they're only used on land. As you would be able to see if you had looked at the UTM wikipedia article I linked, UTM can be used anywhere in the world, even over oceans.
« Last Edit: January 17, 2016, 10:21:11 PM by rubberbands »

Offline wtbofnc

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Re: Grid Referencing system that all Navigation systems use
« Reply #4 on: January 17, 2016, 10:22:00 PM »
Look at the map you posted!   It's missing the top and bottom of the map!   How do you use this grid system in the North and South pole?  YOU CAN'T!   

Rubber-B, I'm on your side...  I'm trying to dragnet the RE trolls in on this one...  This is some serious shit.  This is an argument that you can have with any Round Earther...  Why would you show a Globe in Every school with Latitude and Longitude lines.  But then when it comes to building a grid referencing system, you use something totally different?  This is my argument.  Most people have absolutely no education in this subject.  You will be arguing with rocks.  Which, honestly are smarter then they are!   ;

Seriously though, the only squares I see on that map are the ones nearest to the Equator!   
« Last Edit: January 17, 2016, 10:27:25 PM by wtbofnc »

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Offline LuggerSailor

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Re: Grid Referencing system that all Navigation systems use
« Reply #5 on: January 17, 2016, 11:16:33 PM »
I take it you've never used a map/chart for navigation. Plotting a course and steering the same.
Following roads while driving a car isn't the same as trying to navigate across the sea.


The property of the Mercator projection map that made it useful to navigators is that it preserves angles. Lines of constant compass heading (called rhumb lines by sailors) are straight lines on this map. Say you're in Vancouver and want to get to Honolulu, Hawaii. You don't have GPS, just a compass.



Just draw a straight line on the map between where you are and where you want to go, and measure the angle (almost exactly 45 degrees in this case). So (after a small detour around Vancouver Island) you head southwest, and off you go. If you keep heading in this direction, you ought to get there.

As you point out, the distortion in the far north and the far south makes things a bit awkward but the arctic ice-cap and the antarctic continent make sailing a bit difficult.
LuggerSailor.
Sailor and Navigator.

Re: Grid Referencing system that all Navigation systems use
« Reply #6 on: January 17, 2016, 11:50:45 PM »
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Look at the map you posted!   It's missing the top and bottom of the map!   How do you use this grid system in the North and South pole?  YOU CAN'T! 

...right. If you want to look at the North or South Pole, you use a different map. They're not even missing, they're just spread out somewhat more than in real life (but nowhere near as much as they would be on Mercator, which does have to be clipped at the poles). Just like if you want to navigate New York City, you use a map of NYC, and then you can use a different map if you want to navigate London. Maps don't have to show every bit of the world at once. I didn't think that was a difficult concept to understand.

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Why would you show a Globe in Every school with Latitude and Longitude lines.  But then when it comes to building a grid referencing system, you use something totally different?

They aren't different. If you zoom in enough on a globe, latitude and longitude lines make almost perfect squares. A grid of squares, one might say. That's what you're seeing on maps with square gridlines.

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Seriously though, the only squares I see on that map are the ones nearest to the Equator!

Yes, because this map is a Robinson projection, not a Mercator projection. On a Mercator map, latitude and longitude lines make perfect squares. That makes it useful for navigators. It also makes it inaccurate around the poles. The Robinson projection preserves the sizes and shapes of landmasses better, at the cost of having curved longitude lines. You asked earlier why the gridlines aren't curved -- well, on this projection, they are curved. And when they aren't curved, it's not because the world is flat, it's because the projection is flat, and has certain properties.
« Last Edit: January 18, 2016, 04:32:30 AM by rubberbands »