# Round World Vs. Flat world

## Recommended Posts

Hi, I'm fairly new at this, and I've noticed some of the mystery caches tell you to assume "the world is round" or to assume "the world is flat". What does this mean in terms of solving the puzzle or projecting waypoints?

Thanks.

It may have something to do with map projections. Beyond that I have no idea.

Hi, I'm fairly new at this, and I've noticed some of the mystery caches tell you to assume "the world is round" or to assume "the world is flat". What does this mean in terms of solving the puzzle or projecting waypoints?

Thanks.

I don't know about those specific caches, so my information might not relate.

Since the world is round representing the map as flat distorts distances between two points. It can also change where two line intersect. For example, if you are given 4 location and asked to draw an X between them, you would get two different locations depending if you are looking at a globe or looking at a flat map.

Does anyone know if there is a setting on the GPSr that compensates for these assumptions?

My thought is that they are mentioning this to simplify things. The world is far from round, and even lakes aren't flat....

Can you give some examples of the caches that are using this verbiage? Seeing it context will help in coming up with reasonable responses. We aren't going to be solving any puzzles for you but we can at least help you interpret what you are reading. Maybe...

Archived example Vincenty's Dilemma,

Jim

Archived example Vincenty's Dilemma,

Jim

Yep, math and geometry can be great fun. Good example.

To the OP: what examples do you have?

OMG the world is ROUND????

Does anyone know if there is a setting on the GPSr that compensates for these assumptions?

UTM coords assume the world is flat. This is why you have UTM regions (or whatever they call them).

WGS84 assumes the world is round(ish). No regions.

OMG the world is ROUND????

No no.. assume the world is round. Any right thinking person knows that the world is pretzel-shaped. That's why many things are so twisted.

Thanks for the help. I always wondered why the world smelled constantly of pretzels.

OMG the world is ROUND????

I take great comfort in this epiphany! I finally understand why I couldn't find a single edge.

Pete

This is the cache that first got me all confused:

TESTING TO DESTRUCTION

http://www.geocaching.com/seek/cache_detai...ae-3f2fe43e8cd2

It's meant to take a plane geometry problem and cast it as a real-world problem without the added complexity.

Unfortunately, it introduces some ambiguity into the puzzle. Which north are you supposed to use for the (very precise) azimuth? Magnetic north? That doesn't make sense, as the declination is only precise to about a half degree, so the bearings cannot be measured from magnetic north to that precision. Grid north? No, he mentions declination. Should you accommodate for the grid skew in the calculations or not?

Probably, given the attempt to fit the plane-geometry problem into the plane, the author means to use whatever declination is published (to the nearest half degree) , to treat it as infinitely precise, and to assume that grid north does not change over the scale of the problem.

I guess I am not overly impressed by the puzzle. The fact that the world is (mostly) round makes these problems a lot more difficult, even when the cache owner tries to remove it!

Edited by fizzymagic
OMG the world is ROUND????

No no.. assume the world is round. Any right thinking person knows that the world is pretzel-shaped. That's why many things are so twisted.

And geocachers are the salt of the Earth.

If you're assuming the world is round, you also need to make assumptions about which side of the curve we live on.

I remember reading something about folks who postulated that the world is round, but we live on the inside of a hollow sphere -- like inside a giant Kinder Egg.

Edited by CacheNCarryMA

I always wondered why the world smelled constantly of pretzels.

i thought that was just my bedroom.

## Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

×   Pasted as rich text.   Paste as plain text instead

Only 75 emoji are allowed.

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
×
• Create New...