

So, when you travel the Grand Line normal navigation methods don't work
because of the chaotic nature of place. Compasses just spin randomly, the
weather can change without any warning, currents can make a ship change course
without the crew even realizing etc.

For this reason, pirates who attempt traveling the Line rely on a Log Pose, a
device that always point to a specific "next" island on a specific route.
After crossing the Red Line again and entering the "New World" the Log Pose is
then upgraded to handle the even worse conditions: we go from a single needle
to three (because some island may just "decide" to become unavailable "because
reason").

If you keep following the Log Pose you will eventually reach a "Final Island":
Lodestar.

[![enter image description
here](https://i.stack.imgur.com/TmOki.png)](https://i.stack.imgur.com/TmOki.png)

And then... your Log Pose stop working. There is no "next" island to point to,
so the device you relied up so far suddenly becomes a decorative piece of
furniture.

After you reached Lodestar, you are supposed to discover about the existence
of the four Road Poneglyph (assuming a random guy on Zou didn't spoil you
before). Using the four Road Poneglyph you are supposed to locate four points
on the map...

[![enter image description
here](https://i.stack.imgur.com/JDPT1.png)](https://i.stack.imgur.com/JDPT1.png)

and Laugh Tale is supposed to be found at the intersection of those four
points.

So basically, Roger crew:

  * followed the Log Pose up to Lodestar.
  * somehow managed to "go back" from Lodestar to the previous islands where the four Road Poneglyph were located (without any way to know in advance that they would need to return there).
  * used the info from the four Road Poneglyph to find Laugh Tale.
  * _somehow managed to reach an arbitrary "island" in the middle of nowhere that no existing Log Pose points to in a place where we have been told so far the only way to reach some point is to have something that points there._

Let's assume that Roger was able to "backtrack" in the Grand Line using
multiple vibre cards and Eternal Pose that the crew strategically kept on hand
during the journey (btw good luck crossing the red line without a Eternal Pose
for Fishman Island, apparently that is the only safe place to travel under the
mountains) IF the "Laugh Tale is found at the intersection of the four places
indicated by the Road Poneglyph" is to be taken **literally** as the picture
above implies (picture actually taken from the show) this means that to reach
Laugh Tale you have to reach an arbitrary set of coordinates in the sea,
without any modern GPS systemm, without a working compass, in a sea where
apparently you can even be sure you are going in a straight line and where
star based navigation just doesn't seem to work "good enough" to be usable
(for example during the Alabasta arc Chopper mentions he couldn't see any star
at night from his home island because of the permanent winter weather
conditions, and Enies Lobby is **literally** stuck in an "eternal day").

....  
....  
....

You see where this is going.

How can anyone be able to reach _47°9′S 126°43′W_ under such conditions? And
to be fair... how did all the pirates that "gave up" backtrack the line to
return to their home sea (see: Don Krieg, Zeff) - where they just crazy
prepared and kept an Eternal Pose for all the mayor island during their
journey onward (this would make Nami suddenly look like a pathetic newbie
since she is never shown planning for this... it is "forward or die" for the
Straw Hats...). Either the inability to reach a set of specified coordinates
in the Grand Line is _**greatly exaggerated**_ or it should be impossible to
reach any point you don't have a Log Pose pointing to.

Am I missing some obvious caveat that could explain this? Are my initial
assumptions actually wrong? Or should we just accept that this point has no
actual explanation right now and may become relevant in the future?

* * *

Short version:

At the start of the Grand Line we are explicitly told that regular compasses
don't work and implicitly that celestial / star based navigation doesn't work
either because of the extreme chaotic conditions of the place (notice: there
is even a place - Enies Lobby - where it is _**always day**_ ) and you have to
use Log Pose that points to specific places to get around. Later, under the
same restrictions, we are told that to reach Laugh Tale you have to find out
its location and then travel to those coordinates without anything that points
there.

Is there any indication of how that is possible so far in the plot? How can
you reach any point even with a map if we are told that the Log Pose is the
only reliable way to know which direction you are going since traditional
instruments can't work (sextants, compasses, celestial navigation etc).


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one-piece
Can you reach any know arbitrary coordinates in the Grand Line without a Log Pose pointing there?


One thing to consider are [South
Birds](https://onepiece.fandom.com/wiki/South_Bird). It was a big deal during
the Jaya arc that the Straw Hats needed to head due South from Jaya to the
Knock Up Stream. They couldn't use their log pose because the log pose only
points directly at the next island (Skypiea) with no reference to the compass
directions. Nor normal compasses which don't work in the Grand Line due to the
magnetic fields of the individual islands causing the needle to go crazy.
They're told to wrangle a South Bird and leverage its inexplicable ability to
always point South.

South Birds clearly have some mechanism which allows them to determine compass
directions unaffected by the magnetic fields of the islands of the Grand Line
and would be invaluable for navigating the GL without log/eternal poses (E.G.
sailing towards an arbitrary set of coordinates) which honestly beggars the
question why they aren't more widely used.

Granted just having a working compass is only half the solution, knowing which
way is South is well and good but doesn't tell you where you are. This would
require tools like
[astrolabes](https://en.wikipedia.org/wiki/Mariner%27s_astrolabe) or
[sextants](https://en.wikipedia.org/wiki/Sextant) which can determine Latitude
and Longitude. As far as I recall, we've never seen anyone ever use such tools
even though they should work (you only really need it, the sun and the
horizon) and they'd be needed to navigate even outside the Grand Line (maps
and a compass aren't very useful if you're out at sea and don't know where you
are and therefore what direction your destination is). Although, since sailors
can navigate the Blues just fine we can probably assume they have some way of
knowing where they are, which, supplemented by maps and a compass should be
good enough to find a specific spot in the oceans


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> Am I missing some obvious caveat that could explain this?

Yes, [Maps / Sea Charts](https://onepiece.fandom.com/wiki/Map). This is what
makes [Navigators](https://onepiece.fandom.com/wiki/Navigator) so important to
crews even with the existence of Log Poses.

To quote the most relevant parts of the wiki (emphasis mine):

> In the world of One Piece, **maps are an essential tool for navigation** ,
> as they often depict the geography of an individual island, a group of
> islands or even an entire ocean (in which case, they are sometimes referred
> as sea charts). In sailing, **it is usually the duty of navigators to read
> and interpret maps during voyages, in order to establish safe navigation
> routes and avoid natural hazards or getting lost.**
>
> The first relevant map shown in the series was one of the Grand Line, which
> belonged to Buggy, but was stolen by Nami and subsequently used by the Straw
> Hat Pirates to enter the Grand Line through Reverse Mountain. Another
> important map was of Skypiea's, which Luffy managed to find in the old
> remains of the St. Briss and allowed the Straw Hats to consider the idea of
> Sky Islands.

Nami's entire arc revolves around maps - her dream is to make a map of the
entire world, and she was exploited by Arlong due to her great ability to
understand and create them.

There may not be any "arbitrary coordinates" in the One Piece world since they
don't have GPS, but to reach Laugh Tale based on descriptions from the 4 Road
Poneglyphs is exactly what a Navigator is skilled at doing.

This would also explain how Roger's crew backtracked. We don't have
confirmation about who on the crew was a Navigator, but since they were the
first to circumnavigate the world and find Laugh Tale, it should have been
easy to go back the way they came.

[Eternal Poses](https://onepiece.fandom.com/wiki/Eternal_Pose) are said to
cost a fortune to purchase, so it is probably not used by most crews. Vivre
cards do remain a last ditch option, but they only tell you the direction and
not anything about distance or obstacles. So it is likely they too would be
insufficient / dangerous without some kind of Navigator.

* * *

In the anime, there seems to be a filler arc on the way from Zou to Whole Cake
Island which explicitly mentions Nami plotting the route using a map ([Episode
775](https://onepiece.fandom.com/wiki/Episode_775)). Not included in the main
answer since this isn't 100% canon, but it's certainly believable (though one
could argue that Nami was in possession of Big Mom's vivre card).

In case you are wondering how no one just came across Laugh Tale (given enough
time) if people can simply traverse the sea using maps, I would **speculate**
this is due to 2 reasons:

  1. It is in an unmapped area that has very low traffic
  2. It is hidden by some means that can only be countered with information from the Road Poneglyphs

It shouldn't be very hard for someone like Kizaru to just go across the entire
sea grid by grid since his [Pika Pika No
Mi](https://onepiece.fandom.com/wiki/Pika_Pika_no_Mi) allows him to travel at
"the speed of light". Others like Aokiji (who can freeze the water surface) or
Brook (who runs on top of water) might take an impossibly long time, but that
isn't a concern for Kizaru. Thus, it is likely the island is hidden somehow
beyond an unknown location.


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Four eternal poses should do it. You can use the vectors of the four poses as
a low-tech combined GPS system locally from between the four islands. If you
can get to at least one of the islands (which having even one eternal pose can
help you do) then you can find the one piece if you know the location between
the four points on the map. The way you calculate where you are is taking all
of the eternal pose vectors and drawing lines from their islands on a map at
regular intervals until your four vectors align at the target point.
Technically this should be possible even with only three poses. The challenge
is that if you need to know the height (or depth) you need a fourth vector to
predict a 3D location.

For similar reasons, if they can make use of birds or flying machines they
could avoid needing to do any of this and just fly high enough that they can
localize the point they're looking for from the sky.

Another way, which you might not have considered is making use of the
stillness of the calm belts. If you reach the calm belt and can assess which
side of the grand line you are on, you can simply travel straight along the
calm belt by using an external force instead of the wind and waves. Presumably
then any log pose or compass or other method of navigation should get you back
on track regardless of where you end up but there would be no way to know how
far you've gotten without some serious engineering work and traditional
navigation methods would fail as soon as you entered the grand line again) -
another way to localize yourself, a vivre card, or an eternal pose is highly
preferable. It is known that various individuals have multiple ways to cross
the calm belt from lining ships with seastone to just being incredibly
powerful (and able to defeat sea kings). Given the Sunny's ability to launch
itself through the air, among other various feats, with some improvements, I
suspect it could survive this method.

I should also mention that four vivre cards for four members of the Strawhats
or their allies would be sufficient for them to use in place of eternal poses
should those individuals head to the four islands. Not sure how this would
work for someone like Buggy who can split themselves into multiple pieces.
Maybe he could somehow use a vivre card in another way with four parts of
himself to find the one piece? Probably easier to use eternal poses though.


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