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


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).




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

