A Turtle Pose is a special type of compass found only in the seventh movie.
It consists of a baby sea turtle in a small pool of water. These are used to navigate to Mecha Island which is located in the Grand Line.
The reason Log Poses are not used to navigate to Mecha Island is because it is actually a giant sea turtle that lacks a magnetic field. This compass points towards the moving island.
- ↑ 1.0 1.1 1.2
One Piece Movie 7,
The Turtle Pose is used for the special island.