I read the manga rn my second time and I realized in the shelter arc that something about the coordinates seems wrong.
They found a handwritten letter from Minerva with the coordinates of Goldy Pond. Yuugo has read the letter and was there before. So how could it be the same coordinates for Yuugo and for the Gracefield kids if Gracefield is 00-00? Shouldn't it be other coordinates for Yuugo and the Bell kids if Glory Bell is on their map 00-00.
And if really the whole Minerva coordinate system based of 00-00 as Gracefield, could the Glory Bell kids found out how the system works?