It will show main headings in the document. You can then click on them to jump to that part of the document. This is much faster than scrolling up and down through the document.
Planets are not used as a navigation aid because they are not in a moving position at particular times of the year.
For navigation
Written documents are useful in setting up a government because it is like proof.
written documents are useful because they allow the government to have proof of laws and agreements.
Compass
To print documents.
Navigation and migration .
Magnetoception is a type of navigation used by some animals. It is navigation that uses electromagnetic fields, and has been observed in bacteria. It is useful because scientists might be able to come up with different types of navigation.
Rivers in Europe are useful for internal navigation because they do not have sudden breaks and connect various towns and cities.
The pronoun 'that' is functioning as a relative pronoun, introducing the relative clause 'that will be most useful'.The relative clause is providing information 'relating' to its antecedent, 'documents'.
these
It is useful because it is directly above Earth's north pole so if you were traveling north, you would know what to follow