Joshua asks this question in order to encourage the Israelites to take possession of the land. AT: "For long enough, you have put off ... has given you." (See: [[rc://en/ta/man/translate/figs-rquestion]])
# the land up and down
The words "up and down" mean in every direction. AT: "the land in every direction" or "throughout the land" (See: [[rc://en/ta/man/translate/figs-idiom]])
# write out a description of it with a view to their inheritances
This means that they will describe the portions of land that each tribe would like to receive for an inheritance.
The land that they are to survey is spoken of as if it were an inheritance that each of the tribes would receive as a permanent possession. (See: [[rc://en/ta/man/translate/figs-metaphor]])