I am creating a cartographer character, in my group's upcoming Out of the Abyss game, who was hired to create a map of the Underdark. I imagine that would involve a skill check each time he adds to the map. Which skill would be used for making a map, Nature, Survival, or just a straight-up intelligence roll?
Drawing a map does not require any rolls. It's listed among Activities While Travelling: Other Activities, see p. 183 PHB
Someone who is hired for creating a map would likely be proficient with the appropriate Artisian tools for crafting maps though: Cartographer's tools (p. 154 PHB)
Crafting a map after collecting the "data" would require a Ability check adding the proficiency bonus, if proficient in Cartographer's tools.
2 Abilities come to mind (DM's choice):
- Dexterity: Crafting something artistically
- Intelligence: Deriving the layout from available data