What does the in-game map in Tomb of Annihilation do in regard to navigation checks?

Question

I'm running Tomb of Annihilation as a first-time DM and I don't know how to handle the map that their patron gave to the party. Only parts of this maps are already filled in, but this does means that for the first chunk of the adventure, the party is within filled-in territory. I plan on filling in the map as they go along (one of the players has navigators tools and another is an Outlander) but I think I might run into a problem:

On a daily basis someone has to make a Survival check which prevents the party from getting lost. Mechanically, the book says nothing about if having the map - specifically being in the filled-in areas of it - does anything to these checks. No advantage, no lowering of DC, nothing. I'm almost certain that my players are going to bring this up and I don't know exactly how to handle it.

The party consists of a druid, a sorcerer, a barbarian and a cleric - who will most likely be doing the check due to his high Survival. They also have a guide who might be able to give them advantage on the Survival check.

Mainly, I'm worried about making navigation either too challenging or not challenging enough. If I give out advantage for the navigation check every time then it feels like a needless roll, if I don't then I'm worried my players will get annoyed by the map or guide not being useful.

Answer 1

Nothing, mechanically

The ingame map, as it's introduced in the book, does absolutely nothing for your players in terms of navigation, other than allowing them to point to where they want to go in the first place.

My players too complained that the guide isn't particularly useful, because their own survival check was higher than that of the NPC guide they had along. They continued to complain about how useless their guide was, until they got seperated from the guide and suddenly couldn't figure out what jungle food was edible, didn't have somebody to tell them the customs of the Batari Goblins and didn't know what direction locations not on their map were.

If your players complain that the map isn't useful, simply take the map aspect away, it's not truly needed.

If you want to keep using the map but they complain it doesn't help them, take the map away for a second and ask them which direction they need to go to reach the Peaks of Flame and Smoke from their current location, making a stop for supplies at Camp Vengeance. Suddenly a map doesn't sound quite as useless, because a map helps you know -where- you want to go, while navigation checks handle the -how- you get there.

Travel in the jungle isn't difficult because you don't know where you are going, but because it's simply not always possible or feasible to take the direct route. Trying to take a shortcut and ending up on the wrong tile because of a bad roll is easily described as the forest looping around and leading to a dead end, map or no map.