Magic Mushroomcloud:
Hiya.
As someone that's never GM'd before but is curious to try, let me ask you folks: just how important are detailed maps in a game?
Hi. As the others I would say "it depends". [sorry this got a bit long]
First off it depends if you mean in real life or here on rpol.
IRL it is much less important as the players can simply ask if unsure and get an instant reply "How far am I from the car" or "Can I reach the orc this turn?". In fact, I am of the opinion that a battlemap IRL might actively get in the way of the story. Once you put down a battlemap players tend to go into boardgame mode and forget everything about roleplay and only do roll-play. The game also tends to slow down the game and make it lose dramatic tension. So, when playing IRL I try to minimize my map use. And when I do need them, make do with hastily drawn sketchy outlines. This is also to keep the images in our head where they are much more alive. Once you have a detailed map and especially if you have miniatures, players tend to forget the images in their head and only see what's in front of them - which will always be less impressive than what you can picture with your imagination.
But, I suspect that you are talking about rpol ;)
---
On rpol maps are much more important as the players can't get a quick instant reply to a question. And it doesn't take away from the mental images as you do not have the map in front of you in the same way.
But, that doesn't mean you have to have it, nor that it have to be detailed in any way. But again it depends.
For instance, here on rpol I tend to run battle heavy games, to the point where the battle is the focus of the game, and everything around it is fluff to link the battles. The battles are the places the characters get to play out their strength and weaknesses, show their individuality and make important decisions. So, of course in those game I need a good map just as much as an investigation game needs a detailed setup so the players can solve the mystery. It becomes important to have lots of different object on the map the characters can interact with and allow them to choose between depending on their abilities and personality. That said, the map could as easily be a black and white MSpaint drawn map with a hexgrid overlay. but, since this IS the focus of those games I tend to make a lot out of the maps as it makes the game more exiting and alive.
But, in any game where combat isn't the focus, it shouldn't be necessary. And as for IRL games a battlemap might ruin dramatic tension. For instance, in a zombie survival game it might take away a lot of the tension to know exactly how many yards the zombies are from you exactly how many there are.
In general I also feel that "games with guns" tend to work better without a map. Or, rather, "games with guns" often run into situations that are difficult to portray using maps. A firefight in a staircase. A long-rang encounter with 100s of yards in-between the combatants, an urban combat with people in windows on top of houses, inside buildings an down a street in cover behind cars. All of these situations work better without a battlemap.
Another argument for not needing a map is that unlike IRL if you make a detailed description, the players can always go back and reread it if they are unsure. Where IRL people might overhear or misunderstand something you say.
The only place I think it would be unwise to avoid maps is if melee-combat is somehow important to the game. As all the rules for weapon reach and facing is very important in melee and cumbersome to explain and keep track of without a map. But, thats assuming you are using all the Tactical Combat rules. If you ignore weapon reach and facings, then ta map isn't necessary after all.
---
tl;dr No a detailed map isn't a requirement at all. sometimes a sketchy map might be a good idea. Sometimes a map will get in the way of the story.