There was a time, not so long ago, when people had to read paper maps to figure out where to go, rather than let the map tell them what to do. Don't worry, we're not going to get all nostalgic on you. Even if you could read a map, you couldn't do it while driving, requiring frequent stops. And refolding a map is an impossible, thankless task. Simply. The. Worst.
But seeing as Close Encounters was made in that dark time of human existence, physical maps will at least provide us with some interesting imagery to go along with the headache.
Maps pop up in the film whenever someone's trying to find their way. "Lost" here means not knowing what to do as much as meaning not knowing where to go. Maps help the characters find their way in the physical and metaphorical sense: finding one's way—making choices, knowing your direction and purpose in life.
Roy pulls out his maps when he's lost and trying to find his way to Tolono to fix the power outage. After his encounter with the UFO, he becomes lost again, but this time he's lost in his understanding of the world; he can't find a way to explain what he experienced. As he tells his family during dinner:
ROY: I can't describe it, what I'm feeling. What I'm thinking. This means something. It's important.
Just as he couldn't find his way on the map, he can't find his way to understanding what he saw or why it's important.
Maps also help Lacombe and his team find the mystery confronting them. After transmitting the five-tonal phrase into space, his research team begins to receive seemingly random numbers in response. Looking at the numbers, Laughlin has an epiphany:
LAUGHLIN: Excuse me. Excuse me. Before I got paid to speak French, I used to read maps. This first number is a longitude. Yeah. Two sets of three numbers: degrees, minutes and seconds. And the first number has three digits and the last two are below 60. Obviously, it's not in the right ascension and declination on the sky. These have to be Earth coordinates.
Using a globe they find in the director's office, the team determines that the signal is pointing them toward somewhere in Wyoming. They've found their way.
And it's ultimately a map that helps Roy find his way. As it turns out, the mountain image the aliens were beaming into his head was a map, directing him and the other chosen few to the alien encounter. We see the image's proto-Google Maps quality in the following exchange:
JILLIAN: There's a ravine, it leads straight up. There's an easier climb. It faces northeast.
ROY: It's no good. When you get to the top, it's a 300-foot drop straight down. Get down!
LARRY: What's it like on the other side?
ROY: It's a box canyon on the other side with ravines and trails. Take this gradual incline to the right.
JILLIAN: I never imaged that. In my painting I only painted one side.
LARRY: There was no canyon in the doodles I made.
ROY: Next time, try sculpturing.
The aliens were providing directions to their earth-side shindig the whole time. Although, to save everyone the headache next time, Roy should really teach them the wonders of an RSVP card.
Thanks to the telepathic Devils Tower map, Roy, who's lost for most of the film, discovers the truth of his experiences. Lacombe, too, was lost in his quest to find the cause of the mysterious phenomena popping up all over the world. With the help of maps and his cartographer/translator, he also finds his way to an answer: We are not alone.