Crashlands Map System

[doombrowski]

I am creating a smaller open world game in GMS2 that would greatly benefit from a mapping system which reveals portions of the map as you explore. I have managed to create maps using a pathfinding grid but have yet to figure out a way to gradually reveal portions of this map as players explore. I was wondering if any of the BScotch fellas could key me in on the method that was used in Crashlands to create the map reveal effect or perhaps the way that it would be done if it were to be implemented now as opposed to a couple years ago. I understand that you're all very busy so if you can't or don't want to answer, no biggie.