You have a better chance to get a map if you mine/harvest nodes that don't have a chance to spawn other hiddens in them already, such as Hardsilver Ore and so on.

How do I know this? Use the +30% HQ skill when you get a node that gives +30% HQ chance (which should give you about 75% HQ chance), and if you manage to get 3 HQ items in a row, you can use Luck of the Mountaineer/Pioneer to uncover a map or Grade 5 Carbonized Matter for your last gather attempt. However, you can't use this trick on nodes that already have a hidden revealed, such as the aformentioned Hardsilver Ore.