It had only been a couple of hours and the two of them managed to map out the landscape from the railway tracks to the west and 50 miles to the east of the tracks. It was not that long of a distance if a ranker was just running or walking it, but the amount of detail that they got on the map is what made it impressive.
When they were mapping out the area around where they were living with Havok, it was much easier because he used his 'Hidden Presence' on them. Which greatly reduced the chance that they would be spotted. They obviously didn't have that. They were on their own. It was dangerous to watch a group or individual because almost everyone did not like to be disturbed or have others sell or spread the information about where they lived.
Even for the areas like the ones that Havok just mentioned, those were dangerous even if there was no one living in them.