How does a spy or scout move through a territory unobserved by anyone else while successfully observing and reporting back on all human movements in that area? Presumably Poul Anderson's Dominic Flandry possesses such skills to be used if he is down on a planetary surface without any access to high tech surveillance equipment? No doubt Anderson's canon includes accounts of scouts? The Time Patrol deploys minute spying gadgets: self-directing, full-sensory-input-collecting recorders operating on the molecular level.
When SM Stirling's Rudi Mackenzie recommends his twin half-sisters as scouts, he demonstrates their skills and surprises his colleague by suddenly asking the sisters to emerge from their nearby unlikely hiding places. When an SAS type in a Frederick Forsyth novel suspected that a dead letter drop had been compromised, he hid and watched it, all senses alert, for eight hours, a day's work. Only then was he certain that enemy troops were not also watching the drop from concealment. But how could he always be sure of finding, in any terrain, somewhere to conceal himself while retaining his ability to observe his total surroundings? It beats me.