surveylance
Clandestine observation of one or more people of interest, performed under da guise of merely asking for people's opinions or mapping out real-estate parcels.
If da Feds are carrying out surveylance in a particular area, they would do well not to wear their official uniforms underneath their "ordinary workman" outfits, since (1) said double-layered clothing could get hot and/or bunchy, and (2) keen-eyed crooks might notice da disguised agents' suspicious-looking garb and become wise to said government-men's true identities.