I am not familiar with the Confederate positions being referred to as outposts- although I know there was one by that name in western Arlington County near Seven Coners. It would have been in line with the Confederate held position at Munson’s Hill in Falls Church on the Leesburg Turnpike (State Route 7).
Do have a list of Outposts by their number?
The best I can tell you right now that before the Confederate Army withdrew to Centreville in October 1861, their line extended from Fairfax Court House north to Chantilly and Herndon. JEB Stuart’s cavalry camped on Ox Road in Fairfax near the site of the present Fire Training Academy. There was also a redoubt built by the 5th Alabama Regiment at Farr’s Crossroads- Braddock Road & Ox Road at George Mason University.
There was a Benjamin Franklin Cockerill who was born in Herndon in 1850- too young to be the landowner at the time, but was maybe the son. Also the Cockerill name may have been attached to the map after the war. The name is also spelled Cockrill in the records, among some of the variations. The family lived in Herndon up through the 20th century.