Signal flags... I wouldnt want to be up on a platform or signal tower trying to maintain control of a 6x6 much less a 10-12 footer in a brisk wind...
Behind the house where I grew up south of Richmond was indicated on many period maps had a CS signal tower on the river.. they relayed data up and down the river via same... Saw period photo of one of them further down the line after the Feds took the area, they were constructed quite large and very tall... quite an engineering feat just using rough sawd logs. We never did figure out exacty where it was, nor any excavated evidence..
Frederick