The Tidal Wave attack was briefed for 250 feet at 200 mph for the simple bombsight fitted in the aircraft for the raid to work. Much of the ingress/egress was flown at around 500 feet in an attempt to avoid radar detection.
I remember reading the account of one pilot flying in China. May have been one of the "over the hump" flights. His planned altitude was suppose to keep him several thousand feet over the terrain below. He was flying through clouds a good part of the way and they cleared up at one point. He was thinking how pretty the country side was when he realized he could make out individual leaves on the trees .... Decided he was not flying high enough. I think it was due to lack of knowledge or detail there of in the local topography. Could have been that he was a bit off course as well though.
Some really low flying Japanese planes are pictured in the thread at: Famous photo G4M Rikkos Skimming the Water at Guadalcanal 1942
The second one. When you are flying on instruments, knowledge of local terrain goes right out the window. The weather and winds were very treacherous at times, and aircraft were blown off course by hundreds of miles(they were flying IFR of course). Carl Constein, a local copilot who flew the Hump many times, talked about making a flight course correction of 30 degrees - almost unheard of to make such a large correction, but it shows how strongly the winds were pushing the C-46 off course that day.
The article I read suggested it was the topological maps but thinking back to some of the stories my uncle told (he taught navigation to USAAF navigators and served a tour with 8th AF) the latter possibility popped into my mind.
Not having the geographical knowledge about the area terrain is one of the main factors pilot fly low.
