His doctoral thesis was Atlas d'Archéologie aérienne de Picardie, 1975; La Somme préromaine et romaine, d'après les prospections aériennes à basse altitude (The Pre-Roman and Roman Somme, Based on Low-Altitude Aerial Prospecting), completed in 1978.
Agache studied Paleolithic and Neolithic and then directed its research toward aerial archaeology in northern France, beginning in 1959.
[4] His early research helped to show that Gallo-Roman agriculture was more extensive and well-developed than had been previously known.
Agache spent several thousand hours in the air, taking and later analysing photographs for evidence of ancient settlement and travel patterns.
[7][8] His thousands of aerial photographs have been placed with the Ministry of Culture, where they may be consulted, for the most part at the DRAC in Picardie.