Passage: Archaeological research on the Eifel aqueduct started in the 19th century. C.A. Eick was the discoverer of the farthest source from Cologne at Grüner Pütz near Nettersheim (in 1867). Systematic study of the aqueduct was carried out from 1940 to 1970 by Waldemar Haberey (de). His 1971 book is still a suitable guide along the course of the construction. In 1980, archaeologist Klaus Grewe (de) completely mapped out the location line and added it to the official German topographic map. His Atlas der römischen Wasserleitungen nach Köln (Atlas of Roman Aqueducts to Cologne, 1986) is a standard work for researchers in Roman architecture.

Question: what year did the archaeologist map out the location?
1980