Series Number Id: GSGS 3274. Sheet number: part of sheet 28. Black base map, photographically reproduced from the French 1:80,000 map sheets of the Somme area. Shows "original line" and lines on July 7th, 14th, 21st, and 31st, as well as "approximate lines" (shown pecked); British lines are in red overprint and French lines in blue overprint. Covers the whole area of the Somme battlefield, including Albert, Bapaume and Péronne, from Hebuterne in the north to Rouvroy-en-Santerre in the south, and from Bouzincourt in the west to Fins in the east., Location: Research Collections; Fonds: WW1 Trench Maps: France; Box number: PC20; envelope_number: 629.