This is a comprehensive treatment of the subject by Dick Tennant looking at the cartography of French, Portuguese and British cartographers.   Maps in the Peninsular War   

IGN have released a new map of Verdun and updated an existing edition to commemorate the 100th Anniversary of the Battle of Verdun. Forêts de Verdun et du Mort-Homme Is a walking map of the forests around Verdun at 1:25000 scale Grande Guerre - Bataille de Verdun 1916 Is a new map of