The fact that a previous survey was being used as a starting point suggests the time-pressure William FitzWilliam Owens was under in the early months of his service to produce results. This is in fact itself a copy (and slight improvement on) an earlier draft of the survey. That erier survey stiil exists but is now beyond repair.
Of further note, and a mark of his diligence and attention to detail, is Owen's comment that 'soundings being taken in different boats are laid down in the same number of colors to avoid confusion'.
William FitzWilliam Owen, from the outset of his servive in the Great Lakes region in May 1815 was initially tasked with a first rapid reconnaissance of the lower lakes and rivers of the region to determine a number of urgently needed facts including the collection of extensive soundings and data. With Britain and America having, just the previous year, been engaged in a war over the territory there was clearly an urgent need for this information.
Owen's work toward this end was not helped by the fact that both he and his crew all suffered from fever and within weeks of setting out on the task. He also struggled with the heated tensions between the British and Americans on the Detroit frontier, which culminated in the arrest and detention of his principal surveying officer at Detroit, Lieutenant Vidal. This of course led to time-consuming negotiations and protracted correspondence between British and American authorities, in order to secure his release.
There are early indications of the artistic construction that Owen put into his later work, which he later passed on to Henry Bayfield almost by way of a 'style': His depiction of the trees and marshland are especially true of this. Owen depicts windmills on the west bank of the river, along with campsites and tents below Amhurstburg, which were presumably used by the survey team. The Forts at Amherstburg and Detroit are both recorded, as is the town of Sandwich.
This beautiful hand-drawn survey and chart of the River Detroit was drawn in 1815 in order to inform British authorities as to the various navigable channels. According to a note by Owens the outline for this survey is copied from 'a Plan in the Engineers Drawing Room at Quebec'.