The 1840–41 Royal Engineers maps of Palestine, Lebanon and Syria was an early scientific mapping of Palestine (including a detailed mapping of Jerusalem), Lebanon and Syria.
It represented the second modern, triangulation-based attempt at surveying Palestine, following the French "Carte de l'Égypte".
It has occasionally been mislabeled as an Ordnance Survey map; in fact none of the officers worked for the Ordnance Survey, which was a separate organization. The Ordnance Survey of Jerusalem, carried out almost 25 years later, was a separate and materially more detailed endeavor.
Jerusalem map.
The Jerusalem map was printed privately for the Board of Ordnance in August 1841. It was published in a reduced form in Alderson's ‘’Professional Papers of the Royal Engineers’’ in 1845, and subsequently as a supplement to the 1849 second edition of Reverend George Williams' "The Holy City: Historical, Topographical, and Antiquarian Notices of Jerusalem" together with a 130-page memoir on the plan. The memoir contained a three-page appendix defending the plan from criticism received from Edward Robinson.
The map may have been the source of the modern tradition of dividing Jerusalem into four "quarters". Matthew Teller writes that this convention may have originated in the 1841 map, or at least George Williams' subsequent labelling of it.
Regional maps.
The regional maps were never published in their entirety. A private printing for the British Foreign Office was produced in 1846. The only published map, Map 2, was published in Charles Henry Churchill's book on Mount Lebanon. Map 3 was used in the creation of Van de Velde's map.
Charles Wilson later explained that the data "was in too fragmentary a state for publication". 
Criticism.
The survey contained a number of flaws. The theodolite was often operated by Symonds alone, miscalculations were made around heights (e.g. on the Sea of Galilee), and the outlines of the Haram es-Sharif in Jerusalem were known to have been miscalculated. As such, scholars such as Edward Robinson and August Petermann chose not to trust the work.
References.
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