Thakbast Surveys were conducted in 1845-1877 for demarcating the mouza (also loosely called village) boundaries and ascertaining the rural resources of Bengal. Thak is a Persian word meaning boundary pillar. Bengal mouzas had no precise legal boundaries until this survey. Mouza boundaries were hitherto defined nationally in terms of natural marks like nalas or creeks, ancient trees, rivers, marshes, jungles, roads, other mouzas and so on. Such a system worked well in the past when population was scarce and the man-land ratio was in favour of man. But in the late 19th century, when pressure on land increased significantly, such a system became productive of frequent boundary disputes and litigation. Besides, hitherto, rents were assessed on the basis of custom and past records only. Never was any survey made for ascertaining the actual resources of estates. Getting to know the village resources more accurately on the part of the colonial state was, therefore, a necessity both from administrative and revenue considerations.

The success of the Thakbast surveys in the Northwestern Provinces had inspired the authorities to undertake them in Bengal districts also. The operation was begun in 1845 and completed in 1877. The object of the operations was to demarcate mouza boundaries, estate boundaries within the mouza, assess landed and other resources, identify various types of landed interests, chart out geographical and topographical features by scientific mapping of all mouzas, parganas and districts. A mouza was the unit of the Thak survey. A sketch map, in some districts scaled, was compiled for every village showing the estates, households, fields, crops grown, population and physical features. Every village was given a Thak number as a reference. Based on the findings of Thak surveys revenue surveys were conducted subsequently. [Sirajul Islam]