The land on which Shazhou, Jiangyin County, Jiangsu Province (present-day Zhangjiagang) is located was formed by alluvial deposits of the Yangtze River over a period of thousands of years. As the land grew and changed, local people made paintings of the area, which they petitioned the authorities to acquire. Measurements of the narrow strip of land formed by the river deposits differed, and those seeking to obtain land often conspired with officials, resulting in lawsuits and disorder. Two officials, Wu Heng and Xie Cunbin, together with the magistrate of Jiangyin, finally were given the task of surveying and measuring Shazhou, including the newly purchased territory of Shouxingsha and Laosha. The two men worked diligently, sometimes during rain and snow, to complete their work in five months. These maps contain the results of their survey. They came up with an estimate of 61,200 mu (a Chinese land measure; 1 mu = 613.2 square meters) of newly acquired alluvial land, and 51,000 mu of the lands acquired earlier. They then ranked the land according to different levels of quality and submitted their report to the authorities. In addition, they gradually settled all unresolved land disputes. The surveyors used an ancient bow-shaped wooden device to measure the area following the direction of a magnetic compass. They followed Pei’s six basic principles of cylindrical projection, taking into consideration land position, curves, and other factors. Several inspectors of the survey and two cartographers, Chen Enqing and Huang Fushen, also contributed to the work. The maps produced by the survey are in three sections. The first depicts the newly acquired land, with more than 100 illustrations, bound in two volumes. At the front of the maps is an essay written by Wu Heng on the history of the area. The second part contains eight maps, dealing with the cultivated land, in one volume. The third section deals with the lands of the original acquisition in two volumes, volume one of which has 41 illustrations depicting Changyinsha, Wushansha and Dingtaosha, and volume two of which contains 53 illustrations depicting Shouxingsha (south and north). All these illustrations are executed in an extremely refined style.