Abstract: Historical grid data of land use are the basis for environmental effect simulation of land use/land cover change. This study distributed the cropland data for the mid-Qing Dynasty in Jiangsu and Anhui Provinces into grid cells with a spatial resolution of 10 km×10 km by using the provincial-level and county-level cropland data. It also compared and assessed the two distribution results to examine the accuracy of the downscaling and rasterization of statistical data at different spatial scales. The results are as follows: (1) The distribution result that used the county-level data has higher precision. (2) There exist differences between the provincial and county statistical data downscaling results, and the average difference is 16.61%. For 24.55% of the grid cells the difference is between -10% to 10%; 13.3% of the grid cells have a difference of above 70% or below -70% and these cells are mainly in the Hongze Lake basin and the northern plain of Jiangsu Province (the estuary before the Yellow River diversion). To reduce the distribution error and improve the downscaling precision, it is necessary to reconstruct historical cropland distribution using county data. (3) The reconstructed cropland distribution in the mid-Qing Dynasty in Jiangsu and Anhui Provinces reveals some regional differences. The highly farmed area was mainly concentrated in Taicang and Kunshan in the central eastern coastal plain region, and in Dangshan, Feng, and Pei Counties the reclamation rates were above 80%, with the highest in Dangshan at 89.8%. But the reclamation rate in the estuary of the old Yellow River course in the north of Jiangsu, the Hongze Lake basin, the Tai Lake basin, and the southern Anhui mountainous and hilly region was very low, at around 10%. (4) In terms of altitude and slope, in 1735, the cropland was mainly distributed in places where the altitude is lower than 100 m and slope lower than 2°. In the 1980s, however, the reclamation rate had greatly increased in areas with various slopes—for example, the reclamation rate under 2° slope increased from 45.29% in 1735 to 74.21% in the 1980s.

Key words: accuracy comparison, Jiangsu and Anhui Provinces, Land use, rasterization, the Mid-Qing Dynasty