## 1 Introduction  
With the exploitation of coal resources, the problem of coal deposits under buildings, railways and water bodies, namely \"three-under coal deposit issue\", has now arisen in most mining areas [1; 2; 3]. The cropland and building safety in mining area is subject to topography, geomorphology, groundwater level change and other factors. However, regarding the coal-mining-impacted area, the mining-induced surface displacement and deformation mainly account for buildings and cropland damages [4; 5]. In particular, the proportion of coal deposits under villages is prominent [6; 7; 8]. The surface displacement triggered by underground coal mining will not only damage village buildings [9], environments [10], croplands, etc. (as shown in Figure 1), but will also incur enormous compensation against coal enterprises. Therefore, a precise and accurate assessment of the damage level of surface buildings and croplands due to coal mining becomes one of those crucial problems faced by \"three-under coal deposit\" mining. Underground mining impacts surface buildings in multiple respects [11; 12]. Many experts and scholars have carried out in-depth research assessing the coal-mining-induced damages to building and land resources. [PERSON], [PERSON] [13], [PERSON], [PERSON] [14], [PERSON] [15] and [PERSON] et al. [16] analyzed the building failure mechanism through observing the building deformation and damage distribution in coal mining subsidence areas, in combination with numerical simulations and other measures, and then concluded the law on the influence from different displacement indexes upon the structural stability of buildings. According to the analysis by [PERSON] [17] on building damage judgment methods, building classification and computer-aided analysis can facilitate in improving the accuracy of coal-mining-induced damage assessment. [PERSON] [18] judged building damages based on the relationship between the coal mining work face boundary and the building protection boundary through calculating the building protection radius under different geological conditions. Concerning cropland damage, [PERSON], [PERSON] [19] investigated croplands in coal mining subsidence areas in Shandong Province, China, analyzed the status quo, and the trend of cropland damage due to coal mining, and revealed the impacts from cropland damage upon the ecological environment and social stability. [PERSON], [PERSON] [20] researched the law on the influence of coal mining on soil nutrients through numerical simulation and evaluated the possibility of land reclamation under different schemes. [PERSON] [21] and [PERSON] [22] constructed an assessment index system to forecast the coal mining-induced cropland damage and destruction level, and then proposed a compensation scheme based on damage level. Although China has established clear and uniform assessment criteria for both building and cropland damages in coal mining areas, experts and scholars try to introduce GIS technology into the mining damage assessment field [23; 24; 25] due to many factors concerning judgment criteria and the cumbersome damage level judgment procedure. [PERSON] et al. [26] observed the laws on surface subsidence since the initial mining in the Upper Silesia Coal Mine 20 years ago using radar interferometry technology. The map on damage risks in the subsidence area can effectively establish the correlation between underground mining faces and surface buildings [27]. [PERSON] [28] established a GIS risk assessment model to classify the surface building damage areas due to underground coal mining  
Figure 1: The building and cropland damages due to underground coal mining. so as to assess the risks in surface building. Based on the results from the displacement and deformation of the ground surface, [PERSON] [29] designed a visualization system for coal-mining-induced damages to surface buildings by virtue of VB language and in light of GIS, thus achieving a rapid judgment on building damage level.