## 4 Perspectives and Summary
Moreover, quantitative assessments combined with the parameterized displacement results can be used to simulate the spatial-temporal processes of deformation by virtual reality technologies. These technologies demonstrate spatial-temporal phenomena in accurate and dynamic visual scenarios and can play a critical role in narrowing the communication gap between scientists and end-users responsible for heritage management. In summary, different radar interferometry approaches used in an integrated manner can combine their respective advantages in dealing with diverse heritage sites. According to the characteristics of a specific heritage site and the requirements of end-users, we can also select one or several parts from the proposed workflow to guide monitoring implementation. Based on plenty of systematic investigations over heritage sites with different geological features, environmental conditions and land cover, we can explore the optimum integration of methods and radar observation parameters (e.g., spatial resolution, wavelength, incident angle) dedicated to different scenarios. Then, an application-oriented system can then be set up for anomaly detection and preventive diagnosis of cultural heritage sites. Today, people are much more aware of and focused on culture and civilization issues, which profoundly influence the social and economic development of a nation and its people. The sustainability of cultural heritage is one of our most urgent priorities. On the one hand, cultural heritage management faces conflict of interest between local economic developments and environment conservation, e.g., traveling, deforestation, mining and urban expansion. The proposed workflow can make precise and efficient evaluations of deformation processes and their trends from the site to single monument scale, providing a scientific basis for resource exploitation in and around cultural heritage sites. On the other hand, cultural heritage is also affected by natural factors, particularly natural disasters. Deformation monitoring and preventative diagnosis based on the workflow can contribute to planning appropriate countermeasures for heritage restoration and protection. Furthermore, since the space-borne SAR data are becoming more open to the public, particularly to researchers, limitations regarding cost and ready access of SAR data are likely to be reduced significantly. The establishment and promotion of this system also require a close collaboration amongst archaeologists, radar scientists and cultural heritage managers to improve traditional management approaches. Moreover, by establishing proper communication channels and promoting close cooperation between researchers and end-users, this non-intrusive remote sensing tool could make unique contributions to the sustainability of the cultural heritage of humankind. Figure 1: A workflow model for deformation monitoring and preventive diagnosis that could ultimately lead to the setting up of a differential radar interferometry application system dedicated to cultural heritage site monitoring (within the box enclosed by the dashed line). Ground-based and satellite SAR data can be integrated to retrieve multi-dimensional deformation fields (shown as the dashed line with the arrowhead).