| 摘要 |
Apparatus and method for performing surveillance of an area (4), comprising: placing an amount of material (8) within a portion of the area (4), the material (8) being a granular material having a grain size of less than 65 mm diameter, the material (8) being material that, to some extent, reflects or emits electromagnetic radiation, wherein reflected electromagnetic radiation has a wavelength that is not within the visible light wavelength range; thereafter, imaging, using a sensor (14) configured to detect the reflected or emitted electromagnetic radiation, the area (4), thereby providing one or more images of the area (4) and the material (8) placed therein, and analysing the images to detect a disturbance of the placed material (8). |
