Satellite observation of coal mining subsidence by persistent scatterer analysis

Ground subsidence persistently occurs in abandoned coal mining areas. This paper presents an investigation of ground subsidence measurement using persistent scatterers recorded by space-borne synthetic aperture radar (SAR). During the period from November 1992 to October 1998, twenty-five JERS-1 SAR interferometric pairs were obtained and used to measure subsidence in the Gaeun coal mining area, Korea. To validate the subsidence estimated by the persistent scatterers SAR interferometry (PS technique), the results were compared with the degree of crack level obtained by a 1997 field survey. The study area was divided into five classes based on measured crack levels. The line-of-sight (LOS) subsidence rate of each group was estimated by the phase of 135 scatterers selected from the five classes. The maximum subsidence was measured by radar as 11.2 cm over 6 yr. The mean subsidence rate of one class was found to be 0.5 cm/yr where cracks most severely developed. The radar-estimated subsidence agrees well with the degree of crack level. The PS technique is useful for the measurement of ground subsidence in abandoned coal mining areas, even in mountainous regions.