ENDBSI: an Enhanced Normalized Difference Bare Soil Index for identifying the bare soil of urban and rural regions in China

Bare soil is an important indicator for evaluating urbanisation and is essential for research on sustainable development. Traditional bare soil indices have limited applicability across different geographic regions and soil types and are sensitive to interference from impervious surfaces. Consequently, few indices are widely adopted for bare soil identification in both urban and rural environments. In this study, a new index, called the Enhanced Normalized Difference Bare Soil Index (ENDBSI), is developed by integrating the spectral characteristics of various land cover types across multiple study areas. The results show that the proposed index enables accurate bare soil extraction in both urban and rural environments. By validating the ENDBSI across 14 study areas in China, each dominated by a different soil type and consisting of urban and rural areas, the index is shown to consistently outperform existing bare soil indices for bare soil identification, namely, the Bare Soil Index (BSI), Normalized Difference Bare Soil Index (NDBSI), and Product Index for Dark Soil (PIDS). Moreover, it achieves a greater spectral contrast between bare soil and impervious surfaces, improving the accuracy of bare soil mapping. The ENDBSI demonstrates excellent performance in bare soil identification across all 14 study areas, with an average spectral discrimination index between bare soil and non-bare soil exceeding 2.41 and an average identification accuracy of 94.33%. The results highlight the index’s strong applicability and transferability across diverse environments. These findings suggest that the ENDBSI is suitable for the large-scale remote sensing monitoring of bare soil and has the potential to significantly improve bare soil observation and mapping across China.