<p>Accurate classification of cropland and crop types is essential for agricultural management in arid irrigation districts but remains challenging due to spectral similarity among crops and interference from heterogeneous non-cropland backgrounds. To address these challenges, this study develops a hierarchical framework for cropland and crop-type mapping using Sentinel-2 time-series data on the Google Earth Engine platform. A two-stage strategy is adopted, in which cropland is first delineated using a support vector machine with a radial basis function kernel (SVM<sub>RBF</sub>) based on multi-temporal spectral features and indices, followed by crop classification within the cropland mask using a random forest (RF) model incorporating phenology-driven temporal features. Using Sentinel-2 imagery (10&#xa0;m resolution) and ground-truth samples from the Qingtongxia Irrigation District, the proposed approach achieves an overall accuracy of 94.61% for cropland classification. The overestimation of cropland area is reduced to 9.7%, compared with 17–19% in existing high-resolution land-cover products. For major crops such as maize and rice, classification accuracies exceed 86%, representing an improvement of 5–10% over single-stage classification approaches. This study also provides a systematic comparison between the derived cropland map and existing high-resolution land-cover products, highlighting the challenges that such products may encounter when applied to heterogeneous irrigation-district environments. Overall, this study provides an interpretable and practical framework for improving crop mapping in complex irrigation environments.</p>

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A hierarchical framework for cropland and crop classification in the Qingtongxia irrigation district using support vector machine and random forest models

  • Xiaoqian Xu,
  • Wen Wang,
  • Houjun He,
  • Xiaoqiang Zhang

摘要

Accurate classification of cropland and crop types is essential for agricultural management in arid irrigation districts but remains challenging due to spectral similarity among crops and interference from heterogeneous non-cropland backgrounds. To address these challenges, this study develops a hierarchical framework for cropland and crop-type mapping using Sentinel-2 time-series data on the Google Earth Engine platform. A two-stage strategy is adopted, in which cropland is first delineated using a support vector machine with a radial basis function kernel (SVMRBF) based on multi-temporal spectral features and indices, followed by crop classification within the cropland mask using a random forest (RF) model incorporating phenology-driven temporal features. Using Sentinel-2 imagery (10 m resolution) and ground-truth samples from the Qingtongxia Irrigation District, the proposed approach achieves an overall accuracy of 94.61% for cropland classification. The overestimation of cropland area is reduced to 9.7%, compared with 17–19% in existing high-resolution land-cover products. For major crops such as maize and rice, classification accuracies exceed 86%, representing an improvement of 5–10% over single-stage classification approaches. This study also provides a systematic comparison between the derived cropland map and existing high-resolution land-cover products, highlighting the challenges that such products may encounter when applied to heterogeneous irrigation-district environments. Overall, this study provides an interpretable and practical framework for improving crop mapping in complex irrigation environments.