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空-谱增强与半监督协同的小样本地块级林果识别

Parcel-based orchard recognition using a semi-supervised spatial-spectrum enhancement network under small samples

  • 摘要: 针对传统深度学习方法在小样本下县域尺度的地块级林果种植分布提取精度不高的问题,该研究提出了一种基于空-谱语义特征增强与动态样本扩展的可泛化的地块级林果作物智能识别方法。首先,基于GF-2等高空间分辨率遥感影像,选取迁移学习参数优化的BsiNet耕地地块分割网络获取耕地地块数据集,并与Sentinel-2A多光谱影像进行空间位置映射,获取各个地块的影像多光谱数据。其次,构建了一种空-谱语义特征增强的轻量化深度可分离卷积残差网络(LiteTransResNet),增强网络对空-谱语义信息这类深层次特征的表达;进而,引入半监督学习策略实现样本标签的动态扩展,减少模型参数训练所需的样本数量,同时提升模型对跨空间域林果作物识别任务的泛化性;最后,设计了一种集成BsiNet分割网络与半监督学习LiteTransResNet模型的地块级林果作物分类识别方法,实现小样本下县域地块级林果种植空间分布制图。以新疆伽师县西梅林果为例,实地外业调查数据与当地农业部门提供的种植面积数据为参考基准对该模型进行了验证。结果表明,在巴仁镇和米夏乡两个区域,该研究提出的半监督学习的LiteTransResNet模型在小样本条件下林果分类准确率达到99.11%和99.46%,显著优于同类方法。进一步利用巴仁镇与米夏乡的西梅样本数据训练,该模型在全县12个乡镇西梅种植面积的估算误差范围在2%~9%,验证了该模型仅利用2个乡镇的小样本数据集可实现全县林果地块级的高精度识别并具有良好的泛化性能。该研究可为大范围林果作物类型调查与监测提供高精度的 1 m 分辨率的耕地地块数据,以及10 m分辨率的林果作物空间分布信息。

     

    Abstract: A generalized intelligent recognition framework was developed for county-scale, parcel-level orchard mapping to address the limitations of conventional deep learning approaches under small-sample conditions, particularly the difficulty of achieving high accuracy in spatially heterogeneous agricultural landscapes. Farmland parcels were initially delineated using a Boundary-Enhanced Segmentation Network (BsiNet) optimized through transfer learning on high-resolution GF-2 imagery, which enabled precise identification of parcel boundaries despite variations in shape, size, and background complexity. The resulting parcels were then spatially aligned with Sentinel-2A multispectral imagery to extract comprehensive spectral information, including multiple visible, near-infrared, and shortwave-infrared bands, for each parcel. This combination produced a high-quality parcel-level dataset integrating precise spatial geometry with rich spectral features, providing a solid foundation for subsequent classification and analysis. To enhance the extraction and fusion of deep spatial–spectral semantic features, a lightweight depthwise separable convolutional residual network, termed LiteTransResNet, was designed. The network incorporated multi-level spatial–spectral feature enhancement modules, residual connections, and depthwise separable convolution operations to improve representational capacity, enabling the model to capture both local spatial structures and subtle spectral variations while maintaining computational efficiency suitable for large-scale agricultural applications. To overcome the limitations of scarce labeled data, a semi-supervised learning strategy was employed to dynamically expand the labeled dataset by selecting high-confidence predictions from unlabeled parcels. This approach reduced the dependency on manual annotation and significantly enhanced the generalization capability of the model for cross-regional orchard classification tasks. The integrated framework, combining BsiNet-based parcel delineation with semi-supervised LiteTransResNet classification, was applied to plum orchards in Jiashi County, Xinjiang, China, and validated using field survey records and planting area statistics provided by local agricultural authorities. In Baren and Mixia townships, the proposed method achieved overall classification accuracies of 99.11% and 99.46%, respectively, substantially outperforming conventional deep learning methods and demonstrating the effectiveness of combining spatial–spectral semantic feature enhancement with semi-supervised learning under limited sample conditions. Furthermore, when trained using only plum samples from these two townships, the model estimated plum planting areas across twelve townships of Jiashi County with errors ranging from 2% to 9%, highlighting its robust generalization capability despite minimal training data. The framework also generated high-resolution farmland parcel data at 1-meter spatial resolution and orchard distribution maps at 10-meter resolution, effectively capturing both local spatial patterns and multispectral characteristics, which facilitated accurate county-scale orchard mapping and provided reliable inputs for precision agricultural management. The results indicated that integrating spatial–spectral semantic feature enhancement with semi-supervised learning substantially improved classification performance under small-sample conditions, while the lightweight network structure ensured efficiency and scalability for extensive mapping tasks. Overall, the study presented a reliable approach for high-precision, parcel-level orchard recognition and spatial mapping under constrained sample availability, confirming that county-wide orchard distributions could be accurately estimated using minimal labeled data. The methodology provided strong support for regional-scale orchard monitoring, crop type mapping, growth assessment, yield estimation, and precision agriculture applications. Additionally, the framework offered a transferable solution for other high-resolution, small-sample agricultural remote sensing tasks, demonstrating the potential of combining advanced deep learning architectures with semi-supervised learning strategies to achieve robust generalization and scalable performance across heterogeneous landscapes. These findings underscored the value of integrating high-resolution spatial information, multispectral features, and adaptive training strategies to enhance both the accuracy and operational efficiency of large-scale orchard classification and monitoring, providing a practical and replicable reference for future precision agriculture research and implementation.

     

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