Evaluating the Impact of Different Spatial Resolutions of UAV Imagery on Mapping Tidal Marsh Vegetation Using Multiple Plots of Different Complexity

Abstract

Highlights: What are the main findings? The classification accuracy of vegetation varied with images at different spatial resolution. Vegetation complexity affected classification accuracy. What are the implications of the main findings? Mapping tidal marshes with different vegetation complexities should use images of different spatial resolutions. UAV data with 5 cm resolution was recommended for tidal marsh vegetation classification in the Yellow River Delta or regions of similar vegetation complexity. Unmanned aerial vehicle (UAV) images have increasingly become important data for accurate mapping of tidal marsh vegetation. They are particularly important for determining what spatial resolution is needed because UAV imaging requires a trade-off between spatial resolution and imaging extent. However, there are still insufficient studies for assessing the effects of spatial resolution on the classification accuracy of tidal marsh vegetation. This study utilized UAV images with spatial resolutions of 2 cm, 5 cm, and 10 cm, respectively, to classify seven tidal marsh plots with different vegetation complexities in the Yellow River Delta (YRD), China, using the object-oriented example-based feature extraction with support vector machine approach and the pixel-based random forest classifier, and compared the differences in vegetation classification accuracy. This study indicated the following: (1) Vegetation classification varied at different spatial resolutions, with a difference of 0.95–8.76% between the highest and lowest classification accuracy for different plots. (2) Vegetation complexity influenced classification accuracy. Classification accuracy was lower when the relative dominance and proportional abundance of P. australis and T. chinensis were higher in the plots. (3) Considering the trade-off between classification accuracy and imaging extent, UAV data with 5 cm spatial resolution were recommended for tidal marsh vegetation classification in the YRD or similar vegetation complexity regions.