Optimization of Scanning Scheme for Low-height Vegetation Survey Based on Terrestrial Laser Scanning - A Case Study on the Restored Sand Land, Southern Qinghai-Tibetan Plateau

Abstract Background: In recent decades, vegetation surveys based on terrestrial laser scanning (TLS) have developed rapidly, especially on the forest inventory, but few studies have been conducted to the low-height vegetation. Because of the high investigation cost and subjectivity, it is impending to provide a scientific scanning scheme based on the TLS for the low-height vegetation survey (e.g. shrub, grassland, and meadow) in eco-fragile region (e.g. Qinghai-Tibetan Plateau). Method: In this study, we extracted the vegetation parameter i.e., number, height (H), and crown width (CW) of the two sample plots to evaluate the integrity of the data collected by TLS, on the restored sand land in southern Qinghai-Tibetan Plateau. We assessed the difference between the scanning mode of single-scan (SS) and multiple-scan (MS), and evaluated the influence of terrain fluctuation (windward slope, leeward slope, and the peak of slope) on the determination of scanning spots.Results: The results showed that: (1) the accuracy of vegetation parameter extracted by the mode of SS was mainly affected by the occlusion and the distance from central scanning spot, the RMSE of vegetation parameters is the smallest (RMSEH = 0.186 m; RMSECW = 0.208 m) within 20 m from the central scanning spot. (2) For the MS mode, in addition to the central scanning spot, the scanning spot located at the peak of the slope is the most important, which was the connection of combining the data of windward slope and leeward slope.Conclusion: To sum up, the scientific layout of scanning spot is the key to collecting data by TLS efficiently, and topography is the main factor affecting the layout of scanning spot. Since occlusion effect cannot be avoided, it can only be compensated by setting up more scanning points. Secondly, the accuracy of different sensors will has influence on the distance between adjacent scanning spots.