为定量比较3种地表随机糙率测量方法的异同,采用砾石覆盖、枯落物覆盖及不同农事活动3种下垫面条件,分别利用三维激光扫描法、照相法和测针法测量了不同处理下的地表随机糙率,以激光扫描法测量结果为基准值,通过绝对误差、相对误差和均方根误差比较了3种测量方法的差异。结果 表明:激光扫描法测量精度最高,但仪器价格昂贵,且用于野外测量时需要注意光照影响; 照相法精度较高,测量快捷方便,与扫描法的平均绝对误差为0.65 mm,平均相对误差为14.0%,但需手动测量各控制点间的相对距离,也需要避免光照影响; 测针法易于操作、成本最低,但费时费力、精度不高,与扫描法的平均绝对误差为1.82 mm,平均相对误差为34.1%。因此,3种方法各有利弊,需根据实际情况选择合适的测量方法测定地表随机糙率,当精度要求不是非常严格时,推荐优先使用照相法。研究结果对随机糙率测量方法的正确选择,提高地表糙率测量精度,具有重要的指导意义。
In order to compare the similarities and differences of three measuring methods on surface random roughness quantitatively, 3D laser scanning, photogrammetry, and pin meter methods were used to measure surface random roughness under gravel cover, litter cover and different agricultural activities. The results of 3D laser scanning method were taken as the control, the differences of three methods were compared by absolute error, relative error and root-mean-square error. The results show that the laser scanning method has the highest accuracy, but the scanner is expensive and should be prevented from the influence of sun light when it is utilized in field conditions; photogrammetry has high accuracy and the measurement is efficient and convenient; the mean absolute error and relative error compared with the scanning method are 0.65 mm and 14.0%, respectively, however, the relative distance between the markers should be measured manually and also should be prevented from the influence of sun light; the pin meter method is easy to be operated and has the lowest cost, but it is time-labor consuming, and has the low accuracy, the mean absolute error and relative error compared with the scanning method are 1.82 mm and 34.1%, respectively. All three methods have both advantages and disadvantages. The appropriate method should be selected according to the actual situation to measure surface random roughness. Photogrammetry is recommended if the requirement of accuracy is not very strict. These results are helpful to select a method to measure surface random roughness and to promote its accuracy.
