**3. Results**

### *3.1. Validation of Row Model Using Computer-Simulated Data*

In Figure 6, the distribution of the sum of the reflectance of two models in four scenes (Stage\_rc1, Stage\_rc2, Stage\_rc3, and Stage\_cc) are shown. With an increase in LAI (leaf area index) and a change in row structure (increase in the row width and height, decrease in the between-row distance) (Table 1), the distribution of the sum of the reflectance in the red band and NIR band simulated by the row model and the distribution of the sum of the reflectance in the red band and NIR band simulated by the RGM model have high consistency in four viewing modes (PP mode, OP mode, AR mode, and OR mode). The correlation coe fficients (R) are greater than 0.9281. The root mean square errors (RMSEs) are less than 0.0012 in the red band and less than 0.0095 in the NIR band (Table 4). Moreover, the di fferences between the reflectance simulated by the two models are less than 5%. The consistency of the red band (mean absolute deviation (MAD) = 0.25 × (1.98% + 3.08% + 4.64% + 4.03%) ≈ 3.43%) is greater than that of the near-infrared band (MAD = 0.25 × (1.87% + 2.99% + 1.68% + 1.82%) ≈ 2.08%) (Table 4). With an increase in LAI and a change in row structure, the sum of the reflectance in the red band and NIR band shows opposite trends, i.e., the sum of the reflectance in the red band is decreasing while the sum of the reflectance in the NIR band is gradually increasing. Our model is the same as the RGM model in the inverted v-shaped area where the hotspot is located (PP in Figure 6a,b). When Stage\_rc1 changes to Stage\_cc, the width of hotspots (slope of an inverted v-shaped area) gradually narrows.

**Figure 6.** The distribution of the sum of the reflectance in the red band and near-infrared (NIR) band simulated by the RGM model and the row model in four viewing modes: (**a**) principal plane (PP) mode in the red band, (**b**) principal plane (PP) mode in the NIR band, (**c**) orthogonal plane (OP) mode in the red band, (**d**) orthogonal plane (OP) mode in the NIR band, (**e**) along-row plane (AR) mode in the red band, (**f**) along-row plane (AR) mode in the NIR band, (**g**) orthogonal row plane (OR) mode in the red band, and (**h**) orthogonal row plane (OR) mode in the NIR band. Here, VZA is the viewing zenith angle.


**Table 4.** The statistical results of the comparison of curves of reflectance simulated by the row model versus the reflectance simulated by the Radiosity–Graphics Combined Model (RGM) model.

Figure 7 shows the decomposition of the reflectance in the NIR band in Figure 6b,d,f,h, namely the single-scattering contribution in Figure 7a,c,e,g and multiple-scattering contribution in Figure 7b,d,f,h. In Figure 7a,c,e,g, the overall di fference between the single-scattering contribution in the NIR band simulated by the row model and the single-scattering contribution in the NIR band simulated by the RGM model is small. The R-value is greater than 0.8974 and RMSEs are less than 0.0057 for single scattering in the NIR band in Table 4. Moreover, the di fferences between the single scattering in the NIR band simulated by the two models are less than 3% (Table 4). Figure 8 shows the dense points in the single scattering near the hotspot in PP, with our model and RGM model also having high consistency. In addition to the change in the width of the hotspot, the changing trend of the single-scattering hotspot is more obvious than the sum of the reflectance in Figure 6a,b.

In Figure 7b,d,f,h, the multiple-scattering contribution in the NIR band simulated by our model and multiple-scattering contribution in the NIR band using the RGM model have high consistency. The R-value is greater than 0.7971 and RMSEs are less than 0.0062 for multiple scattering in the NIR band in Table 4. Moreover, the di fferences between the multiple scattering in the NIR band simulated by the two models are less than 10% (Table 4). Comparing Figure 6b,d,f,h and Figure 7b,d,f,h, we can find that the proportion of the multiple scattering in the NIR band in the sum of the reflectance gradually changes from 20% to 50% as LAI increases and changes in row structure (from Stage\_rc1 to Stage\_cc).

Here, R\_NIR\_1 is the single scattering in the NIR band, and R\_NIR\_m is the multiple scattering in the NIR band. R is the correlation coe fficient, RMSE is the root mean square error, and MAD is the absolute value of average di fference, which represents the di fference between Data *A* and Data *B*, expressed as a percentage. Its expression is *m <sup>m</sup>*=1 1 *m* (*<sup>A</sup>* − *B*)/*B* . Here, *m* is the number of comparison groups, *A* is the reflectance simulated by the row model, and *B* is the reflectance simulated by the RGM model.

### *3.2. Validation of Row Model Using In Situ Data*
