## 3 Results
### DEMs Evaluation  
CRDTM2020 and nine global DEMs were evaluated over the study area using elevations from LVIS surveys and the levelling dataset. The differences computed as \(H_{\text{diff}}=H_{\text{LVIS}}-H_{\text{DEM}}\) are listed in Table 4 for both validation datasets. Large outliers of hundreds of metres can be observed. The large positive outliers are linked to cloud borders, which is not unexpected and mentioned in the L2 LVIS product description. However, the large negative values correspond to errors in either DEMs or LVIS data. Figure 15 are the histograms of the \(H_{\text{diff}}\) between ten DEMs and three LVIS surveys. Similarly, Figure S3 for the levelling dataset can be found in Supplementary S4. As there are few validation points and few vegetation effects, those histograms indicate an almost normal distribution. The majority of LVIS data were collected over vegetated areas, and therefore, in Figure 15, the histograms for DSMs, NASADEM, SRTMs, TanDEM-X, ASTER, and AW3D30 are skewed and appear as the sum of two distributions: one representing uncertainties over vegetated areas (short and wide bell curve) and one for uncertainties in bare-earth areas (tall and narrow bell curve). Each LVIS point provides values of highest return ZT, allowing the separation of each dataset into points above vegetated areas (ZT \(>\) 0) and bare-earth areas (ZT = 0). For the separation of the levelling dataset, we used canopy density values interpolated to the point locations using nearest neighbour interpolation. The results are presented in Table 5. The percentages of bare-earth points for LVIS2019, LVIS2005, LVIS1998, and levelling are 31.6%, 16.4%, 0.3%, and 54.4%, respectively. CRDTM2020 and the MERIT DEM are bare-earth DTMs and have a distinctive single peak in the histograms in Figure 15. The differences follow a nearly normal distribution with an additional spike. However, for the BEST DEM DTM, the spike is not in the centre of the histogram. When evaluating it with LVIS datatsets, we concluded that the cells above vegetated areas were provided in terms of ellipsoidal heights, while the bare-earth cells were provided as physical heights. The histogram in Figure 15c was computed by subtracting EGM96 geoid heights from the BEST DEM. Observe that the second pronounced peak corresponding to bare-earth cells in this case is centred at about \(-12\,\mathrm{m}\). If the heights of the BEST DEM were used as they were, histograms had a large shift (ME of 7.3 m) to the right of the bell-shaped distribution for vegetated areas, while the spike was very close to zero. The histograms for the validation of DEMs with the levelling dataset provided in  
Figure 14: Histogram of the differences between NASADEM (first row) and CRDTM2020 (second row) from three LVIS surveys from 2019, 2005, and 1998. Note that the LVIS2005 dataset was used for the determination of coefficient \(a\) in the vegetation bias correction model, while the LVIS2019 and the LVIS1998 datasets were used only for validation. The statistics is provided in terms of the Median Difference (MED), Median Absolute Difference (MAD), mean difference, and Standard Deviation (STD\({}^{\bullet}\)) for differences without outliers larger than \(\pm 50\,\mathrm{m}\). Supplementary S4 offer both histograms and statistics for the BEST DEM, with and without the transformation of the ellipsoidal heights to physical heights.