Evaluation of the Simard et al. 2011 Global Canopy Height Map in Boreal Forests
Light detection and ranging (LiDAR) provides a state-of-the-art technique for measuring forest canopy height. Nevertheless, it may miss some forests due to its spatial separation of individual spots. A number of efforts have been made to overcome the limitation of global LiDAR datasets to generate w...
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| Format: | Article |
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MDPI AG
2020-03-01
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| Series: | Remote Sensing |
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| Online Access: | https://www.mdpi.com/2072-4292/12/7/1114 |
| _version_ | 1797571844959633408 |
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| author | Wei Yang Akihiko Kondoh |
| author_facet | Wei Yang Akihiko Kondoh |
| author_sort | Wei Yang |
| collection | DOAJ |
| description | Light detection and ranging (LiDAR) provides a state-of-the-art technique for measuring forest canopy height. Nevertheless, it may miss some forests due to its spatial separation of individual spots. A number of efforts have been made to overcome the limitation of global LiDAR datasets to generate wall-to-wall canopy height products, among which a global satellite product produced by Simard et al. (2011) (henceforth, the Simard-map) has been the most widely applied. However, the accuracy of the Simard-map is uncertain in boreal forests, which play important roles in the terrestrial carbon cycle and are encountering more extensive climate changes than the global average. In this letter, we evaluated the Simard-map in boreal forests through a literature review of field canopy height. Our comparison shows that the Simard-map yielded a significant correlation with the field canopy height (R<sup>2</sup> = 0.68 and <i>p</i> < 0.001). However, remarkable biases were observed with the root mean square error (RMSE), regression slope, and intercept of 6.88 m, 0.448, and 10.429, respectively. Interestingly, we found that the evaluation results showed an identical trend with a validation of moderate-resolution imaging spectroradiometer (MODIS) tree-cover product (MOD44B) in boreal forests, which was used as a crucial input data set for generating the Simard-map. That is, both the Simard-map and MOD44B yielded an overestimation (underestimation) in the lower (upper) tails of the scatterplots between the field and satellite data sets. This indicates that the MOD44B product is the likely source of error for the estimation biases of the Simard-map. Finally, a field calibration was performed to improve the Simard-map in boreal forests by compensating for the estimation biases and discarding non-forest areas, which provided a more reliable canopy height product for future applications. |
| first_indexed | 2024-03-10T20:47:24Z |
| format | Article |
| id | doaj.art-f50ba5224b2243cebafdb8eb4753e04c |
| institution | Directory Open Access Journal |
| issn | 2072-4292 |
| language | English |
| last_indexed | 2024-03-10T20:47:24Z |
| publishDate | 2020-03-01 |
| publisher | MDPI AG |
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| series | Remote Sensing |
| spelling | doaj.art-f50ba5224b2243cebafdb8eb4753e04c2023-11-19T20:16:39ZengMDPI AGRemote Sensing2072-42922020-03-01127111410.3390/rs12071114Evaluation of the Simard et al. 2011 Global Canopy Height Map in Boreal ForestsWei Yang0Akihiko Kondoh1Center for Environmental Remote Sensing, Chiba University, Chiba 263-8522, JapanCenter for Environmental Remote Sensing, Chiba University, Chiba 263-8522, JapanLight detection and ranging (LiDAR) provides a state-of-the-art technique for measuring forest canopy height. Nevertheless, it may miss some forests due to its spatial separation of individual spots. A number of efforts have been made to overcome the limitation of global LiDAR datasets to generate wall-to-wall canopy height products, among which a global satellite product produced by Simard et al. (2011) (henceforth, the Simard-map) has been the most widely applied. However, the accuracy of the Simard-map is uncertain in boreal forests, which play important roles in the terrestrial carbon cycle and are encountering more extensive climate changes than the global average. In this letter, we evaluated the Simard-map in boreal forests through a literature review of field canopy height. Our comparison shows that the Simard-map yielded a significant correlation with the field canopy height (R<sup>2</sup> = 0.68 and <i>p</i> < 0.001). However, remarkable biases were observed with the root mean square error (RMSE), regression slope, and intercept of 6.88 m, 0.448, and 10.429, respectively. Interestingly, we found that the evaluation results showed an identical trend with a validation of moderate-resolution imaging spectroradiometer (MODIS) tree-cover product (MOD44B) in boreal forests, which was used as a crucial input data set for generating the Simard-map. That is, both the Simard-map and MOD44B yielded an overestimation (underestimation) in the lower (upper) tails of the scatterplots between the field and satellite data sets. This indicates that the MOD44B product is the likely source of error for the estimation biases of the Simard-map. Finally, a field calibration was performed to improve the Simard-map in boreal forests by compensating for the estimation biases and discarding non-forest areas, which provided a more reliable canopy height product for future applications.https://www.mdpi.com/2072-4292/12/7/1114LiDARtree heighttree coverboreal forestsremote sensing |
| spellingShingle | Wei Yang Akihiko Kondoh Evaluation of the Simard et al. 2011 Global Canopy Height Map in Boreal Forests Remote Sensing LiDAR tree height tree cover boreal forests remote sensing |
| title | Evaluation of the Simard et al. 2011 Global Canopy Height Map in Boreal Forests |
| title_full | Evaluation of the Simard et al. 2011 Global Canopy Height Map in Boreal Forests |
| title_fullStr | Evaluation of the Simard et al. 2011 Global Canopy Height Map in Boreal Forests |
| title_full_unstemmed | Evaluation of the Simard et al. 2011 Global Canopy Height Map in Boreal Forests |
| title_short | Evaluation of the Simard et al. 2011 Global Canopy Height Map in Boreal Forests |
| title_sort | evaluation of the simard et al 2011 global canopy height map in boreal forests |
| topic | LiDAR tree height tree cover boreal forests remote sensing |
| url | https://www.mdpi.com/2072-4292/12/7/1114 |
| work_keys_str_mv | AT weiyang evaluationofthesimardetal2011globalcanopyheightmapinborealforests AT akihikokondoh evaluationofthesimardetal2011globalcanopyheightmapinborealforests |