Multiscale assessment of land surface phenology from harmonized Landsat 8 and Sentinel-2, PlanetScope, and PhenoCam imagery

• Published in: Remote sensing of environment Vol. 266; no. C; p. 112716
• Main Authors: Moon, Minkyu, Richardson, Andrew D., Friedl, Mark A.
• Format: Journal Article
• Language: English
• Published: New York Elsevier Inc 01.12.2021; Elsevier BV; Elsevier
• Subjects: Algorithms; climate; Climate and vegetation; Data sources; environment; EVI2; Land cover; Land surface phenology; Landsat; Landsat satellites; Monitoring; PhenoCam; Phenology; PlanetScope; Quantiles; Remote sensing; Satellite imagery; Seasonal variations; Sentinel-2; Spatial discrimination; Spatial resolution; Surface properties; Temporal resolution; Terrestrial ecosystems; Time series; time series analysis; variance; Vegetation; Vegetation index; Vegetation indices; PhenoCam; Land surface phenology; Vegetation indices; PlanetScope; Landsat; Sentinel-2; EVI2
• ISSN: 0034-4257; 1879-0704
• DOI: 10.1016/j.rse.2021.112716

As the spatial and temporal resolution of remotely sensed imagery has improved over the last four decades, algorithms for monitoring and mapping seasonal changes in surface properties have evolved rapidly. Most recently, the availability of daily PlanetScope imagery has created new opportunities for monitoring the land surface phenology (LSP) of terrestrial ecosystems at high spatial resolution. However, the quality and value of LSP information from PlanetScope imagery have not been systematically examined. In this paper, we evaluate the character and quality of LSP information derived from PlanetScope by comparing time series of vegetation indices and LSP metrics from PlanetScope to corresponding time series and LSP metrics derived from Harmonized Landsat 8 and Sentinel-2 (HLS) imagery and PhenoCams at six sites that span a diverse range of land cover types and climate. Results show that vegetation index time series from all three data sources show high temporal correlation, and LSP metrics derived from HLS, PlanetScope, and PhenoCam show high agreement with negligible bias. Semi-variograms for phenometrics estimated from PlanetScope imagery indicate that the majority of spatial variance captured in PlanetScope phenometrics occurs well below the spatial resolution HLS imagery. At the same time, LSP metrics from HLS are most strongly correlated with the 50–75% quantiles of 3 m LSP metrics from PlanetScope. This indicates that HLS captures the average phenology at sub-pixel scale captured in PlanetScope imagery. Our results represent the first comprehensive comparison of LSP metrics estimated from PlanetScope and publicly available moderate spatial resolution imagery, and provide insights regarding: (1) the quality and character of LSP metrics derived from HLS and PlanetScope; and (2) the relative merits and trade-offs associated with the use of each data source for LSP studies. •Vegetation index time series from all three data sources show strong agreement.•EVI2 from PlanetScope is lower than EVI2 from HLS due to bias in the red band.•Phenometrics from each source show strong agreement at seasonal time scales.•Phenometrics from each source weaker agreement at sub-seasonal time scales.•Fine-scale variation in LSP is captured by PlanetScope but not by HLS.