An accuracy assessment of satellite-derived rangeland fractional cover

Authors: Harrison, Georgia; RIGGE, MATTHEW - Us Geological Survey (USGS); ASSAL, TIMOTHY - Bureau Of Land Management; APPLESTEIN, CARA - Us Geological Survey (USGS); James, Darren; McCord, Sarah

Submitted to: Ecological Indicators
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/18/2025
Publication Date: 2/24/2025
Citation: Harrison, G.R., Rigge, M., Assal, T.J., Applestein, C., James, D.K., McCord, S.E. 2025. An accuracy assessment of satellite-derived rangeland fractional cover. Ecological Indicators. 172:e113267. https://doi.org/10.1016/j.ecolind.2025.113267.
DOI: https://doi.org/10.1016/j.ecolind.2025.113267

Interpretive Summary: Maps of plant cover are an important tool for land managers and researchers. We evaluated the agreement between a map of rangeland vegetation cover (the Rangeland Analysis Platform; RAP) and compared field-measured cover to map predictions. Across the western US, maps had higher error in regions characterized by greater vegetation variability. Further, we observed best agreement between field data and RAP cover maps at the smallest spatial scale considered. We also tested RAP performance in riparian and wetland areas, and observed suitable agreement for bare ground and litter, but not other cover categories. Overall our results can help guide regional applications of RAP cover maps.

Technical Abstract: Satellite-derived maps of vegetation cover provide detailed information about vegetation spatiotemporal patterns and are increasingly used to better understand and manage rangelands. Despite their utility, questions remain regarding the regional and site level accuracy for these maps, especially compared to field-collected data. We conducted an accuracy assessment of the Rangeland Analysis Platform (RAP), using over 17,000 field plots sampled through nationwide rangeland vegetation monitoring programs in the continental U.S. We observed higher overall nationwide map error compared to previous validations of RAP, and absolute error (Mean Absolute Error [MAE] and Root Mean Square Error [RMSE]) was highest for perennial herbaceous and bare ground and lowest for trees (MAE range = 2.98 –10.22 %). There were also differences in map agreement with field data across ecoregions. Generally, map agreement was highest in the Great Basin and lowest in the Great Plains and Desert Southwest. Additionally, we assessed the suitability of using RAP in riparian and wetland areas, which are absent in the current version’s training. Errors for bare ground in riparian areas were lower than errors of upland accuracy assessments (upland MAE = 10.22 %, riparian MAE = 7.22 %), but for all other functional groups, riparian error was higher ('MAE range: 0.21 – 20.49 %). We examine how our results could inform regional applications of fractional cover data while considering error and uncertainty and identify areas for potential model improvement. Our findings inform the use of RAP regionally and provide a technique for evaluating other vegetation mapping products for use in rangeland management.