Assessing the Interest of a Multi-Modal Gap-Filling Strategy for Monitoring Changes in Grassland Parcels

Abstract

One key factor to exhaustive vegetation monitoring lies in the dense temporal sampling of the measurements. Areas subject to multiple human interventions, such as grasslands, are particularly concerned. A Recurrent Neural Network multi-sensor regression approach (SenRVM), relying on the systematic acquisitions of Sentinel-1 SAR satellite, has been thereby proposed. It permits to retrieve vegetation indexes, derived from Sentinel- 2 optical imagery, despite significant cloud cover and with high sampling (6 days). The benefit of SenRVM for filling gaps in vegetation time-series describing agricultural practices is assessed. The proposed approach is compared with classical mono-sensor optical strategies. We adopt a synthetic dataset with large gaps. This realistically mimicks challenging conditions in grassland exploitation detection. Results obtained both for exploited and stable parcels satisfactorily demonstrate the relevance of our approach.