Deliverable 2.3 presents design-based, model-assisted estimators for forest and environmental monitoring, focusing on totals, ratios (e.g., biomass per hectare), and changes between periods. It shows how to use auxiliary information from remote sensing and large plot datasets to improve precision while keeping estimates (approximately) unbiased, including methods that preserve geographic additivity and handle cases where different samples are used over time. It also summarizes how selected estimators are implemented in the nFIESTA component of the PathFinder platform, with addenda on combining panels and using map-based auxiliaries safely.