Fig. 1
From: Take five: about the beat and the bar of annual and 5-year periodic national forest inventories
Spatial grid design of the French annual forest inventory survey as adopted since 2005. The design is based on the interpenetrating panel approach. Each number corresponds to one panel/year one grid cell is assigned to, for a final periodicity of 5 years. The cells themselves define a square sub-grid, ensuring a yearly systematic spatial cover of the forest population (illustrated for years 1 and 4 in a, and 1 and 5 in b). For panel 1, the dots illustrate the within-cell random sampling of unit locations. a: Grid scheme for a base sampling grid. b: Alleviation of the sampling effort by a factor of 2 maintaining spatial systematicity (notion of level), used for the sampling of different vegetation categories (redrawn and adapted from Bouriaud et al. 2023)