[process] MapSPAM Create Market Accessibility

This process is part of the MapSPAM series on spatial production. It is created as an interim process using the listed datasets below. This process involves setting a new variable derived from the grid-level estimates of rural population (GPW v4.0). The detailed procedure for measuring MapSPAM Access is presented in the listed Supplement document (Section S11).

"We create a measure of market accessibility (Accessi) from the grid-level estimates of rural population."
Yu, Qiangyi; You, Liangzhi; Wood-Sichra, Ulrike; Ru, Yating; Joglekar, Alison K. B.; Fritz, Steffen et al. (2020): A cultivated planet in 2010 – Part 2: The global gridded agricultural-production maps. In: Earth Syst. Sci. Data 12 (4), S. 3545–3572. DOI: 10.5194/essd-12-3545-2020.