This chapter presents a co-produced research that took place since 2009 between interdisciplinary scientists and herders from a Sami reindeer community in northern Sweden. This research was conceived in response to a participatory mapping program, the Reindeer Husbandry Plan (RHP), led by the Swedish Forest Agency. The RHP is based on a digital tool compiling and mapping habitat use by reindeer herding communities. Mapping land use, even with participatory methods, is a powerful tool which could lead to the best or the worst, despite initial good intentions. Knowing how zoning and mapping the best available pastures was a complex issue in a changing subarctic environment, we wondered how the RHP would succeed in such a difficult enterprise. How could Sami herders map 'good pastures' which can suddenly become bad, while less good pastures, can, according to circumstances, become the best choice? The purpose of the co-produced project was to include the complexity of Sami herders’ knowledge and worldviews, their land management and their science of the snow, into the RHP, while developing an original methodology to map the use of winter grazing lands by Sami reindeer herders in northern Sweden.