The crop models in MCYFS where originally developed to simulate crop yield for a single location (or region) where weather, soil and crop characteristics are assumed homogeneous. To apply the crop models on a large scale the models have to be run for every location with a unique set of weather, soil and crop characteristics.
The weather and spatial and temporal crop characteristics are assumed to be homogeneous per grid cell of the 25x25km climate grid. The soil characteristics are assumed to be homogeneous per Template:Tablelink. The smallest cartographic unit of the soil map is called a which consists of variuos STU's. Only the relative amount of a STU within a SMU is know. All unique SMU's are stored in table Template:Tablelink, the relation between STU's and SMU's is stored in table Template:Tablelink.. The STU data are stored in table
When combining the weather, crop and soil datalayers we have to instersect the 25x25km climate grid with a map of the SMU's. This results in so-called Template:Tablelink.’s stored in table
Still the crop models have to be run for every unique combination of grid cell and STU (for every simulation unit) and the result need to be aggregated to a values per SMU by a weighted average of the simulation units it contains. The aggregated simulation results per EMU are stored in the table Template:Tablelink. With the existing relation between EMU's and grid cells the results can be aggregated to grid cells (stored in table Template:Tablelink).
In the Yield Forecasting module the simulated results are compared on a regional scale. The regional yield statistics are normally available at national (level 0) or at provincial level (level 1 or 2). To be able to aggregate model output to administrative regions it is necessary to know the relation between EMU's and administrative regions. Therefore the EMU's are intersected with a map of the administrative regions ( level 3). In this way results can be aggregated to any administrative level. The aggregated simulation results per administrative region are stored in the table Template:Tablelink.