raster_runif: a raster with random values between 0 and 1 for every cell of the datasource GRTSmaster_habitats

The raster_runif data source covers the Flanders and Brussels region and has a resolution of 32 meters. The raster cells with non-missing values match the value-cells of the GRTSmaster_habitats data source  with a small buffer added. Every raster cell has a random value between 0 and 1 according to the uniform distribution. 

An example usage of this raster is its combination with the GRTSmaster_habitats and habitatmap_stdized data sources in order to draw an equal probability sample of habitat types in Flanders. Habitatmap_stdized contains polygons that are partially or fully covered by habitat types. The proportion of a certain type within a polygon is provided by the phab value. We can draw an equal probability sample size n for a certain habitat type as follows:

• select all raster cells of GRTSmaster_habitats that overlap with the sampling frame of the target habitat type
• keep the raster cells for which the raster_runif value is lower than the phab value of the habitat type within the polygon
• finally select the n raster cells with the lowest GRTS ranking number.

The R-code for creating the raster_runif data source can be found in the GitHub repository 'n2khab-preprocessing' at commit ede43a4.

A reading function to return the data source in a standardized way into the R environment is provided by the R-package n2khab.