In Atfarm we allow to upload fields that are minimum 100m² in size (0.01 ha). We cannot handle smaller fields due to the satellite data provider. Fields that meet this requirement, we allow biomass monitoring.
To do variable rate application maps, the fields need to be larger. As the pixels at the boundaries of the fields may contain mixed information (e.g. half a pixel is crop and the other a road or a river), we need to exclude them from the calculations. This is the case for every pixel that is not 100% in the field (we call them boundary pixels). Technical minimum for the boundary handling algorithm is minimum one pixel with an 8 neighborhood of pixels (which is a pixel that is not in contact with the boundary) – therefore the minimum size is 3 by 3 pixels = 60*60 = 3600m²
Image 1: Example of a field with one single pixel with an 8 neighborhood – in this case, the 50 N of the center pixel is used also for the surrounding pixels
The minimum field size to get a variable rate application map with the boundary handling in the N-Sensor Algorithm is 4 by 3 pixels – that is the requirement to have more than one valid pixel to calculate a variable rate map, therefore, the minimum size is 80*60 = 4800m²
Image 2: Example of a field with two pixels with an 8 neighborhood – in this case, the 50 N and the 100N of the center pixels is used to calculate the values of the surrounding pixels