The ActivityField can be identical to a Field or is part of a Field. In many cases it will correspond with a CropField, but this is not always the case; 1) Activities can be performed on a Field as a whole, when there are no crops grown, 2) Activities can be performed on more CropFields bordering each other, when there is a reason to distinguish them as CropFields, but operations can be executed as one activity and 3) Activities are performed on only a part of the CropField, like for example when a contractor is asked to harvest the headlands and fieldborders at a certain date and leave the field remnant for a later stage. To be discussed: Can an Activity Field exist over more growing seasons? What should be the starting and ending date?