For the remaining twenty metres the deviation from the line does not exceed two centimetres. In field measurements, farmers have expressed great satisfaction with the performance. Fluctuations in path are no more than the fluctuations in the row crop and the system does indeed relieve the driver of a great deal of stress. Related vision projects Broccoli heads must be sorted at a rate of five heads per second, so that they can be packed for the appropriate markets. There is also a need to trim the stems to a variety of lengths according to the country of destination.
Classification is made according to size, shape, colour and length of stem.
For the choice markets, the top view of the head must be well rounded with no missing or deformed florets while the side-view must reveal a sufficient 'dome'. There must be no patches of yellowing representing over ripeness and the stem must be sufficiently long to allow trimming to the desired length. Rather than direct massive computing power at the task, we have succeeded in using substantially the same image analysis hardware that is used in the tractor guidance project. To gain speed, size is assessed by measuring the centre-line dimensions of the head, rather than by counting pixels over its area. If the head is badly deformed, this will of course give an erroneous measure.