Choose the annual croplands category if the fields looks like they contain crops that are planted and harvested during a single year (or occasionally after a few seasons).
This is the primary class of agriculture we will see in our labelling efforts, and the one we spend most of our time labelling. It is also one of the most variable classes of agriculture. Here we provide a look at some of that variability, providing two important guidelines to help avoid confusion with other classes such as tree crops and fallow.
Guideline 1: Annual cropland can look either bare or planted in the imagery
The fields that we classify as annual cropland can look like they are either bare soil or growing a crop, even during the growing season. Here’s an extremely complicated site in Ghana. The blue arrows show sites where the field appear both bare and to be growing a crop. Both should be labelled as annual cropland.
Guideline 2: Annual cropland often has trees growing in it
All the fields that should be labelled (blue arrows) in the Planet growing image below have trees growing in them. Looking at the basemap imagery (right panel) really helps to see these trees.
Sometimes the trees in the field look as if they could either be tree crops, or could be a mix of tree crops and annual crops (i.e. agroforestry), as in the image below (see blue arrows, and polygons in lower right). These fields could technically be classified as croplands also, because the trees look they are deliberately interspersed with annual cropland, and the trees are planted at perhaps lower density than you would expect to see in an orchard or tree plantation. However, in this project we do not label them, per rule 6) because they have a strong predominance of tree crops, and this might also confuse the mapping algorithm.
In addition to these two agroforestry fields, there are other ones nearby that are more clearly puretree crops, indicated by the white arrows. As these are tree crops–we also do not label them (see rule 6). Factors helping to distinguish tree crops are:
Their high density (distinguishing them from annual cropland), and;
Regular size and spacing (distinguishing them from unmanaged woodland, which is non-agricultural land).
Note that we determined these locations to be tree crops by looking at the basemap imagery to see these two details, which are not really visible in the Planet imagery.
We cover tree crop classification in more detail in the next rule (Rule 6).