Ploughing Marker
Basic info
Among the key indicators of effective agricultural land management is the detection of ploughing activity. Here, the ploughing marker plays a critical role, whether confirming the field's maintenance or ensuring compliance with regulations amidst subsidies shifting towards more environmentally conscious practices. In the latter scenario, it's typically important to ascertain whether fields are ploughed during restricted periods when such activity is prohibited.
The ploughing marker serves the crucial purpose of pinpointing periods when a field has been ploughed, resulting in exposed bare soil. While ploughing activity may not be directly observable in satellite imagery like Sentinel or Planet Fusion data, its effects manifest over time and can be discerned through careful analysis of signal values.
Further info
Ploughing induces a rapid transition from vegetated to bare soil surfaces, a transformation that registers in the signal values as a notable increase in bare-soil probability. The higher this probability, the more confidently we can infer the presence of freshly ploughed soil. By observing a sharp and substantial rise in this probability, we can deduce when ploughing occurred. The start of the ploughing interval is marked by the onset of this increase, while its end is signified by a plateauing of the probability value.
It's worth noting the inverse relationship between bare-soil probability and NDVI (Normalized Difference Vegetation Index) values, which reflect vegetation vigor. When bare-soil probability is high, NDVI values tend to be low, indicating diminished vegetation cover.
The corn field shown below was vegetated until end of September and had exposed bare soil in beginning of October. In this same period we observe a distinct increase of the bare-soil probability and drop of NDVI value which indicates the field was ploughed.
Marker output
The output of the marker are ploughing events, defined by distinct dates in the period when the bare-soil probablity significantly increased, and corresponding bare-soil probabilities on these dates. User can control the number of false positive and false negative events by setting the marker parameters, such as the required magnitude of rise in the bare-soil probablity for an event to be valid.
For a detailed description of the ploughing marker output, check the Marker Service API documentation.
Links
Blog post about Bare-soil marker