3.2. Temporal relationships
Temporal variables like hours of sunlight, temperature and rain have significant influence on the crop growth. Therefore the trend of these variables needs to be analyzed. Via the Royal Netherlands Meteorological Institute information about these variables can be retrieved. A historical analysis of these variables can be made and compared to the current weather to gain insight in the extent and manner in which the current growth season deviates (weather wise) from previous years.
From satellite images the Normalized Difference Vegetation Index (NDVI) values can be deduced. These values serve as an indication of the amount of photosynthetically active vegetation on the parcel. Using historical analysis a crop and even variety specific NDVI curve has to be established which can be used to monitor the vegetation development characteristics using satellite imaging.
Also trend analysis must be performed on the NDVI data in combination with trend analysis on temporal variables. This analysis should focus on identifying relationships between the NDVI curves and temporal variables like sunlight, temperature and rain. Eventually these relationships are crucial in the formulation of data driven models used in the creation of “Task Map 2.0”.
Figure 3 shows some of the collected NDVI data. The shown curves are related to the growth of seed-potatoes on four different parcels. Between these parcels there are variations in location, soil composition, crop management and other biophysical properties. These variations contribute to the differences between the curves. But also some similarities between the curves can be seen, like the magnitude of the minimum and maximum values, the point in time at which the increase of the curves starts and the (location specific) point in time at which the decrease of the curves starts. This shows the viability of finding crop specific NDVI curves and identification of relationships between the NDVI data and temporal variables.