This section presents three examples of typical processing chains and graphical outputs generated by the SPIRITS software. They provide information that is commonly presented when monitoring crops or drought over large areas. Currently, these SPIRITS outputs are directly used in the agro-meteorological and early warning bulletins produced on a regular basis by a wide range of agencies.
The first example concerns the production of a time series of NDVI anomaly maps (absolute deviation from the long term average, in this case calculated for 1999–2010) derived from ten-daily images of SPOT-VGT over the Horn of Africa in 2011. Fig. 2 outlines the steps involved in the workflow, while map outputs are shown in Fig. 3. Note that anomalies are reported here on a qualitative scale based on user-defined thresholds. The absolute anomaly values could also be plotted, and map classes and colours could be changed depending on user preferences.