Africover interpretation chain

The development of the Africover land cover map is based on the multi-phase image interpretation approach, which was successfully used by FAO in a number of projects.

The real interpretation chain is preceded by a series of preparatory activities:

• Selection, geocoding and enhancement of satellite data set
• Selection, ordering of country ancillary data
• Selection of local photo-interpreters
• Training on the Africover methodology and tools

The interpretation chain main phase

• Creation of a “virtual” preliminary legend: After a consultation of national ancillary data, local knowledge of the area or rapid field survey in selected zones, inventory of the "possible" landcover classes of the area is done using LCCS. This is just a starting list of possible landcover classes.
  
• Preliminary interpretation: A delineation of land cover polygons as they can be seen from the satellite data will be done. During this phase the “virtual” legend will be continuously updated/modified to adhere to reality as seen from remote sensing data
  
• Fieldwork preparation: On the bases of the interpretative uncertainty highlighted during the preliminary interpretation, a portion of map units will be selected for field checking. This first set of points will be integrated, if necessary, by an extra set of checks to assure a good statistical representation of each main landcover classes.
  
• Fieldwork execution
  
• Field data elaboration: An “intermediate” interpretation accuracy will be done using field data. This information will allow the photo-interpreters to evaluate in a rather objective way the work done in the preliminary phase of interpretation. At this stage all the necessary information exist to re-update the preliminary legend. Classes without full accuracy can be generalized. Other classes with a clean pattern on the images validated by the field observation will be added. This work leads to the creation of a "final legend".
  
• Final interpretation: Using a base as the "final legend", a recheck of the interpretation is done.
  
• Digital database set up