Object-oriented change detection for the city of Harare,Zimbabwe

Object building and the extraction of homogeneous landscape units on which spatial statistics can be applied is useful in assessing land use and land cover change. Object-oriented processing techniques are becoming more popular compared to traditional pixel-based image analysis. A hierarchical image segmentation approach was adopted to extract the objects from multi-temporal Landsat images over Zimbabwe. The spatial arrangement of t₀ and t₁ objects was independent as the segmentation process was independently applied, although object change of t₁ was based on t₀ boundaries. We applied a Standardized, Object Oriented, Automatic Classification (SOOAC) method based on fuzzy logic. The error matrix for the TM image had an overall accuracy of 95.6% and a KIA value of 94.7%, the ETM showed slightly lower overall accuracy. Various LULC changes were identified over the 13 year period per object and also per class, mainly vegetation decrease. Object-oriented change information is necessary in decision support systems and uncertainty management strategies. This approach addresses some of the major issues in object-based GIS change analysis as it is based on stable object geometry.     

Survey of Fusarium moniliforme (F. verticillioides) and production of fumonisin B1 in cereal grains and oilseeds in Zimbabwe.

In a national survey carried out in 1995 and 1996, the distribution of Fusarium moniliforme (= F. verticillioides) and fumonisin B1 (FB1) levels in cereals and oilseeds from Zimbabwe were analyzed. The results of this study showed that the incidence of F. moniliforme and other Fusarium species and levels of FB1 generally decreased from regions with high rainfall and annual moderate temperatures to low rainfall regions. There was no Fusarium contamination and FB1 was not detected in sunflowers and soybeans. The incidence of F. moniliforme and its metabolite exhibited a substrate preference with high incidences of Fusarium species and high FB1 levels being recorded for maize followed by wheat, rapoko and sorghum.