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Visualization of Geospatial Data by Component Planes and U-matrix Marcos Aurélio Santos da Silva Antônio Miguel Vieira Monteiro José Simeão de Medeiros
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Problem: Mapping urban social exclusion/inclusion in São José dos Campos, SP. Data – 8 socioeconomic indexes computed from raw IBGE dataset; Questions – How the dataset is distributed? – How each variable correlates with each other? – Is there some spatial correlation between the feature and physical spaces.
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342 urban census regions of São José dos Campos, São Paulo.
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Socioeconomic data [-1,+1] 1. Familiar Income (IFH); 2. Educational Development (ED); 3. Educational Stimulus (ES); 4. Longevity (LONG); 5. Environmental Quality (EQ); 6. Home Quality (PQ); 7. Concentration of Family Headed by Women (CWFH); 8. Concentration of Family Headed by Illiterate Women (CIWFH); -1: Means high exclusion level;+1: Means high inclusion level
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Neurocomputing
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Self-Organizing Maps (SOM)
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Unsupervised; Iterative; Batch (codevectors are updated after each iteraction) Gaussian neighborhood kernel function; SOM Learning process
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Self-Organizing Maps (SOM) SOM Properties Raw dataset (each rectangle represents a feature vector (v i ) Learning {v 1, v 2... }
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Relation between SOM and Spatial Map Neighborhood in the feature space Neighborhood in the physical space
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Visualization Algorithms Unified Matrix Distance (U-matrix) U-matrix map the codevectors values into a 2D display.
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Visualization Algorithms Component Planes (CP) For each variable
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Results
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Group2 20x15 Group1
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Group 2 Detected Outliers
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IFHED ESLONGEQ PQCIWFHCWFH High degree of similarity High degree of homogeinity
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Vertical Horizontal Diagonal \ Diagonal / Social Exclusion Direction on SOM Map
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Mapping SOM distribution into the Census Map
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Comparing with previous statistical results Statistical clustering (IEX) Neuro-clustering (SOM) Center-to-peripherical direction of urban social exclusion
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Tools CASAA (processing); SOM Toolbox Matlab (SOM’s visualization) TerraView (census map visualization) TerraLib (spatial data access library)
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TerraView CASAA
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Conclusions SOM worked well in the task of exploratory analysis of multivariated geospatial data; Component Planes can help us to discover spatial distribution of the phenomena; The size of SOM Map influences the final result learning process;
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Marcos Aurélio Santos da Silva e-mail: aurelio@embrapa.br Thanks !!
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