Trend-surface analysis revisted--a case history
Computers & Geosciences
Using the R statistical data analysis language on GRASS 5.0 GIS database files
Computers & Geosciences
Statistics and Data Analysis in Geology
Statistics and Data Analysis in Geology
Open Source GIS: A Grass GIS Approach
Open Source GIS: A Grass GIS Approach
R: a data analysis and statistical programming environment-an emerging tool for the geosciences
Computers & Geosciences
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Trend-surface analysis was carried out on data from morphometric parameters isobase and hydraulic gradient. The study area, located in the eastern border of Quadrilatero Ferrifero, southeastern Brazil, presents four main geomorphological units, one characterized by fluvial dissection, two of mountainous relief, with a scarp of hundreds of meters of fall between them, and a flat plateau in the central portion of the fluvially dissected terrains. Morphometric maps were evaluated in GRASS-GIS and statistics were made on R statistical language, using the spatial package. Analysis of variance (ANOVA) was made to test the significance of each surface and the significance of increasing polynomial degree. The best results were achieved with sixth-order surface for isobase and second-order surface for hydraulic gradient. Shape and orientation of residual maps contours for selected trends were compared with structures inferred from several morphometric maps, and a good correlation is present.