GIS Models and Modeling Chapter 14

Introduction A model is a simplified representation of a phenomenon or system A model is a simplified representation of a phenomenon or system GIS modeling is as the use of GIS in the process of building models with spatial data. GIS modeling is as the use of GIS in the process of building models with spatial data. spatial data spatial data use of modeling use of modeling discipline specific discipline specific

GIS Modeling GIS assists modeling GIS assists modeling Integration of different sources then able to link and display together. Integration of different sources then able to link and display together. Vector or raster? Vector or raster? Raster: continuous, remotely sensed Raster: continuous, remotely sensed Vector: well defined locations and shapes or network. Vector: well defined locations and shapes or network. Can be integration of vector and raster. Can be integration of vector and raster. Just GIS or linked to other packages? Just GIS or linked to other packages?

Three Scenarios Loose coupling Loose coupling transfer of files to other programs transfer of files to other programs export export example statistical packages example statistical packages Tight coupling Tight coupling common user interface or menu selection to call common user interface or menu selection to call Embedded system Embedded system menus to call subsystems (ESRI products) menus to call subsystems (ESRI products)

Binary models A binary model uses logical expressions to select map features from a composite map or multiple grids. A binary model uses logical expressions to select map features from a composite map or multiple grids. Map overlay to prepare for vector query Map overlay to prepare for vector query Multiple grid process for raster Multiple grid process for raster Siting common application with multiple criteria (example Conservation Reserve Program) Siting common application with multiple criteria (example Conservation Reserve Program)Conservation Reserve ProgramConservation Reserve Program

Binary models Binary models can be used for change detection. Binary models can be used for change detection. Sometimes binary models are used at the beginning stage of modeling. Sometimes binary models are used at the beginning stage of modeling.

Index Models An index model used the index value calculated from a composite map or multiple grids to produced a ranked map. An index model used the index value calculated from a composite map or multiple grids to produced a ranked map. Selected variables are evaluated at two levels Selected variables are evaluated at two levels Relative importance, assigning a weight Relative importance, assigning a weight Observed values are evaluated and given scores. Observed values are evaluated and given scores. ArcView Model Builder ArcView Model Builder Suitability and vulnerability analysis Suitability and vulnerability analysis

Regression Models Regression model relates a dependent variable to a number of independent variables in an equation. Regression model relates a dependent variable to a number of independent variables in an equation. Linear regression is used when the dependent variables and independent variables are all numeric. Linear regression is used when the dependent variables and independent variables are all numeric. Logistic regression is used when the dependent variable is a binary phenomenon and the independent variables are categorical or numeric. Logistic regression is used when the dependent variable is a binary phenomenon and the independent variables are categorical or numeric.

Process Models A process model integrates existing knowledge about the environmental processes in the real world into a set of relationships and equations for quantifying the process. A process model integrates existing knowledge about the environmental processes in the real world into a set of relationships and equations for quantifying the process. Universal Soil Loss Equation (USLE) Universal Soil Loss Equation (USLE) Agricultural Nonpoint Source (AGNPS) Agricultural Nonpoint Source (AGNPS) Soil and Water Assessment Tool (SWAT) Soil and Water Assessment Tool (SWAT) Typically raster-based Typically raster-based Most commercial GIS do not offer. Most commercial GIS do not offer.