Introduction to Spatial Information in Modeling Concepts and the GIS Weasel

Obviously, real land features do enter a model Instead, a model uses a description of land feature attributes Representation

Obviously, real land features do enter a model Instead, a model uses a description of land feature attributes All attributes of land feature cannot be described to model model developer must choose most important attributes Representation

Obviously, real land features do enter a model Instead, a model uses a description of land feature attributes All attributes of land feature cannot be described to model model developer must choose most important attributes  Models use concepts to represent land features Representation

-for example, “hillslope”: area that begins along a stream channel and extends to the elevation ridge above that stream. Representation

-for example, “hillslope”: area that begins along a stream channel and extends to the elevation ridge above that stream.  attributes: elevation, slope, aspect Representation

- for example, “hillslope”: area that begins along a stream channel and extends to the elevation ridge above that stream.  attributes: elevation, slope, aspect - Concept of “hillslope” is not entered into the model - Attributes of “hillslope” are put into the model Representation

- attributes that are put into the model are called “parameters” -For example, slope, aspect, elevation are parameters of the hillslope - although other attributes exist, model may not use this information Parameters

- Again, a c oncept has attributes - An example of the concept is described by parameter values Instance

- Again, a c oncept has attributes - An example of the concept is described by parameter values -For example, a real hillslope may have Slope = 15% Aspect = East Elevation = 3000 meters - called an “instance” of the concept Instance

- Distributed models allow more than one instance of a concept -For example, 10 hillslopes may exist in a watershed -Model needs to organize instances - uses ARRAYS -Standard to programming and mathematics Arrays

- arrays contain a number of instances -Depends on how many examples of the concept you wish to describe Dimension

- arrays contain a number of instances -Depends on how many examples of the concept you wish to describe - the number of instances is called the “dimension” of the array -Can also be thought of as the “size” of the array Dimension

- arrays contain a number of instances -Depends on how many examples of the concept you wish to describe - the number of instances is called the “dimension” of the array -Can also be thought of as the “size” of the array -For example, if you have 10 instances of hillslopes in your watershed:  There are 10 values of slope  There are 10 values of aspect  There are 10 values of elevation Dimension

- The arrays might appear as: -Slope[10] -Aspect[10] -Elevation[10] - The dimension of each of the parameter arrays is ’10’ Dimension

1. real land features not put into model 2. model uses concepts to represent data 3. model does not take concepts as input 4. model does not (usually) take GIS data as input 5. model does take parameters as input -parameters describe instance of concept 6. more than one instance may exist - parameters organized into arrays -Size of arrays called dimension Review

- model may use more than one spatial feature concept - for example, a model may use “hillslope” and “channel” Multiple Dimensions

- model may use more than one spatial feature concept - for example, a model may use “hillslope” and “channel” - model must understand the difference between the concepts and the parameter arrays which describe them Multiple Dimensions

- model may use more than one spatial feature concept - for example, a model may use “hillslope” and “channel” - model must understand the difference between the concepts and the parameter arrays which describe them - dimensions are therefore given names - for example, The dimension of the hillslope concept could be called “nhillslope” The dimension of the channel concept could be called “nchannel” Multiple Dimensions

- dimension names can refer to types of spatial concepts - for example, “nhillslope” and “nchannel” - dimensions names can also refer to types of non-spatial concepts - for example, “nmonths” and “ncurve” Dimension Names

- GIS can help with spatial dimensions - for example, it can be used to make a map of “nhillslope” - for example, it can be used to make a map of “nchannel” - GIS can not (usually) help with non-spatial dimensions - for example, can not make a map of “nmonths” - for example, can not make a map of “ncurves” Role of GIS

- the user must know the model concepts being described with dimensions of parameters !! - the user must use GIS correctly!! - can make a map of sub-watersheds and derive parameters - model uses this information to represent “hillslopes” - poor model results Using GIS

- the GIS Weasel is very easy to make maps with - the GIS Weasel does not have model-specific knowledge - for example, it does not know the difference between “nhillslope” and “nchannel” - again, the user must know the model concepts that are described with parameters !! - the user must use the GIS Weasel tools correctly!! GIS Weasel

General procedure: 1. use the GIS Weasel to make a map of each type of spatial feature 2. tell the GIS Weasel which map represents which dimension 3. derive the parameters of each dimension GIS Weasel & Modeling

For example, 1. make maps -make a map of hillslopes called “my_hillslopes” -make a map of stream channels called “my_channels” GIS Weasel & Modeling

For example, 1. make maps -make a map of hillslopes called “my_hillslopes” -make a map of stream channels called “my_channels” 2.associate maps with dimension -“my_hillslopes” represents the dimension “nhillslope” -“my_channels” represents the dimension “nchannel” GIS Weasel & Modeling

For example, 1. make maps -make a map of hillslopes called “my_hillslopes” -make a map of stream channels called “my_channels” 2.associate maps with dimension -“my_hillslopes” represents the dimension “nhillslope” -“my_channels” represents the dimension “nchannel” 3.derive the parameters of each dimension -apply GIS Weasel routines to create parameter output that is organized by dimension names GIS Weasel & Modeling