Modeling Spatial Problems

1
Modeling Spatial Problems

• Description of models.
• Models of surfaces.
• Cell-based calculations to fill the raster.
• Interpolating to fill the raster.

2
Description of Models

• A model is a representation of reality.
• Models are created as a simplified, manageable
  view of reality.
• Models help you understand, describe, or predict
  how things work.

3
Types of Models

• Representation models.
• Represent the objects in the landscape.
• Process models.
• Simulate processes in the landscape.
• Data Models.
• Vector
• Raster
• TIN

4
Representation Models

• Describe the objects in a landscape through a set
  of data layers.

5
Representation Models

• Common data models/descriptive models.
• Spatial relationships within an object (the shape
  of a building).
• Between the other objects in the landscape (the
  distribution of buildings).
• Model the attributes of the objects (who owns
  each building).

6
Process Models

• Describe the interaction of the objects that are
  modeled in the representation model using map
  calculation.

7
Process Models

• Complexity can be added through logic.
• Map query by Boolean and logical operators.

8
Time Out for Definitions

• Boolean operators
• And, Or, XOr, Not
• Relational operators
• , gt, lt, ltgt, gt, lt
• Arithmetic operators
• , /, -, , Log, Exp, Sin, Cos, Sqrt

9
Process Models

• Suitability modeling where should I put it?
• Distance modeling how far is it?
• Hydrologic modeling where will the water flow
  to?
• Surface modeling what is the pollution level?

10
Process Models

• Additional complexity is added through
  specialized functions.
• Given particle size of eroded sediment and stream
  flow rate, how far will pollution go?

11
Process Models

• Sometimes hundreds of operations and functions
  may be necessary.

12
Process Model Implementation
13
Process Model Implementation

• Command line sequences from ArcInfo.
• Forest cover determination.
• If (sawlakesgr 0) sawcover 2, 2 water.
• Else if (sawlakesgr 1 sawctrec 3)
  sawcover 3, 3 forested.
• Else if (sawlakesgr 1 sawctrec 4)
  sawcover 4, 4 meadow-shrub.

14
Solving Spatial Problems

• State the problem.
• What is the goal?
• Break the problem down.
• Objectives.
• Identify the elements and their interactions.
• Create the necessary input datasets.

15
Types of Input Data

• Three representations of the world (data models).
• Collection of discrete features in vector format.
• Grid of cells with spectral or attribute data.
• Set of triangulated points modeling a surface.

16
Choosing Input Datasets
17
Choosing Input Datasets

• Understand the spatial and attribute
  relationships of the individual objects in the
  landscape.
• Which attributes within and between datasets are
  important for solving the problem.

18
Is the Focus on Features or Location?

• Modeling distinct objects with attributes and
  behavior vector.
• Locate features with significant precision
  vector.
• Modeling continuous objects with an attribute at
  a location raster or TIN.

19
What Types of Features Are Required?

• Modeling large features with values that vary,
  change with time, or have indistinct boundaries
  raster.
• Modeling features that characterize the shape of
  the earths surface TIN.
• River systems vector.
• Man-made features vector.

20
What Type of Analysis Is Required?

• Analyzing a surface TINs have broadest array of
  analytic functions. Rasters also work for some
  purposes.
• Analyzing a volume TIN.
• Dispersion of a plume raster.
• Proximity to features raster.
• Suitability analysis raster.

21
What Type of Analysis Is Required?

• Optimal location studies vector.
• Network analysis vector.
• Managing land records vector.
• Referencing postal location to map vector.
• Topological relationships vector.

22
What Types of Maps Are to Be Produced?

• Maps of areas with changing attribute values
  raster or TIN.
• Maps with fine detail of features vector.

23
Perform the Model Analysis

• Identify the tools to use to build the overall
  model.
• Basemap?
• Hydrologic analysis?
• Environmental analysis?
• Terrain analysis?

24
Verify the Model's Result

• Check the result from the model in the field.
• Compare several models.
• Reclassification.
• Normalization.

25
Implement the Result

• Field check other sites prior to printing final
  maps.