- Slides: 19
Spatial Interaction & Spatial Behavior
spatial interaction: the movements of peoples, ideas, & interaction commodities within & between places Determinants of interaction between two places: communication flows, travel patterns, & migration flows -- Why do goods/people move from place to place? -- Personal examples of your “spatial interaction”?
Models of Spatial Interaction How do we create models to describe the pattern of flows between different places? Through either micro or macro theories Ullman’s flow determining model: I. Complementarity II. Transferability III. Intervening Opportunity
Complementarity: supply of something in one place & demand for it in another
Transferability: exchange of product occurs between both sides and depends on… 1. The characteristics/value of a product 2. The distance (in time and money penalties) over which it needs to be 3. moved. The ability of the commodity to bear the costs of movement. • transferability decreases with distance
Intervening Opportunity: a closer option will change interaction intervening opportunity increases with distance
You have a product in California that you need but the cost of transportation is too much. This is an example of A. complementarity and transferability B. complementarity but no transferability C. an intervening opportunity D. transferability but no complementarity E. A, B, C, & D
Measuring Spatial Interaction i. Distance Decay (the friction of distance) ii. The Gravity Model (size & distance affect interaction) iii. The Potential Model iv. Movement Biases (distance, direction, & network bias)
“Distance decay”: the decline of activity with increasing distance from the point of origin inverse-square relationship (j-curve)
Density of BMIhealthy food outlets in New York City… Closer to a BMI health food store, what happens to obesity levels?
What variations in distance decay curves might you expect if you were to plot shipments of the following: 1. concrete 2. potato chips 3. Nike shoes What do these respective curves tell us about transferability?
ii. The Gravity Model 1. A model that expresses interaction between two places as a function of: -the size of the two places (population) size -the distance between them distance 2. The physics of size versus distance * Sir Isaac Newton said: “Any two objects attract each other with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between them” * Big things attract more than smaller things, and things closer to each other have a stronger mutual
The Gravity Model “In Action” • Larger shopping centers attract more than smaller ones. • Larger cities = better lives/fortune/culture • Other important factors • Size • Social status • Diversity of commodities offered • Travel time • Cost
Predicting Travel Routes
Predicting Computer Purchases
• Law of retail gravitation: a predictive model to select Law of retail gravitation the most profitable business locations Breaking point location: beyond it, another town dominates that market area. How does this affect, say Sawgrass Mills? Or nightlife on South Beach?
iii. The Potential Model Measures interactions between one location & every other location Measures the potential amount/weight of interactions (good for studying retail behavior, marketing, broadcasting) E. g. You have more than two stores to choose from.
Predict Interactions between sites A-D with 1 -9…
iv. Movement Bias 1. What creates the movement bias problem? 1. Natural and cultural barriers preventing ideal gravity/flow model 2. Why are we “forced” into certain kinds of spatial behaviors? - DISTANCE BIAS: Often prioritizes short movements vs. long - DIRECTIONAL BIAS: From a given origin, flows are not random. (North/South or East/West) - NETWORK BIAS: When nodes are connected via links, those links are more likely to be used.