Spatial InteractionSpatial Interaction&&

Spatial BehaviorSpatial Behavior

-- Why do goods/people move from place to place?

-- Personal examples of your “spatial interaction”?

spatial interactionspatial interaction: the movements of peoples, ideas, & commodities within & between places

Determinants of interaction between two places:  communication flows, travel patterns, & migration flows

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:Ullman’s flow determining model:I. ComplementarityII. TransferabilityIII. Intervening Opportunity

Models of Spatial InteractionModels of Spatial Interaction

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 product2. The distance (in time and money penalties) over which it needs

to be moved.3. 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 transferabilityB. complementarity but no transferabilityC. an intervening opportunityD. transferability but no complementarityE. A, B, C, & D

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)

Measuring Spatial InteractionMeasuring Spatial Interaction

“Distance decay”: the decline of activity with increasing distance from the point of origin

inverse-square relationship (j-curve)

Density of BMI-Density of BMI-healthy food healthy food outlets in New outlets in New York City…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. concrete2. potato chips3. Nike shoes

What do these respective curves tell us about transferability?

1.A model that expresses interaction between two places as a function of:

-the sizesize of the two places (population)-the distancedistance between them

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 attraction.

ii. The Gravity Modelii. The Gravity Model

The Gravity Model “In The Gravity Model “In Action”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• Effort

Predicting Travel RoutesPredicting Travel Routes

Predicting Computer Predicting Computer PurchasesPurchases

•Law of retail gravitationLaw of retail gravitation: a predictive model to select 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?

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.

iii.iii. The Potential ModelThe Potential Model

Predict Interactions between sites Predict Interactions between sites A-D with 1-9…A-D with 1-9…

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.

iv. Movement Biasiv. Movement Bias