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Distance Road network Transportation means
Primitive measures
Distance (time) from supply Simply potential model
Ai j S jdij
Supply-demand ratio within an area FCA with a radius/box FCA with a travel time range
a hybrid approach
a kernel density function a three-zone approach
Generalizing “distance decay”
Validation
Modeling actual supply-demand interactions
0 2.5 5
Miles 10
±
Legend
Accessibility Score
0.003876 - 0.004886 0.003218 - 0.003875 0.002464 - 0.003217 0.001727 - 0.002463 0.000986 - 0.001726 0.000000 - 0.000985 County Boundary
±
Spatial Accessibility by 2-step FCA Method
Legend
Accessibility Score
0.003876 - 0.004886 0.003218 - 0.003875 0.002464 - 0.003217 0.001727 - 0.002463 0.000986 - 0.001726 0.000000 - 0.000985 County Boundary
locations j within the travel time range from i
(catchment Zi). 2b. Sum up the supply to demand ratios at these supply
locations:
Ai Rj (S j / Pk )
jZi
Miles
0 12.5 25
50
75
Socio-cultural Barrier Scores (Factor 2)
±
Socio-cultural Barrier Scores (Factor 2)
Legend
FACTOR2
-1.597400 - -0.454300 -0.454299 - -0.014900 -0.014899 - 0.728000 0.728001 - 1.768700 1.768701 - 3.222300 3.222301 - 6.145200 County Boundary
0 2.5 5
Miles 10
±
Legend
FACTOR2
-1.597400 - -0.454300 -0.454299 - -0.014900 -0.014899 - 0.728000 0.728001 - 1.768700 1.768701 - 3.222300 3.222301 - 6.145200 County Boundary
Contents
The issue of access GIS-based accessibility measures Optimization towards equal access Application in healthcare access
PHSA designation and late-stage cancer
k within a travel time range from j (catchment Cj). 1b. Compute the supply to demand ratio within Cj:
Rj S j / Pk kC j
2a. For each demand location i, search all supply
Socio-cultural Barriers (Factor 2)
High Healthcare Needs
(Factor 3)
Female-headed households (%) Population in poverty (%) Nonwhite minorities (%) Households w/o vehicles (%) Home ownership (%) Households with linguistic isolation (%)
0 2.5 5
Miles 10
±
Legend
FACTOR3
-7.376800 - -1.760400 -1.760399 - -0.702300 -0.702299 - 0.023100 0.023101 - 0.715200 0.715201 - 1.697400 1.697401 - 5.786100 County Boundary
Concluding comments
Access Matters!
Convenience of access to activities
job, school, healthcare, park, public service, shopping …
Access defines “location” Spatial
AND secondary indicator (factor 3) 1 standard deviation above mean
S1 S2 ... Sn S
m
where Vj
Dk
d
kj
k 1
Value of optimization
Emphasizing the equality issue Identifying over- and under-capacity
of supply Guiding planning and public policy in
From S/D Ratio to FCA
Simply S/D Ratio FCA with a Radius
Improvements Within-unit variation Cross-border
Limitations Straight-line S-D beyond radius
Miles
0 12.5 25
50
75
High Health Care Need Scores (Factor 3)
±
High Health Care Need Scores (Factor 3)
Legend
FACTOR3
-7.376800 - -1.760400 -1.760399 - -0.702300 -0.702299 - 0.023100 0.023101 - 0.715200 0.715201 - 1.697400 1.697401 - 5.786100 County Boundary
Households with >1 person per room (%)
Population w/o high-school diploma (%) Median income ($)
High needs Population (%)
Spatial Accessibility by 2-step FCA Method
Medical Geography: Health Care Accessibility and Implications
Fahui Wang
Fred B. Kniffen Professor of Geography Louisiana State University
June 17, 2010 @ CNU
0 2.5 5
Miles 10
±
Legend
FACTOR1
-2.011300 - -0.462800 -0.462799 - 0.100000 0.100001 - 0.933300 0.933301 - 1.888600 1.888601 - 3.161700 3.161701 - 5.872100 County Boundary
Federal programs: MUP & HPSAs Calls for better measure of
accessibility
Consolidating nonspatial variables
Non-spatial
Socioeconomic Disadvantages
(Factor 1)
jZi
kC j
Generalizing “distance decay”
as a continuous function
a power or exponential function a Gaussian function
as a discrete variable
dichotomous as in 2SFCA multiple as in E2SFCA
2-step floating catchment area: 2SFCA
Scale availability at each supply location
Sum up accessible supplies around each demand location
2SFCA Recap
1a. For each supply location j, select all demand locations
Miles
0 12.5 25
50
75
Socioeconomic Disadvantage Scores (Factor 1)
±
Socioeconomic Disadvantage Scores (Factor 1)
Legend
FAC源自文库OR1
-2.011300 - -0.462800 -0.462799 - 0.100000 0.100001 - 0.933300 0.933301 - 1.888600 1.888601 - 3.161700 3.161701 - 5.872100 County Boundary
Miles
0 12.5 25
50
75
Integrating Spatial and Nonspatial Factors
Geographic Area
Primary Indicator (spatial accessibility score) < 1/3500 Primary Indicator (spatial accessibility score) < 1/3000
demand locations by adjusting the amounts of supplies at given supply locations.
A Quadratic Programming Approach
min
mn
(
S
j
d
ij
a)2
V i1 j1
j
Subject to
Where you are
Nonspatial
Who you are
Social justice and public policy
Measurement
How scarce are the services?
Supply vs. Demand (ratio)
How far are demands from supplies?
closing the gap
Application in Healthcare Access: HPSA designation
U.S. ranks behind in health performance
deep disparities in access to care and health outcomes
Individual travel behavior Aggregated travel pattern
Optimization
Towards equal accessibility Formulated as a planning problem minimizing accessibility gaps among
Primitive measures
Distance (time) from supply Simply potential model
Ai j S jdij
Supply-demand ratio within an area FCA with a radius/box FCA with a travel time range
a hybrid approach
a kernel density function a three-zone approach
Generalizing “distance decay”
Validation
Modeling actual supply-demand interactions
0 2.5 5
Miles 10
±
Legend
Accessibility Score
0.003876 - 0.004886 0.003218 - 0.003875 0.002464 - 0.003217 0.001727 - 0.002463 0.000986 - 0.001726 0.000000 - 0.000985 County Boundary
±
Spatial Accessibility by 2-step FCA Method
Legend
Accessibility Score
0.003876 - 0.004886 0.003218 - 0.003875 0.002464 - 0.003217 0.001727 - 0.002463 0.000986 - 0.001726 0.000000 - 0.000985 County Boundary
locations j within the travel time range from i
(catchment Zi). 2b. Sum up the supply to demand ratios at these supply
locations:
Ai Rj (S j / Pk )
jZi
Miles
0 12.5 25
50
75
Socio-cultural Barrier Scores (Factor 2)
±
Socio-cultural Barrier Scores (Factor 2)
Legend
FACTOR2
-1.597400 - -0.454300 -0.454299 - -0.014900 -0.014899 - 0.728000 0.728001 - 1.768700 1.768701 - 3.222300 3.222301 - 6.145200 County Boundary
0 2.5 5
Miles 10
±
Legend
FACTOR2
-1.597400 - -0.454300 -0.454299 - -0.014900 -0.014899 - 0.728000 0.728001 - 1.768700 1.768701 - 3.222300 3.222301 - 6.145200 County Boundary
Contents
The issue of access GIS-based accessibility measures Optimization towards equal access Application in healthcare access
PHSA designation and late-stage cancer
k within a travel time range from j (catchment Cj). 1b. Compute the supply to demand ratio within Cj:
Rj S j / Pk kC j
2a. For each demand location i, search all supply
Socio-cultural Barriers (Factor 2)
High Healthcare Needs
(Factor 3)
Female-headed households (%) Population in poverty (%) Nonwhite minorities (%) Households w/o vehicles (%) Home ownership (%) Households with linguistic isolation (%)
0 2.5 5
Miles 10
±
Legend
FACTOR3
-7.376800 - -1.760400 -1.760399 - -0.702300 -0.702299 - 0.023100 0.023101 - 0.715200 0.715201 - 1.697400 1.697401 - 5.786100 County Boundary
Concluding comments
Access Matters!
Convenience of access to activities
job, school, healthcare, park, public service, shopping …
Access defines “location” Spatial
AND secondary indicator (factor 3) 1 standard deviation above mean
S1 S2 ... Sn S
m
where Vj
Dk
d
kj
k 1
Value of optimization
Emphasizing the equality issue Identifying over- and under-capacity
of supply Guiding planning and public policy in
From S/D Ratio to FCA
Simply S/D Ratio FCA with a Radius
Improvements Within-unit variation Cross-border
Limitations Straight-line S-D beyond radius
Miles
0 12.5 25
50
75
High Health Care Need Scores (Factor 3)
±
High Health Care Need Scores (Factor 3)
Legend
FACTOR3
-7.376800 - -1.760400 -1.760399 - -0.702300 -0.702299 - 0.023100 0.023101 - 0.715200 0.715201 - 1.697400 1.697401 - 5.786100 County Boundary
Households with >1 person per room (%)
Population w/o high-school diploma (%) Median income ($)
High needs Population (%)
Spatial Accessibility by 2-step FCA Method
Medical Geography: Health Care Accessibility and Implications
Fahui Wang
Fred B. Kniffen Professor of Geography Louisiana State University
June 17, 2010 @ CNU
0 2.5 5
Miles 10
±
Legend
FACTOR1
-2.011300 - -0.462800 -0.462799 - 0.100000 0.100001 - 0.933300 0.933301 - 1.888600 1.888601 - 3.161700 3.161701 - 5.872100 County Boundary
Federal programs: MUP & HPSAs Calls for better measure of
accessibility
Consolidating nonspatial variables
Non-spatial
Socioeconomic Disadvantages
(Factor 1)
jZi
kC j
Generalizing “distance decay”
as a continuous function
a power or exponential function a Gaussian function
as a discrete variable
dichotomous as in 2SFCA multiple as in E2SFCA
2-step floating catchment area: 2SFCA
Scale availability at each supply location
Sum up accessible supplies around each demand location
2SFCA Recap
1a. For each supply location j, select all demand locations
Miles
0 12.5 25
50
75
Socioeconomic Disadvantage Scores (Factor 1)
±
Socioeconomic Disadvantage Scores (Factor 1)
Legend
FAC源自文库OR1
-2.011300 - -0.462800 -0.462799 - 0.100000 0.100001 - 0.933300 0.933301 - 1.888600 1.888601 - 3.161700 3.161701 - 5.872100 County Boundary
Miles
0 12.5 25
50
75
Integrating Spatial and Nonspatial Factors
Geographic Area
Primary Indicator (spatial accessibility score) < 1/3500 Primary Indicator (spatial accessibility score) < 1/3000
demand locations by adjusting the amounts of supplies at given supply locations.
A Quadratic Programming Approach
min
mn
(
S
j
d
ij
a)2
V i1 j1
j
Subject to
Where you are
Nonspatial
Who you are
Social justice and public policy
Measurement
How scarce are the services?
Supply vs. Demand (ratio)
How far are demands from supplies?
closing the gap
Application in Healthcare Access: HPSA designation
U.S. ranks behind in health performance
deep disparities in access to care and health outcomes
Individual travel behavior Aggregated travel pattern
Optimization
Towards equal accessibility Formulated as a planning problem minimizing accessibility gaps among