XccessPoint Proposal

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Project Description

“This is what inequality looks like.” You Yenn Teo’s recent best seller book uncovers the heightened tension on social inequalities in Singapore. It has motivated to use to delve deeper into the current situations of inequality in Singapore. One way to understand the inequality is to examine the accessibility to many key essential facilities for an ordinary Singaporean living in Housing Development Board units. The aspect of accessibility to look into includes the distance to healthcare facilities (General Practitioner Clinics, Polyclinics and Hospitals), transportation infrastructure (MRT and Bus Stops) , schools, pre-school, police stations, and hawker centres for all HDBs in different planning subzones. We hope to develop an accessibility study tool for urban planners to better strategize the development of new facilities for achieving greater equality for an ordinary Singaporean. For instance, how would Land Transport Master Plan 2040 effectively improve the existing accessibilities to transport facilities.

Our team's objective is to analyse and determine how these facilities such as transportation, school and healthcare services would impact the accessibility level around HDB.

Motivation

The government has been finding sustainable ways to tackle the increasing inequality and stratification in Singapore.With constant development and improvement of infrastructure around Singapore, the impact on accessibility has not really been research upon.

Data Sources

Dataset	Description	Data Type	Source(s)
Singapore Regions	To facilitate urban planning, the Urban Redevelopment Authority (URA) divides Singapore into 5 regions, namely Central, West, North, North-East and East Regions.	SHP	Data Source
Singapore Planning Area	Indicative polygon of planning area boundary. To facilitate urban planning, the Urban Redevelopment Authority (URA) divides Singapore into 55 planning areas	SHP	Data Source
Singapore Planning Subzone	Indicative polygon of subzone boundary. The Planning Regions are divided into smaller Planning Areas. Each Planning Area is further divided into smaller subzones which are usually centred around a focal point such as neighbourhood centre or activity node.	SHP	Data Source
HDB	List of HDB location via postal code	CSV	Data Source
School facilities	List of education facilities in Singapore	CSV,KML	Data Source Data Source
Government Markets Hawker Centres	Contains Address of Hawker Centres in Singapore	KML	Data Source
Heathcare Facilities	Contains Address to Healthcare Facilities in Singapore	Website Information	Data Source Data Source
LTA Mrt station	The layer contains the locations of MRT station exits.	KML	Data Source
Bus Stops	All bus stops, bus interchanges, bus terminals in Singapore.	CSV	Data Source

Literature Review

Literature review of relevant research paper on spatial analysis of accessibilities are conducted to enhance our project methodology.

1.Site Suitability Evaluation for Ecotourism Using GIS & AHP: A Case Study of Surat Thani Province, Thailand

Study Objective:

This paper aims to identify and prioritize the potential ecotourism sites using Geographic Information System (GIS) and Analytical Hierarchy Process( AHP) in Surat Thani Province. The factors in consideration for suitability for the land ecosystems include landscape/naturalness, wildlife, topography, accessibility and community characteristics.

Visualization:

Suitability Map for Ecotourism in Surat Thani Province in Thailand

Schematic Representation of the Methodology

AHP Matrix for Pairwise Comparisons and the Consistency Ratio Estimation

Methodology

1.Determination of Weights using AHP

AHP is one extensively used Multi-Criteria Decision Making technique (developed by Saaty in 1980) used in structural decision making process for complex problems that involves multiple criteria across different hierarchical levels. Pairwise comparisons method is used to compare the criteria and allow for evaluation of relative significance of all parameters. Expert opinions were taken into consideration for the comparisons. Pairwise comparison uses a scale of 1 to 9 which 1 means having equal importance while 0 means having extreme importance. Reciprocal pairwise comparisons is used for opposite comparison of facilities.

2.Factoring in Decision Making Inconsistency

To ensure consistent judgement of decision makers, AHP efficiency criteria are measured by Consistency Relationship (CR = Consistency Index/Random Index). If CR is smaller than 0.10, degree of consistency will be fairly acceptable. Otherwise if it exceeds 0.10, inconsistencies exist in the evaluation process and we need to reject the pairwise comparisons and reiterate the process.

3.Land Suitability Assessment

The total suitability score “Si” for each land unit (i.e. each raster cell in the map) was calculated from the linear combination of suitability score obtained for each factor and criteria involved.

where “n” is the number of factors, “Wi” is the multiplication of all associated weights in the hierarchy of “ith” factor ( as seen in Table 5) and “Ri” is a rating given for the defined class of the “ith” factor found on the assessed land unit

Learning Point:

- AHP will be an highly effective methodology for us to reduce the complexity in computing overall accessibility score by structurally factoring the pairwise comparisons of all facilities. Consistency Ratios need to be factor in too.

- Linear weighted combination of accessibility score could be adopted for our study

Caveat:

As this analysis is done on a proprietary software (ArcGIS 9.3), it is difficult for researchers to replicate the methodology of the research paper unless they have access to such software. As we aim to provide urban planners an open-source and easily reproducible application through R programming, there is a need to find similar packages for such methodology on R programming.

2.Estimating Spatial Accessibility to Facilities on the Regional Scale: an Extended Community-based Interaction Potential Model

Study Objective:

The study aims to leverage on measurements of spatial accessibility to regional facilities using aggregated data.The set of facilities includes three types of food outlets on the regional level at Bas-Rhin department,, namely hyper/supermarkets, grocery stores and bakeries.

Visualization:

Maps of number of grocery stores (left) and potential accessibility surface(right)

Methodology

1.Frequency Count of Opportunities within a Given Neighbourhood

Frequently used indices based on count was first illustrated to give users a quick overview of the spatial distribution of facilities. This is known as container index which overcomes the limitation of individuals choosing only the nearest facility for consumption and actually consider all available opportunities within a neighbourhood.

2. Community-based Interaction Potential Model

This model take into account of difference in urbanization level in the region when computing the accessibility level. As accessibility is a multi-dimensional concept, travel behaviours of the population are factored in. Kernel density estimation and Enhanced Two-Step Floating Catchment Area Method are used for accessibility assessment. These methods consider demand (population) and supply (health practitioners) side as well as travel impedance specification by assigning higher weight to opportunities in nearer region.

Learning Point:

1. Importance of Aggregating Data without consideration of administrative boundaries

To avoid administrative boundaries from limiting the number of closest facilities for each HDB units, administrative boundaries should be ignored when aggregating data. This is more realistic and precise estimation of accessibility levels such that we will not have areas with null accessibility.

2. Data Availability

To effectively implement such customized potential model for spatial accessibility analysis, we need demand, supply of facilities and household characteristics at each HDB units including travel impedance.

Caveat:

1. The study uses population of the region as the base reference to calculate the accessibility to the facilities. However, it failed to take into account of comparison with specific entities (such as HDB flats in our study).

2. The models developed in this study were implemented in the XLISP-STAT programming environment and ArcGIS 9.2 was used for the mapping visualizations. To adopt similar methodology, we need to ensure our programming language have similar functions.

Application Prototype

User Interface Prototype

Technical Challenge

Tools and Data Architecture

Challenges:

1. Most of the datasets retrieved provided only addresses, not coordinates. Thus, first we had to geocode each point to get the coordinates.

2. Some datasets had CRS WGS84 while some had SVY21. Thus, we had to convert all to SVY21

3. Calculating the distance from each of the 8500 houses to each of the 5000 bus stops was computationally impossible. Thus, we had to use Raster to create a radius around each house and calculate distance from that house to the bus stops which lay within the radius to get the closest bus stop

4. Plotting 8000 points on a map was very cluttered and not insightful. Thus, we provided the user options to select regions/subzones/towns for better plots

Related Work

1. https://www.researchgate.net/publication/242450034_A_GIS-BASED_MULTI-CRITERIA_ANALYSIS_APPROACH_TO_ACCESSIBILITY_ANALYSIS_FOR_HOUSING_DEVELOPMENT_IN_SINGAPORE/download
2. https://www.researchgate.net/publication/221354375_GIS-Based_Spatial_Distribution_and_Evolvement_Analysis_of_Urban_Affordable_Housing_A_Case_Study/download

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