Spatial Analysis & Dissemination of Census Data An understanding of the spatial distribution of human activity provides valuable information on the analysis of settlement and neighborhood patterns and the distribution of residential, commercial, and industrial activities. It has been argued that social and spatial structure “feed upon one another” to, in a literal sense, eventually become each other. Knowing where the young and old live, tells us about the changing social relationships and their individual geographies. It is a basis for a better knowing of why society is organized as it is, making us to learn from history so that we properly plan. Dorling (1994) argues that spatial patterns of a population reflect the social structure. These patterns reflect a reality that impinges upon everyday lives; lives whose course is governed by that social structure, a social structure that is changing spatially. United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Nairobi, Kenya, 14-17 September, 2010 Outline Geographic Database Spatial Analysis Techniques Examples “Spatial analysis can offer the census new ways to investigate data. Sometimes the only connection between two phenomena is their location in space. GIS can be a tool for data mining and even creating new, unique information. Spatial methods like buffering, finding distance between items, phenomena that expand in space and density of characters in a spatial unit. These types of queries are the essence of GIS. First use of these methods was done in investigating the 1995 census data. The 2006 census can help to establish a new framework, making GIS methods a real, independent research tools for use in the publication of the national statistics” (Israel report). United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Nairobi, Kenya, 14-17 September, 2010 Geographic Database Geographical features (Conceptual Model) Components selection Attributes Structure Spatial Relationships (explicit -Topolgy) United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Spatial relationships Logical connections between spatial objects represented by points, lines and polygons e.g., - point-in-polygon - line-line - polygon-polygon Fundamental Questions addressed by GIS What is in a particular place? Find the position of some object What is the area of, the distance from specific object? Find patterns- by looking at the distribution of features on the map instead of just an individual feature Combination of data layers Point in polygon operation Line in polygon operation Polygon overlay United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010 4

Nairobi, Kenya, 14-17 September, 2010 Spatial Operations “adjacent to” “connected to” “near to” “intersects with” “within” “overlaps” etc. United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Spatial Analysis Techniques the main use of spatial analysis is for census products and services Techniques include: queries, distance measurements, buffering, linear interpolation, point pattern analysis, and cartograms, etc. All offer functionality beyond standard thematic (choropleth) mapping, with many tools now available in both commercial and open-source software programs. Although spatial analysis is sometimes used during the enumeration phase (clustering, for example, can aid in identifying housing units to be canvassed), the main use of spatial analysis is for census products and services. A variety of techniques including buffering, linear interpolation, point pattern analysis, and cartograms, offer functionality beyond standard thematic (choropleth) mapping, with many tools now available in both commercial and open-source software programs. United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Spatial Analysis: Query select features by their attributes: “find all districts with literacy rates < 60%” select features by geographic relationships “find all family planning clinics within this district” combined attributes/geographic queries “find all villages within 10km of a health facility that have high child mortality” Query operations are based on the SQL (Structured Query Language) concept United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Nairobi, Kenya, 14-17 September, 2010 Examples: What is at…? Features that meet a set of criteria United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Nairobi, Kenya, 14-17 September, 2010 “is nearest to” Point/point Which family planning clinic is closest to the village? Point/line Which road is nearest to the village Same with other combinations of spatial features United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

“is near to”: Buffer Operations Point buffer Affected area around a Hospital Catchment area of a water source United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

“is near to”: Buffer Operations Point buffer Affected area around a polluting facility Catchment area of a water source United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Nairobi, Kenya, 14-17 September, 2010 Buffer Operations Line buffer How many people live near the polluted river? What is the area impacted by highway noise? United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Nairobi, Kenya, 14-17 September, 2010 Buffer Operations Polygon buffer Area around a reservoir where development should not be permitted United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Spatial Analysis Techniques point-in-polygon analysis Determines whether a point lies inside or outside a polygon. Can be used to compare geo-coded village centroids lying inside and outside hazardous areas such as tropical storm tracks or earthquake zones. Polygon overlay analysis Involves comparison between the locations of two different polygonal data layers. For example, the boundaries of two administrative districts could be compared to troubleshoot errors in the field enumeration process United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

“ is within”: point in polygon Which of the cholera cases are within the containment area United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Nairobi, Kenya, 14-17 September, 2010 Problem: We may have a set of point coordinates representing clusters from a demographic survey and we would like to combine the survey information with data from the census that is available by enumeration areas. Solution: “Point-in-Polygon” operation will identify for each point the EA area into which it falls and will attach the census data to the attribute record of that survey point. United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Nairobi, Kenya, 14-17 September, 2010 Spatial aggregation Example of Spatial aggregation: fusion of many provinces constituting an economic region United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Spatial data transformation: interpolation Example 1: Based on a set of station precipitation surface estimates, we can create a raster surface that shows rainfall in the entire region 13.5 20.1 26.0 27.2 12.7 15.9 24.5 26.1 United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Nairobi, Kenya, 14-17 September, 2010 Example of linear interpolation creating contours Illustration showing how contour lines of elevation can be derived through linear interpolation from a satellite image. United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Thiessen polygons illustrated Spatial Analysis Techniques Thiessen polygons Have the unique property that each polygon contains only one input point (e.g. settlements), and any location within a polygon is closer to its associated point than to the point of any other polygon. This method assumes that the values of the unsampled data are equivalent to those of the sampled points. Thiessen polygons illustrated United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Nairobi, Kenya, 14-17 September, 2010 Areas of influence Commuting distances: daily commuters flow United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Modeling/Geoprocessing modeling: identify or predict a process that has created or will create a certain spatial pattern diffusion: how is the epidemic spreading in the province? interaction: where do people migrate to? what-if scenarios: if the dam is built, how many people will be displaced? United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Nairobi, Kenya, 14-17 September, 2010 Modelling: smoothing Evolution of the population beetwen two censuses United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Spatial Analysis Techniques Cartograms sometimes used to display census results The areas of the original polygons are expanded or contracted based on their attribute values such as population size or voting habits United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Location-allocation problems Site selection Optimal allocation Multicriteria Analysis United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Nairobi, Kenya, 14-17 September, 2010 THANK YOU! United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010