Spatial Analysis Dissemination of Census Data United Nations

Spatial Analysis & Dissemination of Census Data United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Amman, Jordan, 16 -19 May, 2011

Outline n Geographic Database n Spatial Analysis Techniques n Examples United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Amman, Jordan, 16 -19 May, 2011

Geographic Database q Geographical features (Conceptual Model) n n n Components selection Attributes Structure q Spatial Relationships (explicit -Topolgy) United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Amman, Jordan, 16 -19 May, 2011

Spatial relationships q Logical connections between spatial objects represented by points, lines and polygons q e. g. , - point-in-polygon - line-line - polygon-polygon United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Amman, Jordan, 16 -19 May, 2011

Complete EA map with all components overlaid on one map display Main components are: Street network, Buildings EA boundaries layer Annotation, Symbols, Labels Building numbers Neatlines Legend United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Amman, Jordan, 16 -19 May, 2011

Spatial Operations q “adjacent to” q “connected to” q “near to” q “intersects with” q “within” q “overlaps” q etc. United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Amman, Jordan, 16 -19 May, 2011

Spatial Analysis Techniques q the main use of spatial analysis is for census products and services q Techniques include: queries, distance measurements, buffering, linear interpolation, point pattern analysis, and cartograms, etc. q All offer functionality beyond standard thematic 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 Amman, Jordan, 16 -19 May, 2011

Spatial Analysis: Query q select features by their attributes: n “find all districts with literacy rates < 60%” q select features by geographic relationships n “find all family planning clinics within this district” q combined attributes/geographic queries n “find all villages within 10 km 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 Amman, Jordan, 16 -19 May, 2011

Examples: What is at…? Features that meet a set of criteria United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Amman, Jordan, 16 -19 May, 2011

“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 Amman, Jordan, 16 -19 May, 2011

“is near to”: Buffer Operations • Point buffer • Affected area around a Hospital • Catchement area of a water source United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Amman, Jordan, 16 -19 May, 2011

“is near to”: Buffer Operations • Point buffer • Affected area around a polluting facility • Catchement area of a water source United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Amman, Jordan, 16 -19 May, 2011

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 Amman, Jordan, 16 -19 May, 2011

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 Amman, Jordan, 16 -19 May, 2011

Spatial Analysis Techniques q point-in-polygon analysis n n 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. q Polygon overlay analysis n n 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 Amman, Jordan, 16 -19 May, 2011

“ 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 Amman, Jordan, 16 -19 May, 2011

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 Amman, Jordan, 16 -19 May, 2011

Spatial aggregation q Example of Spatial aggregation: n fusion of many provinces constituting an economic region United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Amman, Jordan, 16 -19 May, 2011

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 12. 7 15. 9 26. 0 27. 2 24. 5 26. 1 United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Amman, Jordan, 16 -19 May, 2011

Example of linear interpolation creating contours United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Amman, Jordan, 16 -19 May, 2011

Spatial Analysis Techniques q Thiessen polygons n 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. n 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 Amman, Jordan, 16 -19 May, 2011

Areas of influence q Commuting distances: daily commuters flow United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Amman, Jordan, 16 -19 May, 2011

Modeling/Geoprocessing q modeling: identify or predict a process that has created or will create a certain spatial pattern n 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 Amman, Jordan, 16 -19 May, 2011

Modelling: smoothing q Evolution of the population beetwen two censuses United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Amman, Jordan, 16 -19 May, 2011

Spatial Analysis Techniques q Cartograms n sometimes used to display census results n 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 Amman, Jordan, 16 -19 May, 2011

Location-allocation problems q Site selection q Optimal allocation q Multicriteria Analysis United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Amman, Jordan, 16 -19 May, 2011

Conclusion q Geographic Database q Topology q 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. q Variety of techniques: buffering, overlay, modelling q GIS: Decision making tool United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Amman, Jordan, 16 -19 May, 2011

THANK YOU! United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Amman, Jordan, 16 -19 May, 2011