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Development and Use of Geographic Database and GIS for Census Data Dissemination

This seminar highlights the significance of geo-databases and GIS for efficient census data dissemination and spatial analysis. It emphasizes the continuous evolution of the census geography program and the integration of geospatial technologies at all census stages.

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Development and Use of Geographic Database and GIS for Census Data Dissemination

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  1. Development and Use of Geographic Database and GIS for Census Data Dissemination United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  2. Outline • Census Geography Programme • Census Cycle • Adminstrative Hierarchy • Geocoding System • Building a Geographic Database • The Power of Maps • Introduction and Example • Dynamic Census Atlases • Overview & Example • Digital Geographic Data for Dissemination • Overview & Cost and Benefits • Digital Data Dissemination Strategies and Users • Overview of Users United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  3. Census Geography Programme: a continuous process • The recommendations derived from UN EGM and Workshops on GIS and census mapping emphasized the need for countries to consider the census geography programme as a continuous process, rather than the sequential mapping and dissemination operations. • It was also emphasized that the use of and application of contemporary geospatial technologies and geographical databases is beneficial at all stages of population and housing census process. Geospatial improve the efficiency in the preparatory, enumeration, processing and dissemination phases of the census United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  4. Census Cycle United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  5. GIS with Census mapping at all stages Pre-census Census Post-Census (Pre-enumeration) (Enumeration) (Post-enumeration) GPS/PDA GIS Digital Mapping GPS Photo/Video GIS Digital Mapping Satellite Imagery GIS Internet (Map-Server) Administrative and Reporting Units EAs Units United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  6. Administrative hierarchy • Every country has its own specific administrative hierarchy • Definition: A system by which the country and each lower level set of administrative units (except the lowest) are subdivided to form the next lower level. • Administrative areas for which census data will be reported United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  7. Example of Administrative Hierarchy • for the purposes of the census a country may have been divided into seven hierarchical levels in urban areas and six in rural areas Generic census geographic hierarchy United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  8. Illustration of a nested admin.Hierarchy • Relationships among all types of administrative and reporting unit boundaries are defined. • hierarchical levels may have actual administrative roles • Other units may have statistical roles alone United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  9. Coding Scheme • A unique numeric code needs to be assigned to each enumeration area or administrative unit. • This is the numeric code that provides the link between the aggregated census data and the digital EA boundary database stored in a GIS. • Ideally the coding scheme needs to be determined on a country by country basis. United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  10. Coding Scheme • EA: a basic geographic feature • Need for an identifier: linking the geographic feature to the census data (attributes) recorded for them • EAs and administrative units: coding scheme • A unique code assigned to each EA, used in data processing • Coding scheme: scalability, flexibility, intuitiveness, compatibility • Example of a hierarchical coding scheme 1 2 0 3 2 4 4 0 1 2 0 0 5 Enumeration area district locality province United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  11. Enumeration Area (EA) • EAs are the operational geographic units for the collection of census data • Defined early in the census process. • Some facilitate census data collection while others pertain to the usefulness of EAs in producing output products • i.e., the relationship between data collection and tabulation units. • Delineation of EAs is similar whether manual or digital cartographic techniques are used. United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  12. Geocoding Concept • “Geocoding can be broadly defined as the assignment of a code to a geographic location. Usually however, Geocoding refers to a more specific assignment of geographic coordinates (latitude, longitude) to an individual address (UN Report of the EGM on Contemporary Practices in Census Mapping and Use of GIS, 2007) • Geo-coding: not limited to address-matching • Geocoding covers a continuum of spatial scales: from individual housing units to enumeration area level up to higher administrative or national levels. United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  13. Geodatabase Development • Scanning, georeferencing, and vectorization of existing paper maps to develop digital datasets; • Conversion of existing digital maps and datasets into the desired data structure; • Updating of digital datasets since the last census activity to ensure that new settlements and roads are included and obsolete settlements are omitted from the enumeration activities; and/or • Collection of aerial or satellite imagery followed by digital feature extraction and ground-truthing with GPS to ensure proper georeferencing of the images. United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  14. Components of a Hypothetical urban EA map United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  15. 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 Nairobi, Kenya, 14-17 September, 2010

  16. Implementation of an EA database • All large operational GISs are built on geodatabases; • Arguably the most important part of the GIS • Geodatabases form the basis for all queries, analysis, and decision-making. • A DBMS, or database management system, is where databases are stored. United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  17. Several types of data organization • Varieties of relational database and geodatabase structure • Database management systems (DBMSs) can be divided into various types, including: • Relational, • Object, • Object-relational United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  18. Example: the Relational Database Model • The relational database model is used to store, retrieve and manipulate tables of data that refer to the geographic features in the coordinate database. • It is based on the entity-relationship model • In a geographic context, an entity can be administrative or census units, or any other spatial feature for which characteristics will be compiled. United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  19. Entity-Relationship Example: EA entity can be linked to the entity crew leader area. The table for this entity could have attributes such as the name of the crew leader, the regional office responsible, contact information, and the crew leader code (CL code) as primary code, which is also present in the EA entity. R 1-1 1-N United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  20. Implementation of an EA database • : Example of an entity table – enumeration area United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  21. Example: Census GIS database United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010 • - Basic elements • Entity: administrative or census units • enumeration areas • Entity type / Relations • Components of a digital spatial census database: • Boundary database • Geographic attribute tables • Census data tables

  22. Components of a digital geographic census database United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  23. The power of maps • Maps communicate a concept or an idea. • Maps are often meant to support textual information • Maps appeal to the viewer’s curiosity • Maps summarize large amounts of information concisely • Maps can be used for description, exploration, confirmation, tabulation • Maps encourage comparisons: • Between different areas on the same map: where are population densities highest? • Between different maps: is child mortality higher in the districts of province A than in province B? • same area: where and by how much do literacy rates for males and females differ in the districts? • Between maps for different time periods: did fertility rates decline since the last census? United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  24. Dynamic census atlases • Alternative to a static census atlas • Publishing of a digital map and database together with mapping software can allow users to produce custom maps of census indicators. • Normally includes digital boundary files at a lower resolution than the full census database to allow fast drawing and low disk usage • closely integrated attribute table should contain only a selected number of census indicators. • Densities and ratios that are appropriate for mapping should already be calculated. United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  25. Dynamic census atlases • The data provider should therefore provide an easy-to-use package together with the boundaries and data. • The use of that package should require minimal training and experience. • The application should be “plug-and-play”—after installation, the user should immediately be able to produce maps • Drill-down options for different geographic selections • Interactive area delineation options (e.g. select schools in a district) United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  26. A screenshot of Ukraine’s dynamics census atlas United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  27. GIS capabilities: Visualization United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  28. Digital Geographic Data for Dissemination • Demand for digital databases that consist of extractions of the census agency’s digital geographic master database will only increase • Census data are an important input in policy planning and academic analysis in many fields. • Health service provision, educational resource allocation, design of utilities and infrastructure, and electoral planning are some applications where government agencies require spatially referenced small area population statistics. • Commercial users employ such data for marketing applications and location decisions. United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  29. Digital Geographic Data for Dissemination • Benefits and costs • Benefits: Unsurpassed detail and precision, the potential use of census data in numerous applications--especially when overlaid on other geographic data such as terrain, and the relative ease of management and storage of thousands of units • Costs:expense in processing and data management, possible data disclosure issues, and quality control; costs of metadata production should be factored into the equation as well United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  30. Digital Data Dissemination Users • The wide range of potential users of disaggregated census data means that the NSO needs to pursue a multi-leveled digital data dissemination strategy. • Broadly, we can distinguish between the following types of users: • Advanced GIS users • Computer literate users • Novice users United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  31. Cont… • Advanced GIS users • work easily with large datasets and can use ftp to access them • Require extensive metadata. Sometimes called data extractors or “power users” • They will want access to spatial and attribute information in a comprehensive digital geographic format • The census office needs to supply comprehensive documentation on the geographic parameters used for the geographic database as well as on the individual census variables • The spatial information will be distributed in an open geographic format that can be easily converted into any number of commercial GIS formats United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  32. Cont… • Computer literate users • Government, commercial or private sector users who want to be able to browse the thematic information in a census database spatially. • Want to produce thematic maps and thus need to be able to perform simple manipulation of cartographic parameters. • Simple analytical functions such as aggregation of census units to custom-designed regions should also be possible. • This group of users is best served with a comprehensive, pre-packaged application that is designed for a commercial or freely available desktop mapping package. • Documentation requirements are somewhat smaller, since the users are unlikely to change the geographic parameters of the database or perform more advanced GIS operations. United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  33. Cont… • Novice users • Largely want to view pre-prepared maps on a computer and perhaps perform some basic queries • Best data distribution strategy is often to produce a self-contained digital census atlas • This atlas could consists of a series of static map images, for example, in the form of a slide show • Or it could be a very simple mapping interface with pre-designed map views that allow basic queries • Both, static maps and a simple map interface, can be made accessible through the Internet United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  34. Server GIS • Data dissemination • Web map publishing • GIS Services (geocoding, gazetteer, etc.) • GeoVisualization tools United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  35. CHILE: HOUSING AND POPULATION CENSUS DISTRICTS 2002 United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  36. Tsunami Affected Areas in Gizo, Solomon Islands United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

  37. GIS Clients Web Browsers 3D GeoVisualization Tools Desktop GIS PDAs/MCDs Mobile Phones GIS Services Routing Geocoding Gazetteer Custom services Now many GIS Clients - Consuming GIS Services(Source: ESRI) United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

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

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