Nairobi, Kenya, 14-17 September, 2010 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

Nairobi, Kenya, 14-17 September, 2010 Outline UN Recommendations/Census Geography Programme Building a Geographic Database Digital Data Dissemination Strategies and Users SALB Project Handbook on Geospatial Infrastructure in Support of Census Activities United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

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

Nairobi, Kenya, 14-17 September, 2010 Census Cycle Mapping is one of the most critical activities of a census. The accuracy of the delineation of enumeration areas and the quality of their representation on a map have a crucial impact on the quality of the data collected. The increasing use of hand-held devices with GPS, and low-cost aerial and satellite imagery for spatial data collection and demarcation of statistical enumeration areas, as well as GIS for display of census information, have improved census mapping in fundamental ways. Geographic data are now more easily collected, disseminated, accessed and manipulated by multiple providers and users. The three main operational phases of any National Statistics Office (NSO) can be supported by GIS: integrating field data collection; processing of statistical data, disseminating data and supporting statistical surveys using maps that can be made available through the web for wide public access (Figure 1). United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

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) Now, if we look at the use of these geospatial technologies with census mapping operations: We observe that GPS, Satellite Imagery and in particular GIS are supporting census mapping activities at all three stages. In terms of geographic units, which are essential components in GIS, the transition from pre-enumeration stage to enumeration requires the use of Enumeration Areas Units, and the transition from Enumeration stage to Post-enumeration stage requires administrative and reporting units. Administrative and Reporting Units EAs Units United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

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 Every country has its own specific administrative hierarchy, that is, 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. United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

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 The Figure exposed illustrates the nesting of administrative and census units using a simple example with only four hierarchical levels. Only some of these hierarchical levels may have actual administrative roles; for example, the province, district and locality levels may have capitals with local government offices that are responsible for those regions. Other units may have statistical roles alone; that is, they are designed for the display of data and not for administering territory. In some instances, however, administrative units may not be completely nested. Especially when considering both administrative and other statistical reporting units, the census office may need to deal with a very complex system of geographic regions. United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Nairobi, Kenya, 14-17 September, 2010 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 - A digital geographic database in vector format consists of a structured set of points, lines and polygones. Each geographic feature has a unique identifier which is used by the system internally (not accessible by the user and should not be modified externally). -Needed is a more meaningful identifier that can be used to link the geographic features to the attributes recorded for them. - For the EAs and administrative and administrative units this link is the unique EA (or administrative) identifier which is listed in the master file of all geographic areas relevant in the census. - Indeed, a unique code needs to be assigned to each EA. This code is used in data processing to compile enumerated information for households in each EA and aggregate this information for administrative or statistical zones for publication This is the numeric code that provides the link between the aggregated census data and the digital EA boundary database stored in a GIS. The most important guiding principles when designing a coding scheme are flexibility, expandability, intuitiveness, and compatibility with other coding schemes in use in the country. The NSO is often the custodian of coding schemes in the country and should also be the focal point for the design of the census mapping codes. For example a country could use the following coding scheme: The unique identifier for each smallest level unit – the EA- then consists simply of the concatenated identifiers of the administrative units into which it falls. An EA code of N 1 2 3 4 1 2 5 2 4 province district locality Enumeration area United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Nairobi, Kenya, 14-17 September, 2010 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. The relationship between geography and databases occurs through the mechanism of coding. The concept of geographic coding or “geocoding” goes beyond what is conventionally understood by the GIS industry to mean address-matching. The UN definition of “geocoding” is more broad, representing the connection between statistical observations and real-world locations expressed in terms of latitude and longitude or other locational attributes (in other words, geocoding is a way to ensure the data know where they are!) United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

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 Components of a hypothetical urban EA map. All features are stored in separate map layers in the same spatial reference system or as graphics templates. The main components are the street network, buildings and EA boundaries layer. In addition, annotation, symbols, labels and building numbers are stored in separate data layers, although these could also be added dynamically. The last component is a template consisting of neatlines (a box marking the outward extent of the map) and a legend which is consistently used for all EAs. In many countries that are not fully digital for the upcoming census round, EA map design may be simpler than in this example. For example, instead of a fully integrated digital base map in vector format, rasterized images of topographic maps may be used as a backdrop for EA boundaries. In some instances, map features may be more generalized, for instance by using only the centerlines for the streets and polygons for entire city blocks rather than for individual houses. United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Components of a Hypothetical urban EA map Components of a hypothetical urban EA map. All features are stored in separate map layers in the same spatial reference system or as graphics templates. The main components are the street network, buildings and EA boundaries layer. In addition, annotation, symbols, labels and building numbers are stored in separate data layers, although these could also be added dynamically. The last component is a template consisting of neatlines (a box marking the outward extent of the map) and a legend which is consistently used for all EAs. United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

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. All large operational GISs are built on geodatabases; they are 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. Through constructing a geodatabase, the NSO begins to realize the benefits of organizing itself around a geographic model. For designing census data models, an NSO must consider needs of its data users as well as statutory and constitutional provisions for census work. Generally a conceptual model can be developed to link basic collection geography from the enumeration, layers such as EAs, physical features (including elevation, slope, and aspect) and other layers that affect census-taking including point and area features such as landmarks. Vector topology has been mentioned in the previous section as playing a key role particularly in boundary and administrative area delineation. United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

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 EA EA-code Area Pop. Crew leader area CL-code Name RO responsible 1-1 1-N United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Implementation of an EA database : Example of an entity table – enumeration area In a geographic context, an entity can be administrative or census units, or any other spatial feature for which characteristics will be compiled. For example, an entity might represent the feature “enumeration area” (Figure III.17). Individual enumeration areas in a district or country are instances of this entity and will be represented as rows in the entity’s table. The entity type, in contrast, refers to the structure of the database table: the attributes of the entity which are stored in the columns of the table. For an enumeration area this may be the unique identifier, surface area, population, the code of the crew leader (CL) area that the EA is assigned to, and so on. Note that the entity type only refers to the generic definition of the database table, not to the actual values recorded for each instance. One or more attributes (columns) in the entity type are used as keys or identifiers. One of those is the primary key which serves as the unique identifier for an entity type. For an enumeration area database this would be the EA code. United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

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

Different Geographies A geography for data collection: EA level or even dwelling level Another geography for data dissemination: Aggregated level (confidentiality) United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Uses of Graphs: Enriching the Understanding of GIS Data Sets Exploratory Spatial Data Analysis Linked Maps, Graphs & Tables Dynamic Feature Selection Animation Visualization over Time United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

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

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 NSOs should consider costs and benefits of wider data dissemination when planning its products and services. United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

The Second Administrative Level Boundaries data set project (SALB) The Second Administrative Level Boundaries data set project (SALB) has been launched in 2001 in the context of the activities of the UN Geographic Information Working Group (UNGIWG) and has for objective to provide access to a working platform for the collection, management, visualization and sharing of sub national data and information in a seamless way from the national to the global level. unsalb.org  United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Nairobi, Kenya, 14-17 September, 2010 Handbook on Geospatial Infrastructure in Support of Census Activities (2009) http://unstats.un.org/unsd/demographic/standmeth/handbooks/default.htm United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis Nairobi, Kenya, 14-17 September, 2010

Nairobi, Kenya, 14-17 September, 2010 Conclusions Consider the Census Geography Programme as a continous process Adapt best practices to suit specific census requirements Partner with other stakeholders (the public and private sector) in order to Build the NSDI Work jointly on coding efforts Produce value added products – higher demand for census data 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