Table Of Content

ST/ESA/STAT/SER.F/79 Department of Economic and Social Affairs Statistics Division Studies in Methods Series F No. 79 Handbook on geographic information systems and digital mapping United Nations New York, 2000 - i - NOTE The designations used and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the United Nations concerning the legal status of any country, territory, city or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries. The term “country” as used in this publication also refers, as appropriate, to territories or areas. The designation “developed regions” and “developing regions” are intended for statistical convenience and do not necessarily express a judgment about the stage reached by a particular country or area in the development process. Symbols of United Nations documents are composed of capital letters combined with figures. Mention of such a symbol indicates a reference to a United Nations document. ______________________ ST/ESA/STAT/SER.F/79 UNITED NATIONS PUBLICATION SALES No. 00.XVII.12 ISBN 92-1-161-426-0 - i i- Preface The United Nations has, over the years, issued a b) support data collection and help monitor census series of handbooks and technical reports intended to activities during enumeration; and assist countries in planning and carrying out improved and cost-effective population and housing c) facilitate presentation, analysis and dissemination censuses. These handbooks and reports have been of census results, during the post-enumeration reviewed from time to time to reflect new phase. developments and emerging issues in census taking. The present handbook is part of a series of handbooks The publication is divided into three chapters. that have been developed to assist countries in their The structure reflects as closely as possible the census preparation for the 2000 and future rounds of cycle. The first chapter gives an introduction and censuses. The other handbooks in the series include: overview of geographic information systems and digital mapping. The second chapter discusses, inter (a) Handbook on Population and Housing Census alia, cost-benefit analysis of an investment in digital Editing (ST/ESA/STAT/SER.F/82); cartography and GIS, plans for census cartographic (b) Handbook on Census Management for Population process, digital map database development, quality and housing censuses (ST/ESA/STAT/SER.F/ assurance, database maintenance, and use of GIS 83). during census enumeration. The last chapter describes The Principles and Recommendations for the role of GIS and digital mapping in the post-censal Population and Housing Censuses – Revision 1 phase and deals with tasks after the census and during (United Nations, 1998) make reference to the the inter-censal period, such as database maintenance, emergence of new technologies for census dissemination of geographic census products, and operations. One of the new technologies is the geographic analysis of census data. application of geographic information systems (GIS) and digital mapping in censuses since technical The handbook is as comprehensive as possible developments in computer hardware and mapping without overloading the reader with too much software have already encouraged many statistical technical presentation, which is dealt with in the and census offices to move from traditional annexes. The annexes provide technical aspects such cartographic methods to digital mapping and as an overview of GIS, coordinate systems and map geographic information systems. projections, geographic data modelling, and thematic mapping. The purpose of this publication is to assist countries by providing a reference document that During the revision process, the United Nations focuses on digital mapping aspect when conducting Secretariat consulted cartographic and GIS experts population and housing censuses. Traditionally, the representing all regions of the world to review and role of maps in the census has been to support finalize the handbook. The handbook also presents, enumeration and to present aggregate census results some examples of country practices in the application in cartographic form. In addition to enabling more of GIS and digital mapping used in censuses efficient production of enumerator maps and thematic contributed by some of these experts. The present maps of census results, GIS now plays a key role in publication was drafted by Mr. Uwe Diechmann, a census data dissemination and in the analysis of consultant for the United Nations Statistics Division. population and household data. In particular, the objectives of the publication are to provide guidance to countries on how to: a) ensure consistency and facilitate census operations, particularly at the pre- enumeration phase; -i i i- -i v - Contents Chapter Page Abbreviations and acronyms......................................................................................................................viii I. Introduction and overview......................................................................................................................1 A. The role of maps in the census.............................................................................................................1 B. The mapping “revolution” ...................................................................................................................1 C. Increasing demand for local area statistical data..................................................................................2 D. Scope, purpose and outline of the handbook........................................................................................3 II. Pre-enumeration......................................................................................................................................5 A. Introduction..........................................................................................................................................5 B. Cost-benefit analysis of an investment in digital cartography/geographic...........................................5 1. Costs .......................................................................................................................................6 2. Benefits...................................................................................................................................10 (a) Efficiency benefits.....................................................................................................10 (b) Effectiveness benefits................................................................................................11 3. Critical success factors............................................................................................................13 C. Planning the census cartographic process..........................................................................................13 1. Overview................................................................................................................................13 2. Needs assessment and determination of mapping options.....................................................14 (a) User needs assessment...............................................................................................14 (b) Determination or output products..............................................................................15 (c) Mapping options........................................................................................................15 3. Institutional issues in setting up a digital mapping program.................................................16 (a) Staffing, responsibilities and training requirements...................................................16 (b) Institutional cooperation............................................................................................18 (c) Equipment and software for census mapping applications........................................20 (d) Decentralization of census mapping activities...........................................................25 (e) Timing of census mapping activities..........................................................................25 (f) Process control..........................................................................................................27 4. Definition of the national census geography..........................................................................27 (a) Administrative hierarchy............................................................................................27 (b) relationship between administrative and other statistical reporting or management units......................................................................................................28 (c) Delineation of enumeration areas...............................................................................29 (d) Delineation of supervisory (crew leader) areas..........................................................30 (e) Consistency with past censuses..................................................................................30 (f) Coding scheme...........................................................................................................30 5. Geographic information system database design....................................................................31 (a) Scope of mapping activities........................................................................................31 (b) Implementation choices..............................................................................................35 (c) Definition of the geographic information system database structure..........................36 (d) Metadata development................................................................................................40 (e) Data quality issues......................................................................................................41 (f) Tiling of national territory into operational zones.......................................................44 (g) The digital administrative base map...........................................................................44 (h) Dealing with disjoint area units..................................................................................44 (i) Computing areas.........................................................................................................45 - v - D. Digital map database development..........................................................................................................46 1. Overview........................................................................................................................................46 2. Cartographic data sources for enumeration area mapping (secondary data acquisition)................48 (a) Types of maps required...............................................................................................48 (b) Inventory of existing sources.....................................................................................49 (c) Importing existing digital data...................................................................................49 3. Additional geographic data collection (primary data acquisition)..................................................50 (a) Field techniques overview..........................................................................................50 (b) Global positioning systems.........................................................................................50 (c) Aerial photography.....................................................................................................55 (d) Satellite remote sensing..............................................................................................60 4. Geographic data conversion............................................................................................................63 (a) Conversion of hard-copy maps to digital data............................................................63 (b) Digitizing....................................................................................................................63 (c) Scanning.....................................................................................................................65 (d) Editing........................................................................................................................68 (e) Constructing topology................................................................................................68 5. Digital map integration...................................................................................................................69 (a) Introduction................................................................................................................69 (b) Georeferencing...........................................................................................................69 (c) Projection and datum change.....................................................................................70 (d) Coding.......................................................................................................................71 (e) Integration of separate map segments........................................................................71 E. Quality assurance, enumeration area map production and database maintenance...................................72 1. Overview........................................................................................................................................72 2. Draft map production and quality assurance procedures...............................................................73 (a) Matching boundaries and attribute files and printing overview maps........................73 (b) Quality assurance.......................................................................................................73 (c) Verification by local authorities and final administrative unit check.........................74 3. Enumeration area map printing......................................................................................................74 F. Use of geographic information systems during census enumeration......................................................78 1. Use of digital maps for census logistics..........................................................................................78 2. Monitoring progress of census operations......................................................................................78 3. Updating and correction of enumeration area maps during enumeration.......................................79 III. Post-enumeration 81 A. Introduction.............................................................................................................................................81 B. Tasks after the census and during the inter censal period.......................................................................81 1. Immediate tasks..............................................................................................................................81 (a) Incorporating updates and changes suggested by enumerators..................................81 (b) Reconciliation of collection units and tabulation or statistical units..........................81 2. Database maintenance.....................................................................................................................83 (a) Database archiving.....................................................................................................83 (b) Database maintenance: advantages of a continuous mapping program.....................83 C. Dissemination of geographic census products..........................................................................................83 1. Planning data dissemination...........................................................................................................83 2. Required products...........................................................................................................................84 (a) Equivalency and comparability files..........................................................................84 (b) Reference map library................................................................................................85 (c) Gazetteers and centroid files......................................................................................85 -v i- 3. Thematic maps for publication.......................................................................................................85 (a) The power of maps.....................................................................................................85 (b) Thematic mapping of census data..............................................................................86 (c) Thematic map production and publication issues......................................................87 (d) Output options...........................................................................................................88 4. Digital geographic databases for dissemination..............................................................................92 (a) Definition of data content..........................................................................................93 (b) Data formats..............................................................................................................93 (c) Documentation and data dictionaries.........................................................................95 (d) Preparation of deliverables........................................................................................96 (e) Legal and commercialization issues...........................................................................96 (f) Marketing of digital map products.............................................................................99 (g) Outreach...................................................................................................................100 5. Digital census atlases....................................................................................................................100 (a) Static census atlases...........................................................................................................100 (b) Dynamic census atlases.....................................................................................................101 6. Internet mapping...........................................................................................................................102 (a) Server-side approaches............................................................................................103 (b) Client-side approaches.............................................................................................104 (c) Hybrid approaches...................................................................................................104 (d) Opportunities for census data distribution...............................................................104 D. Advanced topics: geographic analysis of census data............................................................................106 1. Urban area definition/delineation.................................................................................................106 2. Reconciling small area statistics with similar information from previous censuses.....................106 (a) Aggregation of old enumeration areas to new district boundaries...........................107 (b) Areal interpolation where boundaries are incompatible..........................................108 (c) Temporal geographic information system databases...............................................112 3. Population data by grid cells.........................................................................................................112 Bibliography and references.........................................................................................................................115 Annex I. Geographic information systems..................................................................................................121 Annex II. Coordinate systems and map projections.....................................................................................133 Annex III. Data modelling............................................................................................................................145 Annex IV. Example of a data dictionary for distribution..............................................................................149 Annex V. Thematic map design...................................................................................................................153 Annex VI. Glossary......................................................................................................................................183 -v ii- Abbreviations and acronyms ASCII American Standard Code for GLONASS Global Navigation Satellite Information Interchange System BMP Bitmap GPS Global Positioning System BPS Bits per second HLS Hue lightness saturation BUCEN United States Bureau of the HPGL Hewlett-Packard graphics Census language CAD/CADD Computer-aided HTML Hypertext Markup Language design/Computer-Aided Design HVS Hue value saturation and Drafting ISO International Organization for CCD Charge-coupled device Standardization CD-ROM Compact disk-read only memory JPEG Joint Photographic Experts Group CGM Computer graphics metafile LAN Local Area Network CLA Crew leader area MB Megabyte CMY Cyan magenta yellow NSDI National spatial data infrastructure CMYK Cyan, magenta, yellow and black PDF Portable document format CSDGM Content Standards for Digital PES Post enumeration survey Geospatial Metadata RDBMS Relational database management DEM Digital elevation model system DGPS Differential global positioning RGB Red, green and blue system SPOT Satellite pour l'observation de la DHS Demographic and Health Survey terre DPI Dots per inch SQL Structured query language DVD Digital video/versatile disk TCP Transmission Control Protocol DXF Drawing exchange format TIFF Tagged image file format EA Enumeration area UPS Uninterruptable power supply ED Enumeration district UTM Universal Transverse Mercator ESRI Environmental Systems Research VPF Vector product format Institute WMF Windows metafile GB Gigabyte WWW World Wide Web GIF Graphics interchange file GIS Geographic information system v- i i-i Handbook on geographic information systems and digital mapping 1 I. Introduction and Overview A. The role of maps in the census • Maps make it easier to present, analyse and disseminate census results (post-enumeration). 1.1. Many of the changes to the Principles and Cartographic presentation of census results Recommendations for Population and Housing provides a powerful means for visualizing the Censuses (United Nations, 1998) reflect the emergence results of a census. This supports the identification of new technologies for census operations. Significant of local patterns of important demographic and technical developments will undoubtedly benefit census social indicators. Maps are thus an integral part of data capture, processing and distribution. In the policy analysis in the public and private sectors. cartographic domain, advances in computer hardware 1.4. The remaining sections of the introduction will and mapping software have already encouraged many provide a brief overview of the objectives of the statistical and census offices to move from traditional handbook. The following section summarizes the rapid cartographic methods to digital mapping and geographic developments in digital mapping that have also been the information systems (GIS) (see, e.g., Rhind, 1991; Ben- motivation for preparing the present handbook; the next Moshe, 1997; and United Nations, 1997a). section discusses why census offices are under 1.2. Traditionally, the role of maps in the census has increasing pressure to provide timely census data in been to support enumeration and to present aggregate geographically referenced form. Finally, the contents of census results in cartographic form. Cartographic the handbook are summarized in brief. automation has greatly expanded this role. In addition to enabling more efficient production of enumerator maps B. The mapping “revolution” and thematic maps of census results, GIS now plays a key role in census data dissemination and in the analysis 1.5. People have used maps for centuries to represent of population and household data. their environment. Maps are used to show locations, distances, directions and the size of areas. Maps also 1.3. Mapping has been an integral part of census taking display geographic relationships, differences, clusters for a long time. Very few enumerations during the last and patterns. Maps are used for navigation, exploration, several census rounds were executed without the help of illustration and communication in the public and private detailed maps. In general terms, digital mapping serves sectors. Nearly every area of scientific enquiry uses several purposes in the census process: maps in some form or another. Maps, in short, are an • Maps ensure consistency and facilitate census indispensable tool for many aspects of professional and operations (pre-enumeration). academic work. The census office needs to ensure that every 1.6. Cartography has been affected by the information household and person in the country is counted, and revolution somewhat later than other fields. Early that no households or individuals are counted twice. computers were good at storing numbers and text. For this purpose, census geographers partition the Maps, in contrast, are complex, and digital mapping national territory into small reporting units. Maps requires large data storage capacity and fast computing thus provide an essential control device that resources. Furthermore, mapping is fundamentally a guarantees consistency and accuracy of the census. graphical application, and early computers had limited • Maps support data collection and can help monitor graphical output capabilities. The earliest mapping census activities (during enumeration). applications implemented on computers in the 1960s did During the census, maps ensure that enumerators not therefore find wide application beyond a few can easily identify their assigned set of households. government and academic projects. It took until the Maps are also issued to census supervisors to 1980s for commercial geographic information systems support planning and control tasks. Maps can thus to reach a level of capability that would lead to their also play a role in monitoring the progress of rapid adoption, for example, in local and regional census operations. This allows supervisors to government, urban planning, environmental agencies, identify problem areas and implement remedial mineral exploration, the utility sectors and commercial action quickly. marketing and real estate firms. Handbook on geographic information systems and digital mapping 2 1.7. GIS has benefited greatly from developments in Digital techniques allow better management, faster various fields of computing. Better database software retrieval and improved presentation of such data. There allows the management of vast amounts of information has, therefore, always been a close linkage between that is referenced to digital maps. Computer graphics geography and statistics—as reflected, for instance, by techniques provide the data models for storage, retrieval the fact that the national statistical and mapping and display of geographic objects. Advanced agencies in many Latin American countries are housed visualization techniques allow us to create increasingly under the same roof (see, also, EUROSTAT, 1996). sophisticated representations of our environment. GIS This close integration of GIS in statistical applications data display functions go far beyond static two- yields large benefits to national statistical offices as it dimensional displays and provide animation and three- reduces the cost and time required to collect, compile dimensional modelling capabilities. Just as the input of and distribute information. GIS allows the statistical textual information is facilitated by optical character office to produce a greater number of services, thereby recognition, fast, high-resolution scanning and considerably increasing the return on investment in data sophisticated software speed up map data conversion collection. that previously relied exclusively on manual digitizing. 1.8. New information sources also shorten the time from C. Increasing demand for local area project planning to operational database. The most statistical data important recent developments have been in navigation 1.12. The benefits of geographic data automation in and remote sensing. The Global Positioning System statistics are shared by the users of census and survey (GPS) has revolutionized field data collection in areas data. The data integration functions provided by GIS, ranging from surveying to environmental monitoring which allow the linking of information from many and transportation management. A new generation of different subject areas, have led to a much wider use of commercial, high-resolution satellites promise pictures statistical information. This, in turn, has increased the of nearly any part of the earth's surface with enough pressure on statistical offices to produce high-quality detail to support numerous mapping applications. The spatially referenced information for small geographic cost of precision digital mapping will fall significantly units. The types of applications for such data are almost as a result of the close integration of GPS techniques limitless. Some examples are: and digital cameras in aerial photography. • Planning of social and educational services. A 1.9. Similar advances are occurring in the areas of main task of local and regional government is to geographic data dissemination. All major GIS vendors ensure that all parts of the country have equal now provide the tools to make geographical databases access to government services such as health care accessible via the Internet on the World Wide Web and education. Small area census data on age and (www). Government agencies at all levels are social characteristics allow planners to forecast embracing this technology to provide access to vast demand for various services. In combination with amounts of spatial information to the public cheaply and GIS data on transport infrastructure, this quickly. The Internet is likely to replace printed maps information allows better distribution of resources and digital media as the most important means of data among existing service centres and more rational distribution. decisions concerning the location of new facilities. 1.10. Internet mapping programs are one indication • Poverty analysis. In countries where income or that the tools to utilize digital spatial information are consumption data are not collected during a census, constantly becoming cheaper and easier to use. While household characteristics are an important indicator high-end GIS packages still require considerable of the welfare of various population groups. Small training to be used effectively, desktop mapping area census data, in combination with spatially packages are no more complicated to use than standard referenced information on infrastructure and agro- business software. Digital mapping is also becoming ecological conditions, can be used to estimate more closely integrated in standard computer poverty incidence and the location of poor applications such as spreadsheet, graphics and business communities. This information improves targeting management software. of poverty alleviation schemes by channelling resources to areas of greatest need while avoiding 1.11. Statistical offices were some of the early leakage of subsidies to non-poor communities. adopters of GIS. Population, social and economic statistics are the foundation of public planning and • Utility service planning. Private and public water, management. The spatial distribution of socio-economic gas, electricity and telecommunications utilities not indicators guides policy decisions on regional only use GIS to manage their physical development, service provision and many other areas. infrastructure, they also use spatial analysis of