Symposium 2001/08

13 July 2001


                                                                                                           English only


Symposium on Global Review of 2000 Round of

Population and Housing Censuses: 

Mid-Decade Assessment and Future Prospects

Statistics Division

Department of Economic and Social Affairs

United Nations Secretariat

New York, 7-10 August 2001












Mapping for the 2000 round of censuses:

Issues and possible solutions *

Raj R. Tripathi **




Summary. 2

A. Introduction. 2

B. Cartography units and services. 2

C. Inadequacies of base maps. 4

D. Delays in execution of the pre-enumeration mapping programme. 6

E. Incomplete mapping coverage. 8

F. Deficient enumeration frame. 9

G. Deficiencies in the national master sampling frame. 12

H. Automated mapping and gis applications. 14

I. Outsourcing of gis and mapping activities. 16

J. Post-enumeration mapping programme. 17



Mapping for the 2000 Round of Censuses: Issues and Possible Solutions

Census-mapping activities have undergone considerable changes during the last three decades, particularly in the areas of the Geographic Information System (GIS), digital remote sensing and Global Positioning System (GPS). Some developing countries have established permanent cartography units in their census organizations, but most still lack the expertise and resources to take advantage of the new technology or even to produce adequate base maps for census enumeration. Topographic maps based on aerial photography are often out of date or unavailable. In countries where population growth is high and mobility is common, outdated maps do not necessarily reflect demographic changes. Moreover, many countries begin their censuses with maps produced for the previous census, which were compiled before GPS in field-mapping operations permitted accurate determination of boundaries and features.  Therefore, the existing base maps are only marginally useful for the current census.


Census organizations are expected to assess the gaps and deficiencies in their available base maps early in the planning process and decide how to update and revise maps. This may involve aerial photography, field mapping, high-resolution satellite data, or other sources, and the census office cooperates with other government departments that also use maps. Common errors in the mapping phase of the census are failing to allocate adequate resources, underestimating the time required for cartographic operations and lack of trained staff and equipment. Typically, some areas cannot be mapped in the field, including areas where access is denied, where terrain is difficult, where natural calamities have occurred, and where civil conflicts are under way.


Criteria for the demarcation of enumeration areas (EAs) include comparability with past censuses; capacity to produce small-area data and data for various administrative and statistical subdivisions; suitability for sample surveys; usefulness in data dissemination and analysis; compatibility with GIS database and applications; and identifiable boundaries and compactness of shape. Inevitably, these criteria cannot always be met, and EA maps may have ambiguous boundaries because of unstable features like tracks or footpaths. They may include only built-up areas, leaving farmland unaccounted for. Some EAs may be too big for one team to enumerate, they may have unusual shapes or they may have non-standard place names.


Area frames used for household sample surveys are usually drawn from the enumeration frames created for the census, so shortcomings in the census frame affect the accuracy of subsequent surveys. The census frame must be updated and reconciled by incorporating all changes that occurred between the cartographic fieldwork and the enumeration reference date. Some EAs may have been created during enumeration; they include new built-up areas; areas inhabited by mobile populations; isolated areas not previously accessed; and EAs with such institutions as hospitals or army barracks. Any changes in boundaries, spelling of place names and new features must also be incorporated into the census frame. The EAs must be identifiable on the ground in an unambiguous way, because different survey enumerators will use them at different times.


Many statistical offices have used automated mapping for production of maps for publication, but only a few countries so far have produced enumeration maps using computerized mapping systems. Rapid advances in digital mapping and GIS have led some countries to develop comprehensive GIS databases; this is a long-term activity and may be undertaken together with other national stakeholders and potential GIS data. It may also be useful to involve private companies in the more technical aspects of setting up the GIS system. Mapping activity in the post-enumeration phase includes continuous updating of maps and the GIS database, producing thematic maps and census atlases and educating data users on the utility of maps.

A. Introduction

1.                  Prior to the commencement of the 2000 census round, a majority of the countries had already conducted at least one or more scientifically-based population censuses. Therefore, for planning and implementation of cartographic preparations for the current round of censuses where censuses had already been held or were scheduled to be held soon, statistical offices had the strategic advantage of utilizing not only the accumulated knowledge base inherited from the past but also the immense treasure of maps and materials acquired and produced during the preceding censuses.


2.                  Over the period of the last three decades of census taking, census-mapping activities have undergone considerable changes and improvements in terms of concepts and procedures. Rapid advancements made in the disciplines of Geographic Information System (GIS), digital remote sensing and Global Positioning System (GPS) during the past decade have also greatly contributed to the process of improvement in most of the countries, though at variable levels.


3.                  Despite solid backing of operational experience and availability of census base maps and resource materials, implementation of cartographic activities for the current census round has been fraught with numerous and varied challenges and problems emanating mostly from resource scarcities, greater adoption of technology-driven procedures and the growing user requirements. The subsequent sections of this paper provide an overview of the main issues that posed problems in implementation of mapping activities and the corrective measures and strategies adopted by national statistical offices to resolve them. These issues and problems are typically relevant to all the developing countries.

B. Cartography units and services

4.                  To ensure timely production of various census maps of specified qualitative standards and to satisfy other cartographic needs as well, national statistical offices in most countries have established viable and self-contained cartography units and services. Continued support provided by the United Nations Population Fund (UNFPA) with multiple donor partnerships during the past three decades has played a vital role in building such capacities at national levels.


5.                  But in several countries these units are still not maintained on a continuous basis due mainly to inadequacies of financial and material resources coupled with lack of an established ongoing census-mapping programme. In these countries cartography services are revitalized and expanded to their full extent only at the time of undertaking pre-enumeration mapping activities and soon thereafter reduced to minimal core functions or even made virtually defunct for rest of the census cycle. In a few countries they become practically non-existent after census enumeration as staff deployed to cartographic activities are mobilized back to their original assignments. This state of periodic animation has resulted in not only the degradation of technical capacities but also the loss or misplacement of maps and records created or procured for the previous censuses due to lack of proper maintenance.


6.                  In the past in some countries where national statistical offices did not have necessary technical capacities to produce census maps, the tasks of census mapping were assigned to national mapping agencies. However, such arrangements encountered several problems and proved impractical due mainly to lack of requisite practical experience and low priority given to census work by these agencies.


7.                  Thus, for the 2000 round of censuses, cartography units in most of the countries had to be revived and in a few cases even set up from the scratch. It obviously took time for these units to become fully functional and embark on the census preparatory activities. The other factors that seem to have adversely affected the viability and technical capacities of cartography units are as follows:


·        High staff turnover due to lack of career opportunities for cartography staff in the national statistical services;


·        Further depletion of technical capacities developed in the past due to the high mortality rate among civil servants caused by the high prevalence of HIV/ AIDS in certain regions; and


·        Lack of adequately qualified personnel to fill positions in cartography units.


8.                  The combined effect of these factors has been the lack of experienced and adequately qualified cartography staff to undertake the census mapping and complete it on a timely basis. Necessary remedial measures taken in certain countries and other proposed strategies to redress staff inadequacies or shortfalls in the technical capacities are as follows:


·        Formulation of a comprehensive cartography programme covering both the pre-enumeration and the post-enumeration phases including continuation of certain long-term activities during the intercensal phase and accordingly making provisions for requisite resources in the census budget right at the outset;


·        Inclusion of a cartography component in the budget as well as a work programme of individual sample surveys and other data-collection activities to support the continuation of mapping activities leading to the production of adequately detailed and up-to-date maps needed for survey enumeration;


·        Mainstreaming of cartography staff into the regular cadres of national statistical and civil service staff in order to provide them career opportunities equal to those in other categories of statistical and civil service staff;


·        Secondment of suitably qualified and experienced cartography staff from other government departments or mapping agencies on a long-term or part-time basis. Such arrangements can also help in providing on-the-job training to census cartography staff in a cost-effective manner; and


·        Obtaining cartography staff through national technical cooperation mechanisms from the neighbouring countries where census mapping has already been done. 

C. Inadequacies of base maps

9.                  Maps needed for the census are usually compiled from various secondary resource maps and materials produced by the national mapping agencies, other government departments and international agencies. Availability of appropriate base maps and resource materials at affordable costs is therefore crucial to successful implementation of the census-mapping programme and attainment of desired quality standards in the final outputs.


10.              Lack of appropriate rural and urban base maps and materials still poses a serious constraint, more particularly in developing countries. The main deficiencies noticed in the available base maps are as follows:


·        Topographic maps produced by national mapping agencies, which constitute the main resource base for census mapping, are outdated, as the aerial photography used for their compilation often dates as far back as the1980s in most of the countries;


·        Lack of countrywide base map coverage on adequate scales poses yet another serious problem. Topographic maps on 1:50,000 scale that are widely used as rural base maps do not provide coverage to total geographical space in several countries. Photographic enlargements produced from 1:250,000 or other smaller-scale maps for use as substitutes have not proved useful due to the scantiness of the contents and problems of edge-matching between adjoining maps;


·        In many countries topographic maps are either out of stock or available in limited quantities. Production of reprints is often not possible because transparencies or repro-materials used for their printing are located outside the country;


·        Administrative divisions in most of the countries have undergone considerable changes during the post-independence period but these changes have not been incorporated into the existing maps;


·        Similarly, information pertaining to population and settlements and related sociocultural features shown on these maps has also become obsolete. Population size and distribution patterns in most of the countries have undergone considerable changes due to migration and other involuntary large-scale movements induced by resettlement programmes, natural calamities like floods and conflict situations;


·        Transportation networks (e.g., roads, tracks and footpaths), which are often used to define and establish boundaries of Enumeration Areas (EAs), and the grass-roots social structures have also become outdated in most of the areas, particularly those characterized by high population density;


·        Incorrectly spelled names of the localities, places, features and so forth;


·        Cartographic parameters (like spheroid, map datum, grid/graticule and so on) applied to construction of these maps in some countries do not fully match those adopted in the new technologies (GIS and GPS). This makes the tasks of base-map updating  and creation of digital map databases more complex and requiring more resources;


·        New built-up areas and squatter settlements are often not shown on most of the available urban layout maps; and


·        Unrealistically defined outer limits of certain towns with built-up areas extending beyond the officially notified limits or over ambitiously defined town limits encompassing large chunks of adjoining rural territories.


11.              The above-mentioned shortfalls have necessitated launching of intensive field-mapping exercises for the current round of censuses in most countries. They aim at upgrading the existing base maps, creating new maps for the areas not covered by base maps of required format and scale and gathering baseline information on counts of population and households for delineation and revision of EAs. Collection of georeferenced data in respect of outdated as well as newly emerged geographical features, boundaries, places, prominent locations, etc. has been done using Global Positioning System in most of the situations. The need to collect precisely accurate georeferenced data has also arisen to satisfy the requirements of GIS database development, which a majority of countries have embarked upon to automate the census-map production procedures.


12.              Extensive field-mapping exercises were also carried out in most of the countries for the preceding round of censuses, but locations of features and boundaries on the base maps could not be precisely determined at that time due to adoption of crude techniques and procedures of base map data collection and updating. Therefore base maps produced for the last census have not been very useful for the current round in most of the cases.


13.               Some good practices and strategies adopted in certain countries to effectively plan and implement the field updating and use of other appropriate materials for more dynamic and densely populated areas are listed below for reference and emulation elsewhere.


·        Making qualitative assessment of the gaps and deficiencies in the available base maps well ahead of time and accordingly formulating suitable cost-effective strategies for the updating and revision of base maps;


·        Using recent aerial photography, if available at other departments, to revise and update existing base maps or prepare new maps. Such revisions should preferably be undertaken in collaboration with the surveys department, as census offices usually do not have requisite expertise and equipment;


·        Systematic planning and implementation of field mapping to collect georeferenced data in respect of outdated and new features, places and boundaries using the new technology of Global Positioning System (GPS), more specifically for the rural areas;


·        Proper training of field staff in the use of field equipment and suggested procedures and methodologies to assure achievement of prescribed accuracy standards;


·        Acquisition of low-altitude photography or videography for the densely populated urban squatter settlements, new townships, built-up areas and areas of high population concentration for which up-to-date maps usually are not available. New technological advancements in the area of digital photography and image processing have opened the possibilities of acquiring and using such materials in a cost-effective manner. Such data acquisitions can be made more affordable by involving other partners to share costs and products; and


·        In countries with adequate resources, it is advisable to procure high-resolution satellite data for countrywide coverage, which then should be overlaid with boundaries of administrative divisions and other areas included in the census data-collection frame. Associated and other relevant descriptive data for the production of various enumeration maps should also be included.

D. Delays in execution of the pre-enumeration mapping programme

14.              The census is characteristically a time-bound operation and so are the cartographic activities to produce relevant maps needed for planning and implementation of various census programmes undertaken during its different phases. The resources and efforts spent on implementation of census mapping may not be fully justified if the relevant maps of prescribed standards and specifications are not produced and made available for use in time. This is truer in respect of enumeration maps, which are produced during the pre-enumeration phase. Usually it is recommended that all the maps needed for the field organization and conduct of the census enumeration must be produced at least a month before the census reference date so that they may be packaged along with other census materials (questionnaires, manuals, etc.) and dispatched to field offices.


15.              The pre-enumeration mapping programme is usually planned and implemented as a separate project in almost all countries because of its operational magnitude and the  enormous amount of resources required for its execution. This means that it should start well ahead of the actual census reference date and should involve a large number of regular as well as temporary census staff. The success of the census in terms of enumeration coverage and data quality largely depends on the quality of cartographic preparations, so it is imperative that the entire pre-enumeration mapping operation be planned and implemented in a very consistent and timely manner.


16.              The main activities that are implemented in most of the countries during the pre-enumeration phase for the production of various enumeration maps include field mapping, in-office processing of base maps and the map database and processing and production of enumeration maps. All these activities are operationally interlinked so that delays in implementation of one would cause a forward shift in the implementation schedules of all other subsequent activities. Of all the mapping activities accomplished during the pre-enumeration phase, field mapping is the most extensive as well as the most expensive and time-consuming. It usually covers updating of base maps, collection of geographic data for new features and delineation of EAs. Proper planning and timely implementation of this activity is therefore very crucial.


17.              To justify the huge investments involved, the strategies of the pre-enumeration mapping programme in most countries have been designed to produce the cartography outputs suitable not only for the census enumeration but also for the operational requirements of other data-collection activities and other user applications such as demarcation of electoral boundaries, defining catchment areas of various public services and so on. Production of maps meeting these requirements obviously takes time.


18.              Implementation of pre-enumeration cartographic activities including production of enumeration maps has experienced delays in most countries. The reasons that can be apparently attributed to these delays are the late start and slower progress than anticipated. This has often necessitated adoption of quick and shortened procedures resulting in compromises with the quality of final outputs. The main factors causing these delays are listed below:


·        Unrealistic assessment of time and resources required for the preliminary preparatory activities such as recruitment, training and mobilization of personnel, procurement of equipment, preparation and production of training and reference manuals, data-collection forms, etc. These activities are usually undertaken soon before commencement of field mapping, but time taken for their completion often exceeds the targeted timeline causing postponement of field operations;


·        Staff deployed on field mapping are not provided with adequate practical training on field procedures and use of equipment in actual terrain conditions. Such shortfalls in training prevent not only the mapping staff from thoroughly learning and rehearsing the field-mapping procedures but also the supervisors from making a proper assessment of the capabilities of individual staff deployed to work under them. This results in collection of inaccurate and incomplete data necessitating frequent revisits and callbacks to rectify the errors. Complete revision of work is sometimes necessary, thereby slowing down the pace of work and delaying completion of the field-mapping operations;


·        Inadequate and disrupted supply of field materials and logistics;


·        Poor maintenance of field equipment, particularly vehicles, resulting in frequent breakdowns and suspension of fieldwork;


·        Lack of support from local or traditional chiefs due to absence of publicity; and


·        Failure in implementing quality control measures including field inspection trips by senior cartographic staff to verify completed outputs and assess the performance rate of individual staff, especially in the early stages.


19.              Based on the assessment and evaluation of delays in certain countries where the pre-enumeration mapping activities for the current census round have already been implemented, the following remedial measures are recommended to avoid similar difficulties in other countries:


·        Thorough assessment of the field-mapping requirements for different parts of the country based on the quality of available resource maps and materials, settlement patterns and population size. Formal urban and rural settlements and areas for which recent aerial photographs or satellite images are available may not need intensive field mapping and therefore a less demanding strategy may be planned for these areas so as to allow more time as well as resources for other areas;


·        Soliciting support and involvement of local administration and heads of traditional social structures in verifying the boundaries of smaller areas and obtaining population estimates for EA delineation;


·        Determining the progress rates in terms of units of the stipulated output to be produced every week by each team or individual staff and making all involved in the execution of the mapping project aware of these rates;


·        Motivating field staff to work faster by providing additional incentives to those delivering more outputs and achieving better quality standards. Linking payment of  field allowances to delivery of output of stipulated quality; and


·        Periodic review of progress against the implementation schedule and effecting other quality control measures. Bridging any gap noticed in progress by instructing the concerned staff to work extra time or mobilizing additional resources.

E. Incomplete mapping coverage

20.              Production of appropriate enumeration maps for the total geographical coverage on a timely basis is almost never achieved in any country. Areas that usually are left unmapped at the time of field mapping belong to following categories:


·        Areas where access to field-mapping staff is denied by the respective owners. They may include certain commercial farms, mining areas and places belonging to private enterprise;


·        Areas not accessed due to difficult terrain conditions and lack of suitable means of transportation. These may include isolated mountainous tracts, islands and so forth;


·        Areas not accessed due to unforeseen natural calamities such as floods;


·        Areas affected by international conflicts, civil uprisings and those containing land mines;


·        Urban squatter settlements and other unauthorized built-up areas in the vicinities of major urban centres; and


·        Areas inhabited by mobile population groups.


21.              Necessary arrangements for the mapping and EA demarcation in these areas are generally made in consultation with local administrative authorities just prior to commencement of enumeration. Enumerators deployed to these areas are shown the boundaries of their assignments by the respective supervisors at the time of field canvassing. Based on enumeration records the boundaries of EAs are subsequently incorporated into corresponding base maps and digital map files for future reference and use.


22.              Cases of incomplete mapping have also occurred in several countries in respect of areas other than those mentioned above, although the degree of incompleteness has been quite variable. The main factors responsible for the incomplete mapping can be attributed to delayed start, slow pace of work, grounding of field operation due to inadequate and interrupted logistical support, inadequate supervision and quality control and lack of proper base maps, particularly in the densely populated squatter settlements.


23.              Alternative strategies—such as using the EAs of the past census by revising them through quick counting of households, splitting larger EAs at the time of field canvassing, recruiting additional enumerators for deployment to any EAs found overgrown at the time of enumeration, etc.—were adopted to circumvent the gaps in mapping. However, these measures have proved of very limited success in most of the cases. The use of old maps in the census enumeration has led to incidences of higher than normal levels of underenumeration.


24.              Incomplete mapping has generally occurred in the situations of inadequate resources, but its severity can be mitigated to a certain extent by better resource management and adoption of other appropriate remedial strategies as indicated below:


·        Timely delivery of inputs to keep the field mapping going without any interruptions. Frequent occurrences of sitting and waiting time not only adversely affect the work momentum and thereby the overall progress rate but also lower the morale of staff;


·        Soliciting cooperation and involvement of local government and traditional chiefs to secure better public support and cooperation;


·        Making necessary provisions for revising enumeration maps of unmapped areas at the time of enumeration by deploying additional cartographic staff to such areas;


·        Securing stronger government commitments to provide additional resources in a crisis situation; and


·        Prudent planning and management of resources and scouting for additional resources to cover any unforeseen gaps on a timely basis.

F. Deficient enumeration frame

25.              Deficiencies in any enumeration area frame can be described in terms of its inability to fulfill basic criteria that were set to guide delineation procedures. Following are the main criteria that have been recommended for the demarcation of EAs for the 2000 round of censuses:


·        Comparability with past censuses,

·        Capability to produce data for smaller areas,

·        Flexibility to produce data for various systems of administrative and statistical     subdivisions in the country,

·        Suitability for sample surveys and other data-collection activities,

·        Sustainability,

·        Usefulness to data dissemination and analysis,

·        Compatibility with GIS database/applications development requirements, and

·        Identifiable boundaries and compactness of shape.


26.              By and large, these criteria have been adopted in most countries but with variations caused by local conditions and requirements. In the countries where censuses were held in the past, attempts have been made to revise and improve on the existing frames. In others the methodology adopted for EA demarcation has differed from one country to another due mainly to variations in terrain conditions and administrative or socio-political structures. In some countries EAs have been demarcated along visible ground features while in others the boundaries of grass-roots-level divisions or social structures are used as the base.


27.              EAs demarcated along visible physical features often cut across the boundaries of villages and other grass-roots subdivisions. Such a frame, therefore, is not conducive to producing data for smaller areas, which now are very much in demand due to a growing emphasis on decentralized governance and microeconomic development planning. It also makes the task of identifying EA boundaries on the ground somewhat difficult, particularly when EAs are demarcated along unstable features such as tracks, footpaths or seasonal streams.


28.              In order to meet the rising demand for data for smaller areas, census offices in most countries have decided to demarcate EAs based on the framework of villages, localities or other low-level social structures. EAs delineated by this method would not cut across village or locality boundaries and therefore facilitate production and dissemination of census data for smaller areas. An added advantage of this approach is the involvement of local chiefs in the process of EA demarcation and census enumeration which obviously, among other advantages, helps in identifying isolated households in remote rural areas which otherwise are liable to be missed in the count.


29.              Retention of EA boundaries is another prime requirement to achieve comparability of data between censuses and create a stable GIS database. Since the size of the population in most developing countries is increasing, the number of EAs delineated for one census is liable to increase by the time of the next if the EA size remains constant. This would entail splitting of overgrown EAs. However, the number of such EAs can be kept to a minimum if they are demarcated based on the lower thresholds of the prescribed range of population size.


30.              Despite adherence to the above criteria and considerations for their demarcation, EA frames produced for the 2000 census round have been found to contain several deficiencies which, in turn, lead to difficulties encountered by field enumeration staff in using the EA maps at the time of enumeration. The most common deficiencies found in the EA maps are as follows:


·        Ambiguities in identifying EA boundaries drawn along unstable features like tracks or footpaths, which are liable to change over time due to climatic factors and population movements;


·        Oversized EAs created mainly because of use of household or structure counts to determine the size of EAs;


·        Household counts obtained from local chiefs based on the extended family system;


·        EAs delineated to cover only built-up areas, leaving vast parcels of land used for farming or pastures or left for future development unaccounted for by any EAs;


·        EAs spreading over large geographical areas that cannot be covered on foot at the time of enumeration, particularly in sparsely populated areas;


·        EAs not being compact in shape leading to confusion at the time of enumeration. These include the EAs of donut shape or I-shaped, those comprising isolated pockets, lump EAs, and so on;


·        Stacked EAs demarcated in high-rise and coextensive buildings often pose problems in correctly identifying them on the ground;


·        Composite EAs assigned to two or more enumerators at the time of enumeration. Splitting of such EAs on maps at a later stage poses serious problems;


·        EA boundaries demarcated along imaginary lines but not made adequately identifiable by plotting adjoining benchmark features or locations; and


·        Variations in the spellings of place names used on the maps, which differ from those known by the local populace.


31.              Strategies and procedures adopted in certain countries that lead to minimization of deficiencies in their enumeration frames include:


·        Determining EA boundaries in the field so that they are made adequately identifiable by plotting additional reference features, wherever necessary;


·        Subjecting base maps used for EA delineation and map production to thorough updating and comprehensive content enhancement by incorporating adequate geographical features and related attribute details using GPS;


·        Determining the size of EAs based on population counts and not the number of structures or households, as practised in some of the countries;


·        Involvement of local government bodies and traditional chiefs to help in identifying realistic boundaries of lower subdivisions which, in turn, would provide a more realistic and sustainable framework for demarcation of EAs;


·        Splitting of any larger EAs along identifiable boundaries at the time of enumeration and drawing the boundaries on the provided maps before assigning EAs to two or more enumerators;


·        Establishing realistic and commonly used place names with the help of local administration and other concerned departments; and


·        Harmonization of the census frame with other systems of social and political subdivisions by involving concerned government departments in the process.

G. Deficiencies in the national master sampling frame

32.              Area frames used for the sample design and planning and conduct of sample surveys are usually drawn from the enumeration frames created for the preceding census. Deficiencies or shortcomings contained in the census frames will, therefore, vitiate the sample frame if they are not properly rectified beforehand. As operational requirements of the census and surveys are not exactly the same, it is imperative that census EAs are appropriately enhanced and modified to make them suitable for survey requirements. Creation and usage of a deficient sampling frame would lead to production of biased population estimates.


33.              Sampling frames being used in certain countries have not been properly designed and enhanced to meet the requirements of survey enumeration. For a proper sample design it is necessary to have good sampling frames, but to obtain reliable population estimates these sampling frames must also be correct as of the census night. This calls for a thorough updating and reconciliation of census enumeration frames by incorporating all changes that might have occurred during the period between cartographic fieldwork and the enumeration reference date. Other corrections and revisions marked by census enumeration staff on the maps provided to them must be incorporated as well. In general, these corrections and revisions may include the following:


·        Splitting of larger EAs created due to use of population estimates derived from household or structure counts;


·        Subdividing territorially larger EAs;


·        Incorporating EAs delineated in the localities not discovered or visited at the time of field mapping;


·        Making changes in the size and boundaries of EAs caused by unforeseen population movements;


·        Incorporating EAs that are created at the time of enumeration. These may include EAs delineated in new built-up areas that did not exist at the time of field mapping; areas inhabited by mobile population groups which usually are not delineated during field mapping; isolated areas not accessed at the time of field mapping; EAs returned for special category areas such as hospitals, army barracks, hotels and so forth; EAs covering non-static and volatile population groups such as internally displaced persons, international refugees and so forth;


·        Recasting and adjusting EA boundaries demarcated on the sketch maps;


·        Extending EA boundaries to include adjoining uninhabited areas left unaccounted for;


·        Making precise boundary adjustments of rural EAs with the adjoining urban EAs demarcated on large-scale layout maps, if any variations are noticed;


·        Aligning EA boundaries precisely with the boundary-forming features; and


·        Incorporating other corrections marked by enumerators. They may include spellings of place or feature names, new features or places, boundaries and others. 


34.              Adoption of proper procedures is also important to create an efficient sampling frame. The procedures should be determined by taking into account the size variations in census EAs and the specifications of sample design. An outline of the procedures successfully used in several countries for creating a sample frame for intercensal surveys conducted after their 2000 round censuses is provided below:


·        Determining the relevant strata according to type of areas and population characteristics, such as rural and urban, mining and commercial areas or mobile population areas, and demarcating these on the corresponding census base maps;


·        Listing of Primary Sampling Units (PSUs) for each stratum. A PSU may comprise an EA or combination of several EAs. Since census EAs have considerable size variations, it would be advisable to create PSUs by grouping census EAs into more homogenous and equitable units. Thus each PSU may contain about 2,000 persons and accordingly about four EAs;


·        Selection of the sample at the PSU level for creation of the master sample frame. The national master sample frame may cover about 20 to 25 per cent of the total PSUs in the country;


·        Updating and content enhancement of EAs contained within the PSUs included in the national master sample frame. The EAs need to be made more elaborate, authentic and unambiguously identifiable on the ground as they are to be used by different enumerators at different points in time; and


·        During updating, EAs should, preferably, be subdivided into identifiable segments or blocks, as this would facilitate listing of households (ultimate sampling units) at the time of the actual survey.


35.              Updating and enhancement of EAs contained in the national master sample frame have been constrained in most countries due to lack of adequate resources. Budget allocations made for the conduct of sample surveys usually are not enough to accommodate launching of separate map updating and upgrading operations. However, strategies of map updating adopted in certain countries have proved quite cost-effective and successful. They are summarized below:


·        To save on resources and time, the updating of EA maps should be carried out concurrently with the survey enumeration. For this purpose joint survey teams, each comprised of survey enumerators and one or two cartographers, should be created;


·        On the first day of enumeration, the joint team should verify the limits of the selected EA with the assistance of local administration or traditional chiefs. Thereafter, while survey enumerators begin household listing the cartography staff should update and enhance the EA map using the vehicle provided to the team. A sketch map prepared by cartographers should be used to verify the list of households before making the selection of sample households;


·        On the following day, while the survey team is administering the survey questionnaire, the cartography staff should quickly verify other EAs included in the PSU. Comprehensive updating and upgrading of these EAs would be done when they are selected for any surveys; and


·        Households selected for the given survey should be located on the EA map if the survey is planned to have more than one round.

H. Automated mapping and GIS applications

36.              Automated mapping was adopted by the statistical offices in most countries during the previous census rounds, but its applications were limited to production of publication maps. Only in a few technologically advanced countries were enumeration maps produced using computerized mapping systems. However, due to rapid advancements in digital mapping and GIS during the last decade, many countries have, for the current census round, embarked on the development of comprehensive GIS database and applications to produce maps needed for the planning and conduct of enumeration as well as other post-enumeration activities. In some other countries where censuses have already been held, plans are under way to initiate GIS database development using maps produced during the pre-enumeration phase for future use.


37.              Development of GIS database and applications to produce enumeration maps for countrywide coverage in some developing countries has been made possible because of involvement of other national stakeholders, provision of substantial technical and financial assistance by donor countries and the ability of the census offices to mobilize adequate resources to outsource the major tasks to private enterprise. In countries where similar supports could not be organized, the development of a digital map database has been completed for only a part of the country. But these countries have plans to continue the process of GIS database development and complete remaining areas before the next census.


38.              The main problems encountered during the process of developing GIS database and applications to produce enumeration maps and lessons learned in certain countries where GIS projects have been implemented for the first time, are as follows:


·        Lack of proper and up-to-date base maps and materials, particularly for the rural areas which account for a major part of the area and population of the country;


·        High costs involved in acquiring more timely data from alternative sources, such as high-resolution satellite imagery, low-altitude aerial photography and so forth;


·        Non-compatibility of digital data obtainable from other national GIS users due mainly to variations in the data source, accuracy and precision standards adopted for data capture and software used;


·        Lack of trained staff in the national statistical offices for deployment to GIS activities and implementing quality control checks on the data and map files delivered by private contractors;


·        Lack of resources to maintain and update the database created with the involvement of private enterprise and the GIS infrastructure set up with the assistance of external support.;


·        Maintaining control of data sharing and its confidentiality, particularly when data capture and digitizing are performed by private companies in their own establishments located outside the country; and


·        Outsourcing of highly technical tasks to a private GIS company prohibits development of in-house capacities, which in turn may lead to perpetual dependence on outside sources and may prove to be more expensive in the long run.


39.              The following recommendations and observations may be useful, particularly for developing countries that are planning to use GIS technology for the production of census enumeration maps:


·        As the development of a GIS database is expensive and time-consuming, it should commence with sufficient lead time to ensure its timely completion for production of enumeration maps;


·        The GIS project in the statistical office should be planned and implemented as a joint venture with involvement of other national stakeholders and potential GIS data users. For such a venture it is important that issues concerning costs and data sharing are explicitly defined in the initial stages;


·        Where resources are scarce, GIS database development should be planned as a long-term activity and implemented in a progressive manner. The data for towns and other densely populated areas that account for the major share of the national population should be captured first and processed to produce enumeration maps using automated procedures. For other areas, maps can be produced by conventional manual procedures;


·        Alternatively, data pertaining to boundaries (administrative and data collection frame) may be captured in a vector format and overlaid on the scanned images of relevant maps or materials (topographic maps, urban layout maps, aerial photos, satellite imagery, etc.) for the production of EA maps; and


·        Selection of GIS equipment (hardware and software) should be made considering the system used by other government departments. Such an arrangement would promote the exchange of data, sharing of experiences and organization of joint training.

I. Outsourcing of GIS and mapping activities

40.              Outsourcing of census mapping and GIS activities has not yet become a common practice, especially in developing countries. In most countries, competent private GIS companies capable of providing services at a scale necessary to perform census mapping have not yet emerged. Secondly, the resources mobilized through the national as well as donor funding for the census mapping project are often not adequate to support outsourcing of the mapping exercise to private enterprise.


41.              However, statistical offices in certain countries that planned to create a comprehensive GIS database from scratch for the first time within a limited period found it inevitable to involve private enterprise in implementing their census GIS project. The implementation approach adopted in these countries represented a work-sharing arrangement whereby the base map updating and field data collection are generally accomplished in-house by the statistical offices themselves, while tasks of a highly technical nature, such as setting up the GIS system, data capture and integration and creation and production of enumeration maps, are awarded to private companies.


42.              The process of implementing a GIS project jointly with private contractors has not been very smooth as conceived initially. The main problems encountered and certain other related issues are indicated below:


·        Because of the high costs charged by private companies, the resources allocated for the entire mapping project are often consumed during the pre-enumeration phase itself. As such, continuation of mapping activities to process and produce maps needed during the post-enumeration phase is adversely affected;


·        Most of the GIS companies do not have the necessary experience in census mapping. The initial proposals formulated by them are, therefore, subject to frequent revisions resulting in new elements that not only substantially add to the initial costs but also hamper the rate of progress. This increases the risk that maps will not be produced on time;


·        Some companies do not have the requisite capacity and infrastructure to carry out relevant tasks themselves. They generally subcontract these tasks to other professional individuals or contractors. This not only causes delays in the delivery of outputs but also increases the costs;


·        In the absence of in-house GIS capabilities, it becomes difficult for the census office to make qualitative checks on the data created and delivered by the contracted companies. This often results in delivery of inaccurate and deficient data, which in turn affect the quality of the maps; and


·        Awarding implementation of highly technical activities to private companies precludes development of relevant capacities within the census office, which is crucial for the management and maintenance of the database and the production of maps needed for other operations undertaken during the post-enumeration phase.


43.              Countries planning to outsource their census GIS mapping activities to private contractors may take the following precautions into consideration to ensure successful implementation:


·        The track record of the company being contracted must be thoroughly checked and verified from the clients who have received services from them in the past;


·        The contract should clearly indicate precise specification of the final outputs to be delivered and not the activities involved. Experience shows that these companies often inflate the activity list to justify higher costs charged by them;


·        The timetable of the delivery of outputs should be explicitly indicated in the memorandum of understanding with inclusion of a clause indicating pecuniary penalties (amount to be charged per day or week) if the contracted company fails to deliver specified outputs or services within the stipulated time;


·        If the contract also includes setting up a GIS system, it should be ensured that the system provided is compatible with those used by other users in the country. The agreement should provide for training national staff on basic functionality of the equipment (hardware and software); and


·        The issues relating to copyright and ownership of data must be clearly indicated in the contract. Generally private companies sell the data acquired and paid for by the census to other users to maximize their profits.

J. Post-enumeration mapping programme

44.              A post-enumeration mapping programme generally covers the mapping activities that are carried out after the census enumeration. Some of these activities are related to the pre-enumeration phase, while others are initiated afresh to support the activities undertaken during the post-enumeration and intercensal phases. The main mapping activities carried out during the post-enumeration phase are as follows:


·        Retrieval and archiving of pre-enumeration resource maps and materials;


·        Updating, enhancing and reconciling census enumeration and data-reporting frames;


·        Development and maintenance of GIS database and applications;


·        Processing and production of census publication maps and other general reference maps;


·        Creating, updating and maintaining sampling frames; and


·        Provision of cartographic inputs and services to other user-specific applications.


45.              Thus, implementation of the post-enumeration phase of census mapping is crucial not only to promote proper utilization of census data in planning and research activities but also to keep the census base maps up to date for future uses. For the countries where enumeration maps have been produced using automated processes, it is essential to keep the cartographic activities ongoing to maintain and improve the GIS database and share it with other users to expand its utilization.


46.              However, the post-enumeration phase of mapping, so far, has not been given due importance in the planning of census cartographic programmes and resource allocation. Consequently, area reference maps showing boundaries of various subdivisions, for which population data are produced, have been prepared and incorporated into the contents of relevant data publications in only a few countries. It hardly needs to be emphasized that these maps assume a significant role in understanding and analysing census data in a more meaningful way.


47.              Similarly, production of thematic maps can effectively help in sensitizing and educating the potential data users and the public at large on spatial dimensions and inter-relationships of population variables and thereby motivate them to integrate population indicators in planning, monitoring and evaluation of programmes and research relating to socio-economic development. Production of these maps has not been undertaken at an adequate scale in a majority of the countries.


48.              Only a few countries, where the censuses for the 2000 round have already been held, have embarked on the production of thematic maps for census data-analysis reports. Some of them have embarked on yet another ambitious project to produce census atlas volumes as a part of the census publication programme. In some cases, the printing of these atlases has been delayed because of a lack of necessary resources.


49.              Production of other publications predominantly featuring relevant maps like gazetteers of place names, trends of urbanization, geographical studies of migration and other population phenomena have been attempted in some countries. These and other similar publications can be easily produced in countries where GIS database and applications have been developed during the pre-enumeration phase.


50.              Following are some basic considerations which, if given due attention at the planning stage, can contribute to the successful implementation of post-enumeration mapping activities:


·        Preparation and production of publication maps should be included as an integral component of the overall census cartographic programme at the initial stages of planning and resource allocation; and


·        Production of thematic maps in the form of census atlases should be undertaken as a national task by involving other stakeholders, such as ministries of education and health, local governments, research and educational institutions and other data users.

*       This document was reproduced without formal editing.

**     UNFPA, Zimbabwe.  The views expressed in the paper are those of the author and do not imply the expression of any opinion on the part of the United Nations Secretariat.