Addressing the challenges associated with census mapping in Africa Hennie by guy21


									     Addressing the challenges associated with
            census mapping in Africa

                                         Hennie LOOTS
                           Director, GeoSpace International, South Africa

       Abstract. The role of maps in a census is to provide the cartographic basis for enumeration
       and the platform for spatial census data products such as census atlases. This paper focuses
       mainly on mapping solutions for enumeration. The paper assesses the traditional methods of
       census mapping in African countries and aims to provide modern alternatives to the traditional
       methods that are realistic and achievable given the unique circumstances of the African
       continent. The paper is therefore of a practical rather than an academic nature. The author
       strives to provide hands-on and practical solutions based on experience gained in several
       countries over the last decade. The paper could therefore be of potential use to readers that are
       responsible for the planning and implementation of the 2010 round of population and housing

1.     Introduction and problem statement
The aim of a population and housing census is to collect, process and publish data on every
individual within a defined geographical area usually a country. The aim of census mapping is
to provide the cartographic basis to be used during the actual process of counting. The census
cartographer therefore needs to provide the census enumeration team with a set of unique maps
covering the entire country that accurately defines the boundaries within which each
interviewer (enumerator) has to work during the enumeration phase of the census.

In order to do this the census cartographer needs to have access to current maps of sufficient
levels of scale and detail. In most African countries the required maps are either very old (often
30 years and older) or in some cases do not exist at all.

Furthermore the census cartographer usually relies on a very small permanent staff and a huge
temporary workforce, funded directly from the census budget, to execute the census mapping
plan. This is due to the fact that most statistical agencies in Africa are understaffed in general
and seriously understaffed in terms of cartographers. It can therefore be stated that the capacity
within statistical agencies in Africa to do census mapping is in most cases limited.

2.     Conventional mapping
With the above being the status quo in most statistical agencies in Africa the mapping solutions
in the past tended to focus on arriving at solutions within the existing framework rather than
transforming the existing framework as part of the solution. Given the circumstances and the
constraints that faced census cartographers most countries over the years adopted an approach
of throwing extensive human resources at the problem once funding for the census become
available. This approach implied that huge numbers of people (often referred to as field
mappers) were deployed in the field to sketch enumeration area maps whilst sweeping the
larger administrative area. The rationale behind this approach was to solve the lack of proper
base maps by updating the maps in the field or by creating entirely new maps in the field.
During the 2000 round of censuses this methodology was refined with the introduction of
Global Positioning System (GPS) technology. GPS contributed to the increase of the absolute
accuracy of map updates and sketch maps. The conventional approach provided and today still
provides a workable solution in most African countries.

3.     Why the need for change?
It can perhaps be argued that it is not necessary to revisit the conventional methods since it
provided workable solutions in the past. There are however many reasons why there is a need
for change:

3.1      User needs
The information age that we are current living in places more and more demand on the need for
digital spatial data. This is also the case in Africa. Furthermore the need for quality and relevant
statistics for developmental planning purposes is bigger than ever. A statistical agency therefore
has to adjust in order to the respond to the spatial data needs of their users. Some statistical
agencies are currently responding to user needs by using Geographical Information Systems
(GIS) in post-enumeration activities (only). Although this is a step in the right direction it is
argued that more emphasis should be placed on the use of GIS and geographical information
technology (GIT) in pre-census activities. In doing so the platform for small-area (spatial)
census data products are created as a direct deliverable of the methodology.

3.2      Advances in technology
GIT has advanced by leaps and bounds over the last few years. The processing power of
computers and software packages are increasing by the day. Moreover, the integration and
utilisation of GIS, GPS and remote sensing are also becoming easier and more cost effective.
There can be no doubt that the right tools exist and it has never been easier to utilise these tools
in geospatial applications. It is argued that, if implemented as part of a population and housing
census project, the technology is now within the financial reach and technical capabilities of
most statistical agencies in Africa.

3.3      The cost factor
Although the initial financial layout required for the establishment of a GIS Office at a
statistical agency is still relatively high it is a much more affordable exercise than say ten years
ago. Furthermore, if applied optimally, a statistical agency can recover the initial capital layout
of the GIS infrastructure from the savings in the mapping sub-project of the first population and
housing census that will benefit from the technology. This is made possible mainly by
significant savings brought about by streamlining the pre-enumeration census demarcation
fieldwork exercise.

3.4    Capacity building
The future of census mapping is digital. All developed countries are already using it. The
sooner all statistical agencies starts building the required capacity the better since international
standards and the overall demands driven by the information age will eventually demand
statistical agencies to do so. It must be mentioned that building the required capacity is
nowadays much more realistic than before since the technology (GIS, GPS, satellite imagery,
digital aerial photography, etc.) is a lot easier to use and integrate than before.

3.5     The issue of quality
If digital census mapping is applied correctly and optimally it is guaranteed to provide better
quality results when compared to conventional mapping. The normal errors associated with
census mapping such as incomplete coverage or double coverage of the same area is to a large
extent eradicated.

3.6    International trends:
The United Nations (UN) [1] are promoting the use of GPS, Digital Imagery and GIS with
Census Mapping. It can therefore be expected that more countries will be encouraged and
empower by the UN to implement digital census cartographic methodologies in the 2010 round
of censuses.

4.     Modern (GIT) methods
Modern methods assume the optimal utilisation and integration of GIT tools. GIT tools include:
GIS (including desktop GIS, mobile GIS and WEB GIS); GPS; remote sensing (satellite
imagery and digital aerial photography).

It is important to understand the technical capabilities of current GIT tools, but it is also
important to keep in mind that the crux of the matter is really the optimal integration of the
available tools in order to arrive at the best possible solution for a given country. Experience
has shown that no two countries have/will have the same solution. This is due to the fact that
countries are unique in terms of the combination of variables that dictates the optimal solution
that can be realistically implemented. These variables include population size, population
distribution, settlement patterns and densities, geographical area, availability and specifications
of base maps, agency capacity with regards to GIT, the census mapping budget, timeframe for
implementation and commitment to the transition from conventional to modern census mapping
methods at senior management level. If these factors are not taken into consideration and the
available tools are not optimally used and integrated as part of a total census mapping solution
it could easily become more of a hassle to the census cartographer than an aid.

4.1     Technical capabilities of GIT tools
GIT tools have developed tremendously over the last decade whilst at the same time becoming
more and more affordable. GIS software and hardware is much more powerful, flexible and
easier to use than was the case a few years ago. GPS receivers are more user-friendly and
communicate elegantly with most GIS platforms. Mobile GIS with integrated GPS provides so-
called “moving maps” that enable fieldworkers to navigate with relative ease to an area to
collect spatial and attribute data. Electronic forms eliminate the need for paperwork. WEB-GIS
is becoming more and more popular for census and survey operational management as well as
dissemination of all statistical data with a geographic link.

Remote sensing in census and survey mapping is not Remote sensing (satellite imagery and
digital aerial photography (DAP)) nowadays enables the census cartographer to have access to a
GIS-ready base map for an entire country that meet all the needs of the census (i.e. currency,
accuracy and level of detail). This technology enables the census cartographer to have a detailed
base map for the entire country that is less than two years old thus eliminating the problems
associated with dated base maps. This base map is suitable to be used as the base map for
enumeration area and supervisor area maps. Because of differences in population characteristics
(mainly geographic spread and densities) in urban and non-urban areas there are different base
map solutions for urban and rural areas.

4.2     Rural base map: the SPOT5 solution
SPOT5 is the first commercial satellite that provides a feasible base map solution in terms of
specifications and cost for census mapping purposes at a national (total coverage) level. The
latest SPOT5 2,5m (pixel resolution) natural colour satellite imagery in particular provides the
ideal base map for rural and even less dense urban areas. The technical specification of the
imagery, as well as the ability of the satellite to do image acquisition of vast geographical areas
such as national coverage’s linked to fast image processing capabilities ensuring relatively short
delivery schedules, makes it an attractive option for census mapping purposes. Although still
costly it is within the census mapping budget of most countries – especially if one takes into
account the huge savings that can be made in reduced EA demarcation fieldwork as a result of
the inherent benefits of having a detailed base map. SPOT5 5m natural colour imagery is lower
resolution product from the same satellite. It is significantly cheaper than SPOT5 2,5m but there
is an obvious compromise in terms of pixel resolution. A major advantage of SPOT5 5m is that
the archive coverage on this product is, for most parts of the world, much more extensive than
is the case with the SPOT5 2,5m archive. The archive imagery is cheaper than the programmed
imagery and it takes the risk out of programmed image acquisition. Programmed image
acquisition is determined by prevailing weather conditions as well as the priority of a given
image acquisition project in relation to other projects at a given point in time. This is due to the
limitations on the onboard storage capabilities of the satellite. SPOT Image is however
currently the only satellite company that provides the client with a feasibility study prior to
ordering the imagery. The feasibility study tells the client how realistic it is to acquire the
required imagery within the timeframe of the project. It takes into account previous experience
based on the extensive historical image acquisition database of SPOT image as well as other
important factors such as prevailing weather patterns and the effect of seasons on image
acquisition 1 .

With a detailed base map sketch mapping becomes unnecessary as well as extensive GPS
fieldwork. SPOT5 2,5m natural colour supermode imagery is currently being used, for the first
time ever in a population and housing census project, in the census mapping project of the 2006
Population and Housing Census of Lesotho. The project is currently still in progress but
indications are that it will be a huge success. Ethiopia has also made provision for the
acquisition of the same imagery for their 2007 census. This imagery is perfectly suited for rural
areas as well as less dense formal urban settlements. The SPOT5 5m archive is furthermore
quite extensive enabling statistical agencies to have access to relatively current imagery (<2
years) within a relatively short period of time.

4.3    Urban base map: Very high resolution satellite imagery and Digital Aerial Photography
Research has shown that colour imagery with a pixel resolution of about 0,5m or better is
required for urban areas in general but specifically for high density informal urban settlements.
High-quality examples of the 0,6m Quickbird satellite imagery 2 or, in certain cases even 1,0m

    See for more information on SPOT imagery.
    See for more information on Quickbird imagery.
IKONOS imagery, can be considered for relatively large contiguous informal areas. In cases
where there are however several small high-density settlements scattered all over a country (as
is often the case) the fastest and most cost effective solution is the creation 0,5m colour digital
aerial photography 3 . In this scenario satellite imagery usually also becomes relatively expensive
(effective price per square km or hectare) because the user has to acquire minimum coverage
imagery based on a pre-defined grid or footprint that is often much bigger than the area of
interest or the area of interest might fall into two or more image blocks necessitating the
acquisition of more than one image hence pushing the costs up even further.

A huge advantage of satellite imagery in general compared to aerial photography is that it does
provide a workable solution in countries where it is difficult to obtain the required flight
authorisations to do aerial photography (in a short period of time). Most satellite operators
furthermore collect imagery on a continuous basis irrespective if the satellite is programmed for
a specific customer or not. This implies that huge archives of data are constantly being
collected. The archived data are usually cheaper than programmed data and will often suffice
for census purposes – especially the data collected within two years before census day. For
most satellites the archived data over Africa is however relatively limited compared to certain
other parts of the world because the decision on where to collect archive imagery is mainly
driven by potential future sales (of the archived imagery).

One of the biggest disadvantages of satellite imagery is that the image quality can vary
significantly. This is ascribed to the variances in atmospheric properties that are caused and
influenced by several factors including the effect of seasons, the effect of water masses and
proximity to the equator. This is an important consideration given the fact that both the urban
and rural satellite imagery solutions mentioned above pushes the technical capabilities of the
respective satellites to their limits hence allowing virtually no room for inconsistencies in image
quality. This is due to the fact that the satellite imagery available today is in essence only just
suitable for census base map purposes. As image properties and resolution improves with newer
satellites over the next few years this problem will however seize to exist.

DAP has proved to be the best solution for the creation of census base maps in high density
urban settlements. DAP can be created at different pixel resolution usually starting at about
1,5m going down to as little as a few centimeters. This is important since the best pixel
resolution for a given application can be determined on a case-by-case basis ensuring that the
imagery will provide the required output. The biggest advantage of DAP is however the
flexibility in the creation of the imagery. If say 100 urban areas within a country has been
earmarked for digital aerial photography, it can be scheduled in such a way to optimise the
weather conditions as well as the needs of the census mapping office. Experience has shown
that it is by far the quickest and cost-effective method to create base maps for scattered small

Indicative of the quick turn-around time of digital photography creation is a sample survey
mapping project that GeoSpace International [4] did in 2002 in South Africa. For this project
digital aerial photography base maps were created for 970 areas scattered all over South Africa.
This was done with one dedicated aircraft in less than three months. The significance of this is
that census cartographers can now have access to a detailed image map of high density and
often dynamic urban populations as close as possible to census day.

    See for more information on digital aerial photography.
4.4     GPS
During the 2000 round of censuses GPS played an important role mainly to provide positional
(absolute) accuracy to sketch maps. It was the first GIT tool that was used widely and with
reasonable success in Africa. It was however used in isolation of other GIT tools mainly
because other GIT tools were in most cases not used at all. For the 2010 round of censuses the
role of GPS is likely to differ significantly from its role in the past. Since GIS implicitly creates
coordinates as spatial data (vector or point) is captured it is no longer necessary to use GPS
primarily to capture coordinates. A map (image or otherwise) created from a GIS provides the
basis for the capturing of point and vector data in the field hence making it unnecessary to use
GPS for this purpose. GPS is therefore used for navigational purposes to ensure that the right
area on the ground is visited and as a quality control tool to ensure that the team was actually in
the areas where they were supposed to have been. GPS is furthermore integrated into GIS
making it completely unnecessary to transcribe any coordinates and thus eliminating one of the
biggest sources of errors in the use of GPS. Data is simply downloaded from a computer into
the GPS receiver or uploaded from the GPS receiver into the computer. GPS can furthermore be
directly linked to mobile GIS enabling the use of so-called moving maps. This approach
completely eliminates the need for any map annotations and the use of paper forms during
mapping fieldwork since all data capturing is done directly onto a field computer linked to a
GPS. Some of the latest model GPS receivers have built-in moving map functionality thus it
further streamlines fieldwork by eliminating the use of a field computer.4 .

4.5     GIS
GIS is arguably the most important of all the GIT tools. GIS is the tool that is used to integrate
all the other tools. It is used for the accessing and manipulation of all existing spatial data
relevant to the census project. It is used for the accessing and processing of newly acquired
image base maps. It is used for the integration of all the different spatial and attribute data
sources and for the creation of fieldwork maps in electronic or hardcopy format depending on
the fieldwork methodology. It can even be used to do preliminary EA demarcation in the office
prior to fieldwork in order to limit the time in the field even further. It is therefore of critical
importance during the preparations for EA demarcation fieldwork. All fieldwork maps in are
created using GIS. After the fieldwork the updating of the spatial and attribute data base is done
using the GIS. The creation and printing of all the final EA and SA maps are also done using
bulk map creation and printing tools that are developed on a GIS platform.

From the above it is clear that the tools exist to make the life of a census cartographer a lot
easier. The challenge is the successful integration of the different tools in a total mapping
solution. The author is therefore strongly of the opinion that the total solution is far more
important than the using of the different tools in isolation. The real power of GIT is maximised
when the different tools are properly integrated! This implies a complete rethinking of the
census enumeration area demarcation methodology. Following is the process flow of a typical
GIT-driven census mapping project:

    See for more information.
                    Project initiation
  Training                                               Enumeration area /
                                                          Supervisor area
                                                           data capturing

        GIS              Image           Existing
   Infrastructure      acquisition       GIS data
                                                         Enumeration area             Training
                                                        Data Base signed off

                    Data Base design
                           &                             Enumeration area /
                    implementation                        Supervisor area
 Training                                                  map creation
                                                            and printing

               Preparatory office work
                                                        Census data products
Figure 1: Process flow of generic GIT-based census mapping project

The flow specified above is made possible by the use of all three GIT technologies and the
integration of the data and tools provided by said technologies into one single system which
links to one single data warehouse. Thus, linking a specific process flow to the various GIT
options will typically look like this:

Process Flow                                            Technology Used

Creation of spatial data warehouse                      Database and GIS technology

Preparatory office demarcation                          GIS and Remote Sensing

Fieldwork verification                                  GIS, GPS, Remote Sensing

Office demarcation updating and correction              GIS, GPS, Remote Sensing

Enumerator map creation and printing                    GIS and database technology

Enumeration tracking and monitoring                     GIS

Spatially enabled web application design and GIS, Web GIS, statistical andlysis and
implementation                               database technology

Table 1: GIT tools relevant for different phases of census mapping project

GIS is therefore a multi-disciplinary field integrating various other specialist fields into one
single sustainable solution. The biggest mistake one can make is regarding the above mentioned
fields as autonomous where census cartography is concerned.

5.     The GeoSpace approach
GeoSpace International is a commercial company that has been involved in demographic
projects of a spatial nature including five census mapping projects. The company was involved
in the census mapping projects of South Africa (1996 and 2001), Namibia (2001), Tanzania
(2002) and currently Lesotho (2006). Furthermore the company has been involved in technical
consultancies on census mapping and GIS in Ethiopia, Swaziland and Botswana. As a result of
the staff profile of the company we have census mapping expertise second to none on the
African continent.

GeoSpace’s approach for the implementation of digital mapping for a population and housing
census project consist of the following basic steps:

5.1     Needs assessment and user specification
During this step a thorough assessment is done of the status quo regarding GIS and the census
preparations in general. The exact expectations with regards to the census mapping project are
also identified and documented.

5.2     Project proposal
Based on the needs assessment and user specification and taking into account the status quo
regarding GIT, a detailed project proposal is prepared in consultation with the relevant
counterparts from the national statistical office (NSO). This project proposal documents the
details of the most realistic census mapping solution for the particular country. The proposal
would typically take into account the spatial data available for the country; the current census
mapping methodology as well as the census mapping budget.

5.3    Project Implementation
Once the project proposal has been adopted by the census management/NSO the project is
implemented. Since modern census mapping methods are relatively new to most census
cartographers in Africa it is important and necessary for the CSO to have access to the required
subject matter and GIS technical expertise. During project implementation GeoSpace usually
provides the CSO with support with regards to training; base map data acquisition, project
management and technical issues.

5.4    Capacity building
A key strategic focus of GeoSpace is to part with knowledge. This is important to the company
not only because capacity building is important and necessary for the NSO but also because the
more GIS users there are the more GIS industry as a whole will be stimulated. Moreover, the
only way to really understand GIT is to do the work oneself. Geospace’s approach is therefore
focused on training the local staff to do the work and then providing management support
during the census cartography process itself, where possible.

5.5    Technical assistance
Since the technology as well as the modern methodology is usually new to the NSO it is
important to provide technical support throughout the project to ensure the success of the
project. GeoSpace provides the required GIS and subject matter technical support.
5.6    Project management
GeoSpace has a proud record of project delivery. The Company has, up to date, not been
involved with a census or survey mapping project that was not a success. One of the main
reasons for this has been the fact that GeoSpace only exits from the project once the final
deliverables have been met. Since GIT is a new concept GeoSpace normally prefers to be
involved in the day-to-day project management of the mapping project. This enables the
Company to identify possible problem areas early and to take remedial action before the
problem gets out of hand to ensure that the project delivered as was outlined at the beginning.

6.     The Challenges
Although the benefits of modern methods in census mapping are obvious there are several
challenges associated with the migration from paper to digital mapping. Some of the more
significant challenges are as follows:

6.1     Ignorance at the technical level
Statisticians and cartographers at the technical/operational level often feel threatened by the
idea of introducing GIT into their organisations or projects because they either do not know
what it can do or do not want to go through the perceived hassles of learning what it can do and
how to do it. As a result it is often more convenient to remain ignorant. Other contributing
factors are the fear of change and the fear amongst (certain) staff that they might become
redundant once the technology is implemented.

6.2    Ignorance at the decision making level
Often decision makers within a NSO are not aware of the merits and implications associated
with the modern approach to census mapping. There is also the perception that GIT is
expensive and would bring unnecessary complexity to the (census mapping) project. The
expertise required to provide decision makers with the right information to shape policy and
decision making is often not available within the organisation and also not easily accessible
from elsewhere and hence (negative/wrong) perceptions tend to drive decision making process.

6.3     Paradigm shift
The implications of the migration from paper to digital are severe and hence it requires a
paradigm shift within the cartographic unit of an NSO as well as the organisation as a whole. It
cannot be implemented partially or half heartedly – failure is almost guaranteed if commitment
and buy-in from the highest level within the NSO is absent. It is therefore important that the
organisation needs to undergo a paradigm shift with regards to their thinking of spatial data and
the role it plays in the collection, analysis and dissemination of statistics.

6.4    Fear for the risk of failure
A failed census mapping project will almost certainly guarantee a failed census or lead to a
postponement of the census – both of which have serious negative implications for the NSO. As
a result statistical agencies often prefer to follow the tried and tested conventional approach
because they are familiar with the methodology and have better control over the delivery
thereof. What makes matters even worse is that there are a number of examples where GIS/GIT
implementation has ended in disaster.

6.5     Capacity
Most statistical agencies in Africa do not have the required capacity (human, financial,
infrastructure, etc.) within the organisation to successfully implement a GIS. This is a serious
constraint since GIS implies hardware, software, data and human resources and not only a sub-
set thereof. It should however be noted that there are also often misconceptions about the
financial implications of GIS. It is sometimes argued that GIS cannot or should not be
implemented because it is prohibitively expensive. Case studies (Tanzania 2002 and Lesotho
2006) have however showed that, if applied correctly, GIT-based solutions can cut enumeration
area demarcation fieldwork by up to 80% with the resultant saving often paying for the
investment in GIS or a significant portion thereof. It is however unfortunately so that, after
completion of a census project, newly established GIS offices often die a slow (or sudden)
death because of a lack of resources to keep the momentum going. In many countries there is no
provision for GIS staff in the formal structure of the organisation because it is a relatively new
discipline. Furthermore trained GIS staff is in high demand. This leads to a situation where,
once qualified or skilled, staff often leaves the statistical agencies for greener pastures.

6.6    The need for an expert group
According to the UN [1] there is a huge need for the establishment of an international expert
group on GIT for census mapping. This is necessary to provide a forum to share experiences
and discuss and brainstorm ideas. An expert group would, amongst other things, contribute to a
more uniform approach on fundamental issues such as the role of (modern) base maps and the
optimal use of GPS in census mapping. A more uniform approach would instill confidence
amongst technical staff and decision makers within national statistical agencies. This is
necessary to ensure more informed decision making and optimal utilisation of the technology.

7.      In conclusion

The 2000 round of censuses saw the successful introduction of modern methods for census
mapping in a few African countries. It is anticipated that the 2010 round of censuses will be the
round where the revolution in census mapping will gain real momentum. Statistical agencies
therefore have an important decision to take: they can either take the step now and become part
of the international trend or they will probably have to wait another ten years for the next
opportunity to catch up with the rest of the world.

8.      References
[1] United Nations (2004), Integration of GPS, Digital Imagery and GIS with Census Mapping, Department of
Economic and Social Affairs, Statistics Division, New York
[2] United Nations (2000), Handbook on geographic information systems and digital mapping, Department of
Economic and Social Affairs, Statistics Division, New York
[3] Stern, M (1985) Census from Heaven?, Wallin & Dalholm Boktryckeri AB, Lund, Sweden
[4] GeoSpace International (Pty) Ltd (2005), GeoSpace International: List of Previous Projects, Pretoria, South


To top