a geo-referenced census frame of dwellings for the 2011 census...
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Innovative Methodologies for Censuses in the New Millennium, a satellite meeting of the 56th
session of
the ISI, 31 August – 2 September 2007, Southampton, UK
Sharthi Laldaparsad, Republic of South Africa, Statistics South Africa, Geography Division page 1 of 8
A Geo-referenced Census Frame of Dwellings for the 2011
Census of the Republic of South Africa
Sharthi Laldaparsad
Statistics South Africa, Geography Division
Abstract For the first time in the South African census taking history, Statistics South Africa (Stats
SA) is recording and using the position of every dwelling in the country in its preparation
towards Census 2011. Such a frame of dwellings is not available in the country, and there
is no address register, with many rural dwellings not ever having been assigned an
address. The statistics office has prioritised the creation of a geo-referenced dwelling
frame in preparation for and monitoring of operations, to ensure that all dwellings in the
country are covered during enumeration. The longer-term vision is to establish a
continuously maintained geo-referenced register of dwellings, establishments and
buildings.
The reliance on partnerships with other national government departments and agencies,
as well as local authorities, is key to the initiative. The development and maintenance of a
dwelling frame is of great interest to various government role players, as an enabler of
physical service delivery, emergency response services, billing systems, property
valuation rolls and financial services to citizens. In areas where addresses are available,
such as large urban areas, the dwelling frame will integrate, standardise and continuously
keep updated such a frame by partnering with local municipalities as data custodians.
The methodology to geo-reference dwellings makes use of high resolution aerial
photography and satellite imagery. This imagery is acquired through cost-sharing
arrangements with other government departments. An office exercise takes place to point
capture each dwelling from the photos using a Geographical Information System (GIS),
followed by a field exercise to verify points and capture new points using Global
Positioning System (GPS) technology, as well as capturing of about 18 attributes on each
built structure. This information is then integrated into the organisation’s spatial database
and updated on the website.
The attributes of each dwelling which are captured cover elements of what would be
included in a housing census, and the possible contribution of the dwelling frame to the
collection of information usually undertaken in a census of housing is being explored.
Since the characteristics and locations of establishments and other buildings (e.g. schools,
clinics, etc.) are also recorded during the capturing of dwelling units, the frame can be
explored as a source for other statistical collections, such as information on informal
businesses, as well as in the compilation of building statistics.
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Innovative Methodologies for Censuses in the New Millennium, a satellite meeting of the 56th
session of
the ISI, 31 August – 2 September 2007, Southampton, UK
Sharthi Laldaparsad, Republic of South Africa, Statistics South Africa, Geography Division page 2 of 8
Background In our strategy to ensure complete coverage for the 2011 Census of Population and
Housing for South Africa and in our attempts to minimise census undercount, right from
the beginning of the census process, from the foundation phase of a census, that is, the
delineation of the country into census enumeration areas and easily understandable
cartography that enables clear boundary identification and mobility throughout the
country, Stats SA has embarked on the development of a Geo-referenced Dwelling
Frame.
The objectives of the Geo-referenced Dwelling Frame is to identity or locate and describe
all structures on the ground with an exact coordinate and supporting descriptive attributes
about the structure. The project includes the continuous maintenance of such a frame that
can be used for subsequent censuses and surveys.
The Geo-referenced Dwelling Frame started with the main focus on allocating addresses
to about 50% of the country’s residents that have no addresses - mainly in the former
homelands of South Africa. (As shown in the picture below the dwelling received
numbers from each of the different service providers, even Stats SA during the censuses
spray-painted numbers on the wall.)
The project was piloted in 2002 in the village of Botseleni in the province of Limpopo
where dwellings were geo-referenced and addresses were for the first time displayed on
homesteads. The project is gaining momentum and the target is to complete the entire
country by October 2009, in time for the 2011 Census Pilot.
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Innovative Methodologies for Censuses in the New Millennium, a satellite meeting of the 56th
session of
the ISI, 31 August – 2 September 2007, Southampton, UK
Sharthi Laldaparsad, Republic of South Africa, Statistics South Africa, Geography Division page 3 of 8
Methodology The project is divided into two parts, namely formal (areas where formal addresses exist,
linked to formal cadastre and property title deeds); and informal (areas where no
addresses exist, nor formal cadastre or title deeds).
For formal areas, address databases from local municipalities, cities, large towns and
metropolitan councils are received and compared with the 2001 Census dwelling unit
count and latest aerial photography. So far there are 2 050 956 dwellings from all six
metropolitan councils. We intend setting up memorandums of understandings (MoUs)
with local municipalities, cities, towns and metropolitan councils for the continued
maintenance of this data. The picture below shows a typical formal area, with aerial
photography, cadastre and dwelling points, which in this case has formal addresses linked
to street names and suburbs.
For informal areas in the country and areas with no information, aerial or satellite
photography is acquired, an office exercise to put points on each dwelling takes place,
then fieldworkers go into the areas to verify the point and collect the attribute data. A
digital photograph of the dwelling is also taken. (As shown in the pictures on the next
page.) Stats SA further conducts a 100% office quality assurance and a 3% field sample
quality assurance on the data.
-
Innovative Methodologies for Censuses in the New Millennium, a satellite meeting of the 56th
session of
the ISI, 31 August – 2 September 2007, Southampton, UK
Sharthi Laldaparsad, Republic of South Africa, Statistics South Africa, Geography Division page 4 of 8
-
Innovative Methodologies for Censuses in the New Millennium, a satellite meeting of the 56th
session of
the ISI, 31 August – 2 September 2007, Southampton, UK
Sharthi Laldaparsad, Republic of South Africa, Statistics South Africa, Geography Division page 5 of 8
How census benefits
Updating and correcting the ‘place name’ database
During Census 1996 Stats SA developed a place name database. This is a database of
community names and its geographic extent (namely suburbs, towns, cities, villages,
etc.).The database was updated using limited administrative data and photography for
Census 2001. Information from the Geo-referenced Dwelling Frame now enables us to
update the place names database further. The picture below shows the different villages
as captured for each point on the Dwelling Frame. In this way the census output
geography for small areas is updated and corrected, reflecting a more realistic picture of
the situation on the ground.
Demarcation of Enumeration Areas
The delineation of enumeration areas (EAs) is made simpler. EAs will be split or
aggregated. In certain cases, portions of EAs will be dissolved or added to EAs according
to an EA size criteria based on the amount of dwellings.
-
Innovative Methodologies for Censuses in the New Millennium, a satellite meeting of the 56th
session of
the ISI, 31 August – 2 September 2007, Southampton, UK
Sharthi Laldaparsad, Republic of South Africa, Statistics South Africa, Geography Division page 6 of 8
Other areas of use for the census:
• A stable frame of dwellings will be provided as lists for the enumeration phase. If EA boundaries are unclear (e.g. cutting through houses), the fieldworker refers to the list.
This limits the risk raised during previous censuses on poor EA boundaries that don’t
follow physical features.
• Monitoring of census enumeration per dwelling and ensuring as a minimum a questionnaire is returned for each dwelling point i.e. monitoring non-response per
dwelling and targeting dwellings for re-visits. This enables spatial monitoring,
tracking of progress and targeted remedial actions.
• Reconciliation can be done at the end to determine if all dwellings have been accounted for. Through its geographic identification duplicate data and missed data
can be identified.
• Internet options for completion of census questionnaires online can be built more confidently linking data directly to its geographic location.
• Knowing the exact location of each dwelling from which information is collected enables us to define areas for which aggregates are provided independently from the
collection unit (i.e. EAs).
• The rationalisation of the country’s main geographical areas (i.e. provinces, district councils, municipalities) can be done more correctly at a dwelling level.
• A continuously maintained Dwelling Frame can be used to estimate statistically the population of the country, this is especially needed since South Africa has moved
only recently to 10 yearly population censuses and more frequent data is still
required.
• The Dwelling Frame could substitute the Housing component of the Census of Population and Housing thus resulting in a shorter more focused population
questionnaire, which in most cases leads to better quality data.
-
Innovative Methodologies for Censuses in the New Millennium, a satellite meeting of the 56th
session of
the ISI, 31 August – 2 September 2007, Southampton, UK
Sharthi Laldaparsad, Republic of South Africa, Statistics South Africa, Geography Division page 7 of 8
How statistics in general benefits Our vision is that the Dwelling Frame becomes the frame for all household based
censuses and surveys. By having an updated dwelling frame more accurate samples for
surveys can be drawn and improved data collection is envisaged.
Changes to the country’s official political boundaries puts great stress on census and
survey data, to continuously keep the both in synch and back tracking of time series data
for comparison purposes. Having exact dwelling locations, data can be provided with
greater accuracy for frequently changing political geographies.
The Dwelling Frame provides characteristics and locations of other structures (see table
below an example for one municipality). Information on the number and location of other
structures is beneficial for statistics related to education, health, policing, businesses, etc.
and improved service delivery, which goes beyond the scope of its planned use by us.
MNQUMA (EC122)
FEATURE USE Traditional
Urban
Formal
Urban
Informal
Rural
Formal TOTAL
Bank 0 4 0 0 4
Bottle Store 10 6 0 0 16
Business 62 209 10 1 282
Church / Place of Worship 386 40 15 1 442
Day Clinic 22 6 0 0 28
Demolished Structure 3,008 59 59 23 3,149
Dwelling Unit 51,548 6,520 3,400 293 61,761
Factory 0 37 1 0 38
Filling Station 3 7 0 0 10
Garage 1 3 0 0 4
Guest House / Lodge 1 6 0 0 7
Market 1 0 0 0 1
New Dwelling Under
Construction 1,993 347 87 22 2,449
Offices 18 37 6 2 63
Other 152 29 7 15 203
Sports, Oval, Stadium 1 4 0 0 5
Park 0 1 0 0 1
Police Station 2 5 0 0 7
Post Office 9 5 0 0 14
Holiday Home 58 47 0 0 105
Residential Hotel 1 9 0 0 10
School 472 52 5 5 534
Convent/ Monastery/
Religious Retreat 1 0 0 0 1
Old Age Homes 0 1 0 0 1
Hospital/ Frail Care
Centre 1 2 0 0 3
Initiation School 63 0 0 0 63
Prison/ Correctional 0 2 0 0 2
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Innovative Methodologies for Censuses in the New Millennium, a satellite meeting of the 56th
session of
the ISI, 31 August – 2 September 2007, Southampton, UK
Sharthi Laldaparsad, Republic of South Africa, Statistics South Africa, Geography Division page 8 of 8
Institution/ Police Cells
Boarding School Hostel 1 0 0 0 1
Student's Residence 1 40 0 9 50
Workers Hostel 28 28 9 0 65
Shop 406 29 6 0 441
Storage Room 26 1 1 0 28
Vacant Dwelling 6,432 208 509 64 7,213
Vacant Stand 0 192 0 0 192
TOTAL 64,707 7,936 4,115 435 77,193
Conclusion
The Dwelling Frame has enormous possibilities to improve and maybe fundamentally
change the conventional census and survey methodologies used by a statistical agency.
Register-based information from the Business Register, Population Register and the
Dwelling Frame (National Address Register) are the pillars and the future direction for
statistics. In addition the National Address Register gives the other two a sense of
location.
Through the Dwelling Frame unaddressed communities are identified and addressed.
Having an address is close to the hearts of the people of our country, it’s certainly seen as
a community driven project by engaging the local structures and community members,
contributing to the growth of the second economy in South Africa.
Its continued maintenance is important since its relevance goes beyond that for only
statistical purposes, to that of common infrastructural framework information for nation
building and inter-departmental support is crucial.
Acknowledgements
I would like to acknowledge the contributions made by all pioneers and current staff
members of the Address Project and Dwelling Frame Project from both within and
outside Stats SA.
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