In Japan, GIS has been widely used in various
fields of administration such as city planning,
disaster protection planning, road maintenance,
water and sewage system management as well as
environment protection, and the standard of
GIS technology has been rapidly sophisticated
corresponding to the advancement of information
technology. Besides, an inter-ministry
meeting on GIS was established in the fiscal
year 1995 in order to promote development and
utilization of GIS in a comprehensive and integrated
manner.
Examples of GIS use in the field of statistics
are Census Mapping System (CMS) in the Population
Census, National Land Information System incorporating
various information related to the national
land, Farming Land Maintenance Geographical
Information System and so on. This paper
describes Census Mapping System (CMS) in the
Population Census.
1
Introduction
In the population censuses of Japan, Enumeration
Districts (EDs) have been established to define
the areas assigned to respective census enumerators.
The EDs have also served as units for compiling
small area statistics and as sampling units
for various sample surveys. However, the
boundaries of the EDs had not remained the same,
since the EDs had been demarcated for each of
the population censuses. This had made
time-series analyses of small area statistics
difficult. Moreover, the ED identification
codes given to each ED had not been systematic.
As a result, there had been limits to access
and to extensive use of the statistical data
compiled by EDs.
To overcome these limitations, a new unit-area
concept called Basic Unit Blocks (BUBs) and
an application system of GIS called the Census
Mapping System (CMS) were introduced in the
1990 population census. This paper presents
an outline of the BUBs and that of CMS, and
describes their utilization.
2
Introduction of Basic Unit Blocks in the 1990
Population Census
2.1 Basic Unit Blocks (BUBs)
In the 1990 population census, the concept
of BUBs as the permanent geographic unit was
adopted. For the areas where the "gaiku"
method on the basis of the law concerning address
designation of residence was employed for address
designation, one "gaiku" normally formed one
BUB. A "gaiku" is a small area permanently
established through partitioning a subdivision
(called "cho" or "aza") of a municipal
district by roads, railways, rivers, etc.
For the remaining areas, BUBs were demarcated
by the municipal governments on the basis of
the small areas similarly partitioned by geographically
clear and permanent characteristics and landmarks.
Ordinarily, a BUB includes approximately 20
to 30 households. The BUBs established
in the 1990 population census numbered approximately
1,606 thousand, covering the whole area of Japan.
The BUBs were used as the units for providing
small area statistics in the 1990 population
census, that is, fundamental tables were tabulated
and released by BUB.
2.2 Enumeration Districts
(EDs)
Each ED for the 1990 population census was
established so that it would contain the appropriate
number of households, ranging, in principle,
from 40 to 70. When a BUB itself included
enough households, it formed one ED. In
most cases, however, EDs were established by
combining two BUBs or more. When there
were a large number of households in such a
BUB with a high-rise apartment, two EDs or more
were exceptionally established by dividing it.
The number of the EDs established for the 1990
census is approximately 824 thousand.
Normally, one census enumerator was assigned
to each ED.
2.3 ED Maps and ED Lists
The BUBs and the EDs were established at
the same time, and maps showing their boundaries
(ED maps) and lists containing information on
each BUB/ED (ED lists) were prepared by the
local governments. The ED maps and the
ED lists were made through the following steps.
As basic maps to make ED
maps, existing maps are prepared on a scale
of 1:2,500, 1:5,000, 1:10,000, 1:25,000 or
1:50,000, including maps published by the
Geographical Survey Institute of the Ministry
of Construction and those for city planning.
Basic maps are modified,
as necessary, supplementing land readjustments,
road construction, river improvements and
landmarks after confirming current situations.
Field work was performed by each municipal
government for this purpose. Besides,
information showing characteristics of those
EDs is collected to make the ED lists.
BUBs and then EDs are established
based on the above information and their boundaries
are drawn on basic maps.
Original maps for ED maps
are made by appropriately cutting the basic
maps obtained through step iii) and by mounting
the map pieces on sheets provided by the Statistics
Bureau of the Management and Coordination
Agency, after deciding the region to be included
in each ED map. And then, the scale
of the map, the identification code of each
ED, the central point of population distribution
of each BUB and others are entered.
ED maps are completed by
photocopying the original maps on polyester
film sheets and by tracing the boundaries
of the BUBs and the EDs on them using specified
colors.
The ED lists are completed
based on the such data on each BUB/ED as the
identification code, the estimated number
of households and residents, the address,
and characteristics (e.g. whether a remote
area or not).
2.4 Modification
The BUBs and the EDs were established as
of October 1, 1989. Whenever their modification
became necessary, they were altered. The
number of the ED maps is approximately 46 thousand,
and the number of EDs contained in each ED map
ordinarily ranges between 10 and 20. (The
numbers of the BUBs and the EDs in the paragraphs
2.1 and 2.2 are those after the modifications).
3
Introduction of Census Mapping System in the 1990
Population Census
3.1 Introduction
of Census Mapping System (CMS)
Along with the establishment of the BUBs
in the 1990 population census, the Statistics
Bureau developed CMS utilizing GIS technology
to enable more sophisticated use of statistical
data and the geographical information on BUBs.
3.2 Functions of CMS
The major functions of CMS are storing and
maintaining information on position coordinates
of the BUBs/EDs' boundary lines, and enabling
compilation of such small area statistics as
those by "cho"/"aza". Another important
function of CMS is to show various kinds of
small area statistical data in the form of maps
through a screen and a electrostatic color plotter.
3.3 CMS Data Stored
in the 1990 Population Census
The data stored in CMS in the 1990 population
census are as listed below. They can be
divided into the two categories of feature data
and attributive data.
[Feature data]
Shapes and position coordinates
of BUBs/Eds
Shapes and position coordinates
of rivers, lakes and ponds
Central point position
coordinates of BUB population distribution
[Attributive data]
Tabulation results of the
1990 population census by BUBs
Data on BUBs including
ED identification codes, BUB identification
codes
3.4 Input of Feature Data
The feature data were input using the ED
Maps by a hand-digitizer during the period from
the beginning of 1991 to the end of 1993.
Since the ED Maps do not include information
on absolute position coordinates (longitude
and latitude) which ordinary maps do, it is
impossible to read the position coordinates
directly from the ED maps. Therefore,
relative position coordinates were input for
each ED map, and were then converted to absolute
position coordinates by taking correspondence
through some points between the ED map and a
map with longitude and latitude information.
After conversion, the absolute position coordinates
were combined municipality by municipality.
4
Maintenance of BUBs and CMS Data in the 1995 Population
Census
4.1 Maintenance of BUBs
As the way of establishing the BUBs shows,
they have a permanent nature. In the 1995
population census, however, some of the BUBs
established in the 1990 population census were
altered due to such inevitable reasons as boundary
changes between municipalities and changes in
address designation. Therefore, the BUBs
established in the 1990 population census were
reviewed in the 1995 population census and some
of them were altered when necessary. Through
these alterations, the total number of the BUBs
after the 1995 population census became approximately
1,740 thousand.
Based on these BUBs, EDs for the 1995 population
census were established in the almost same way
as described in paragraph 2.2. The EDs
for the 1995 population census numbered approximately
882 thousand.
4.2 Computerized
Preparation of ED Maps
As the feature data stored in CMS do not
include such detailed background data as those
on roads and public facilities, ED maps cannot
be directly obtained using CMS. Accordingly
ED maps for the 1995 population census were
prepared following the procedures described
in paragraph 2.4 in most municipalities.
On the other hand, as there are a number of
local governments developing their own GIS's
with the necessary background information for
administrative purposes such as city planning
and water and sewage system management, the
ED maps are obtained by updating the feature
data for 1990 population census based on this
background information. Approximately
a quarter of all ED maps were computerized by
the following procedure in the 1995 population
census.
The 1990 feature data in
CMS were output onto magnetic tapes and sent
to local governments.
The feature data in CMS
were combined with background data which local
governments possessed in their GIS's, and
then basic ED maps for ED maps were made by
computers.
Local governments made
necessary modifications on the basic maps
including demarcation of BUB/ED boundaries
after field work. And then the new ED
maps for the 1995 population census were made
by computers. At the same time, the
magnetic tapes containing the updated CMS
feature data were prepared.
The magnetic tapes with
the updated data for the 1995 population census
as well as the reproduced ED maps were sent
to the Statistics Bureau.
4.3 Computerized Compilation
of ED Lists
In the 1995 population census, updating of
ED lists by municipal governments was newly
done using personal computers. The information
for ED lists of the 1990 population census was
output onto floppy disks and sent to municipal
governments through prefectural governments.
The municipal governments updated the contents
of the floppy disks after performing field work
for the 1995 population census. The floppy
disks were sent back to the Statistics Bureau.
This method was expected to reduce the workloads
of local governments, since the characteristics
of the BUBs should not change greatly in a five-year
term.
5
Expansion of CMS Use in the 2000 Population Census
In the 1995 population census, the production
of ED maps were automated for seven major cities
by using the GIS that the respective cities
had developed for their own purposes.
In the 2000 population census, 15 major cities
are supposed to computerize the production of
their ED maps (40% of all EDs in Japan).
6
Use of CMS
6.1 Use of CMS for
Demarcation of DIDs
Densely Inhabited Districts (DIDs) were introduced
to demarcate urbanized areas since rural areas
were absorbed into cities through the integration
policy of cities, towns and villages during
1950's. In the 1995 population census,
CMS played a very important role in the work
of demarcating DIDs.
DIDs have been designated by the Statistics
Bureau in every population census since 1960.
Statistics for DIDs and their area demarcation
are used for various official and analytical
purposes, e.g. for grant fund allocation from
the national government to local governments,
for urban planning, etc. A DID is defined
as a contiguous area of BUBs whose population
density at the BUB level is 4,000 persons/km2
or more, and whose total population is 5,000
persons or more.
To demarcate the DIDs and prepare the maps
showing the boundaries of the DIDs, it was necessary
to do the following mostly manually.
To measure the area of an
ED and calculate its population density
To measure the percentage
of area of urban facilities in an ED
To calculate the sum of
the population counts of the contiguous EDs
with a high population density or with a high
rate of area of urban facilities
To calculate the population
density of a demarcated DID
To transcribe the boundary
lines of the DIDs onto maps on a scale of
50,000
By demarcating DIDs on the basis of BUBs utilizing
CMS, steps corresponding to those of i) through
iv) above were mostly automatically performed
by the CMS in the 1995 population census.
6.2 CMS for Production
of Grid-Square Statistics
CMS has also contributed to reducing the
workload of production of grid-square statistics
and thus speeding up its release by almost six
months. Grid squares are areas of 1km
squares uniformly defined for the whole country
on the basis of longitude and latitude lines.
Grid-square statistics are compiled from ED
statistics by establishing correspondence between
EDs and grid squares.
In the past population censuses, the work to
establish correspondence between EDs and grid
squares required quite a great deal of manpower
as the work had been manually done. But
because the correspondence between EDs and grid
squares was established by CMS automatically,
the manual workload was significantly reduced
in the 1995 population census.
6.3 Comparison of Boundaries
of EDs between Censuses
To reduce the response burden of various
sample household surveys, the Statistics Bureau
makes it a rule to avoid selecting the same
EDs as sample areas in different statistical
surveys within a certain period of time.
For example, in the Family Income and Expenditure
Survey, the sampling method is designed so that
the same ED may not be selected twice within
a period of five years or less.
For this purpose, correspondence of the EDs
between two censuses is required. This
work had been made by manually comparing ED
maps of two population censuses. In the
1995 population census, the boundaries of EDs
in 1990 and 1995 were compared by CMS, and the
correspondence list of EDs between two population
censuses was made automatically.
6.4 Expansion of CMS to
Cover the Establishment and Enterprise Census
Application of GIS in production of statistics
is not limited to the population census, but
extends to other censuses. The most important
one is the establishment and enterprise census.
Traditionally, the EDs of the establishment
and enterprise census have been demarcated independently
from those of the population census, because
the geographical distribution of households
and establishments is quite different.
However, as the BUBs adopted in the population
census are relatively compatible or homogeneous
with the EDs of the establishment and enterprise
census, it became possible in the 1996 establishment
census to establish close linkage between the
BUBs and the EDs of the census. By integrating
the data of the EDs of the establishment and
enterprise census into CMS, the capabilities
of CMS will be greatly enhanced.
As small area data on both households and establishments
can be used in combination (e.g. for computing
the day-time population), there will be more
applications of CMS for various purposes.
6.5 Dissemination of Small
Area Statistics with CMS Data
From the 1995 population census on, use of
small-area statistics of the population census
has become easier than before owing to CMS.
In the past, the information of locations of
EDs could not be easily disseminated, because
ED maps were large and voluminous. But
the CMS data on locations of BUBs and EDs can
be disseminated via computer files.
In the 1995 population census, the following
machine-readable files containing geographic
reference information have been disseminated:
i) boundaries of BUBs, ii) correspondence
between BUBs and cho-aza (area section) names,
and iii) the longitude and latitude of the central
point of BUB. For statistical users with
a good GIS expertise, the data of the boundaries
of BUBs will be most useful for identifying
the locations. For statistical users without
GIS, the cho-aza names file will be a simple
but useful tool to identify the locations of
BUBs.
