GIS and The Population and Household Census in Israel
From Present to Future
Dafna Amar, Shahar Katz
GIS Division
Israel Central Bureau of Statistics
Keywords: Population and Household Census, Integrated Census, Spatial Analysis.
Abstract
In this paper, we would like to show how the role of GIS has evolved, following the change in perception between the past 1995 Population and Household Census, and the up-coming census in 2006.
In the 1995 census, for the first time, GIS technology incorporated into the census process. The preliminary goal of integrating GIS in the census was to improve the enumeration process. Producing detailed maps and address files for the enumerators, an aid for fieldwork management, and enabling full coverage of the buildings enumeration, helped to solve some of the main difficulties of population censuses.
During the establishment and implementation of GIS, more advantages of GIS technology were recognized and used, for the census benefit. A redistricting application was used to create the enumeration areas. The by-product was anchoring census data to geographical addresses and to building level. Thematic maps and other cartographic products were created, using GIS tools for geospatial analysis.
These uses of GIS, although limited, brought to light the importance of GIS for the census.
The most prominent change in the frame development for the 2006 census is the transition from a traditional household enumeration census, to an “Integrated Census”. The integrated census combines two methods of conducting a census: an administrative census based upon official registers and other national files, and supplementary sample surveys, as strictly a support methodology.
Those changes encourage a more advanced use of GIS that better captures the essence of the methodology of spatial analysis. The GIS will play a major role in the up-coming census.
The 2006 integrated census
The 2006 census will be fundamentally different from the previous census.
Throughout the time between the two censuses, drawing the conclusions of the latest and establishing goals for the next, an important issue has emerged:
A substantial part of the information, which needed major effort to achieve in the previous census, is currently available. Many organizations such as government authorities and public companies spend a lot of time and resources into collecting and updating such data that the census can use.
The new method of conducting the census will lead to important improvements. The time between the census and the publication of the findings will substantially reduce. The gap between censuses will also get shorter. The census data can be available faster and to a much larger audience.
Countries, especially in northern Europe intend to adopt similar methodologies and transfer from a traditional census to an integrated one, relying on administrative data sources available at different authorities.
The main problems of such a process are:
1. The goals and methods of data collection are different from one organization to another.
They do not necessarily match the census needs.
2. There is no standardization in files format, data format, integrity of data, and data updates.
Therefore, the data obtained for the next census will be in various forms, unlike the previous census, where all the data input passed through the “filter” of a standard questionnaire. The level of update was all relative to the day of the census.
In the up-coming census, the data will be a combination of integrated records from different sources combined with input of direct enumeration in sample surveys.
Depending on existing data, the census faced with new types of problems, one that calls for new frame development. As data is collected and integrated long before the day of the census, some of the problems can be identified and dealt with ahead of time. At present, four years prior the next census, methodologies designed for all the process stages. Experimental prototypes, using examples of real data have already started, receiving the data samples, editing, and integrating them with other data sources.
The use of GIS in the integrated census
GIS will serve in most of the crucial stages of the 2006 census; in the pre-census process, through the process of enumeration, and in the analysis and dissemination of census results. Here are the unique functions of GIS in the stages of the census process:
1. Geo-processes for data integration.
2. Spatial database and Metadata.
3. Tracking areas with missing data.
4. Complimentary data production.
5. Sampling.
6. Management & control of field supplementary enumeration.
7. Spatial analysis methods for querying census data.
1. Geo-processes for data integration.
In 1995 census, address matching of census questionnaires to GIS addresses was a complicated process, completed following the census. The result was that each respondent was linked to an address and each building (with unique-identifier UID) linked to the population with its census characteristics. The experience in record linkage process, together with the updated coverages will provide the basis to the next census.
In the 2006 census, the previous census data will be only one source among different national files that will have to be linked together. Each source file will have a spatial connector key to anchor its data to space (coordinates, address, parcel, etc). Geography will be the connecting dimension between different types of data. The differences in the spatial key will result in a two-stage process:
i. Connecting data with the same spatial anchor (address, parcel, water pipe, etc) with the process of geocoding.
ii. Connecting data with different spatial anchors (address within a parcel, water pipe in distance from a building, etc) by geo-processes between different data coverages.
This is a unique function of GIS, the census will rely upon in records linkage with unrelated field.
2. Spatial database and Metadata.
After ensuring, the integrity of the data in terms of accuracy, completeness and scope, preliminary spatial database was created for the 1995 census. Based on the most detailed level of spatial anchor: a full country cover of address and buildings. That spatial database offer the possibility to get out from the traditional borders of statistical areas, and the ability to aggregate data depending on the need, the subject, or by the result of analyst process. Completely new opportunities of research, analysis and publication of the census data opened. The layers created for the census updated and for the 2006 census, we attend to transfer the data to the platform of Esri’s spatial database engine – ARCSDE with ORACLE database.
The GIS-census spatial database should create and store Metadata together with the data. The Metadata should include definitions of the data fields and tables, the data sources and much more information that will be easy to query and search. Creating new standards and work methodology to be implemented in the regular work of the national statistic bureau, should be one of the main advantages of this census.
3. Tracking areas with missing data.
The anchoring of data in space will create a continuous data blanket. With the visualization of data, it will be easy to allocate holes in the cover and identify data deficiencies. Digital maps, aerial photographs and field surveys, before the census, will complete the geographical updates.
4. Complimentary data production.
After identifying data deficiencies, spatial analysis methods can complete missing data, using interpolation. Methods like grid or spatial interpolation can create data, based on the existing data, with analysis of variance and other statistical components. The results will allocate areas that needs sampling for the enumeration completion.
5. Sampling.
Selecting representative samples from the population for field interviews is a complex task. A two-step process determines the specific individuals that will be interviewed: choosing the areas to sample and choosing specific households from within those sample areas to interview. With the continuous coverage of spatial demographic information, GIS tools will be ideal for this task.
6. Management & control of field supplementary enumeration.
In the 1995 census, the use of GIS significantly improved the fieldwork during the census. The fieldwork benefited mainly from two GIS products: printed maps and address files. Through mostly automated process, the GIS created maps for all the various levels of workers and management.
The address files were used for controlling the enumerator’s work, by giving the supervisor a tool for monitoring the enumerator’s work, in quality and rate.
Both GIS products helped ensure the full coverage of population in the census.
In the 2006 census, we will integrate GIS with the computerized field work system to improve on-line management and control on the process of sample enumeration. New buildings found in the field can be updated on-line directly into the spatial database. Collected data can immediately be linked to the address of the household so there will be no need for post-census long and difficult process of anchoring the data back to the GIS. Direct data transfer will help locate and follow each enumerator, including on-line checking of the timing and quality of work. Operational problems can be identified quickly and appropriate actions in real-time can be taken to resolve them. The entire process and the exact technical aspects are still in the initial planning stages.
7. Spatial analysis methods for querying census data.
Spatial analysis can offer the census new ways to investigate data. Sometimes the only connection between two phenomena is their location in space. GIS can be a tool for data mining and even creating new, unique information. Spatial methods like buffering, finding distance between items, phenomena that expand in space and density of characters in a spatial unit. These types of queries are the essence of GIS. First use of these methods was done in investigating the 1995 census data. The 2006 census can help to establish a new framework, making GIS methods a real, independent research tools for use in the publication of the national statistics.
Summary
The first steps integrating GIS with the census at the Israel Central Bureau of Statistics (ICBS) were made in the 1995 census. All the census stages benefited from a very successful experience. Some of the processes designed and implemented back then, like redistricting, linkage of GIS address and census data, management of field work, and thematic maps publication, will serve us with improvements, for the next census.
In the 2006 census, the ICBS will take this success even further. The power of GIS will be used to enter new fields in the processes of integrating data, analyzing data, sampling data and disseminating the census data in new ways.
Shahar Katz
Director, GIS Division
Telephone: 972-2-6592158
Fax: 972-2-6592103
E-mail: shahar@cbs.gov.il
Dafna Amar
System Administrator,GIS Division
Telephone: 972-2-6592154
Fax: 972-2-6592103
E-mail: dafnab@cbs.gov.il
Central Bureau of Statistics
P.O.Box 34525 Givat Shaul,Jerusalem 91342
Israel