United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Use of GIS and Web-based Mapping for Census Data Dissemination
United Nations Statistics Division
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Outline
UN Recommendations/Census Geography Programme
Building a Geographic Database
Digital Data Dissemination Strategies and Users
SALB Project
Handbook on Geospatial Infrastructure in Support of Census Activities
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Census Geography Programme: a continuous process
The recommendations derived from UN EGM and Workshops on GIS and census mapping emphasized the need for countries to consider the census geography programme as a continuous process, rather than the sequential mapping and dissemination operations.
It was also emphasized that the use of and application of contemporary geospatial technologies and geographical databases is beneficial at all stages of population and housing census process. Geospatial improve the efficiency in the preparatory, enumeration, processing and dissemination phases of the census
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Census Cycle
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
GIS with Census mapping at all stages
EAs Units Administrative and Reporting Units
GPS
Photo/Video GIS
Digital Mapping
Satellite Imagery
Pre-census Census Post-Census
GPS/PDA
GIS
Digital Mapping
GIS
Internet (Map-Server)
(Pre-enumeration) (Enumeration) (Post-enumeration)
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Administrative hierarchy
Every country has its own specific administrative hierarchy
Definition: A system by which the country and each lower level set of
administrative units (except the lowest) are subdivided to form the next lower level.
Administrative areas for which census data will be reported
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Illustration of a nested admin.Hierarchy
Relationships among all types of administrative and reporting unit boundaries are defined.
hierarchical levels may have actual administrative roles
Other units may have statistical roles alone
Provinces
Districts
Localities
Enum erationareas
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Coding Scheme
EA: a basic geographic feature Need for an identifier: linking the geographic feature to the
census data (attributes) recorded for them EAs and administrative units: coding scheme
A unique code assigned to each EA, used in data processing Coding scheme: scalability, flexibility, intuitiveness, compatibility
Example of a hierarchical coding scheme
province district locality Enumeration area
1 2 0 3 4 0 1 2 5 0 0 2 4
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Geocoding Concept
“Geocoding can be broadly defined as the assignment of a code to a geographic location. Usually however, Geocoding refers to a more specific assignment of geographic coordinates (latitude, longitude) to an individual address (UN Report of the EGM on Contemporary Practices in Census
Mapping and Use of GIS, 2007)
Geo-coding: not limited to address-matching
Geocoding covers a continuum of spatial scales: from individual housing units to enumeration area level up to higher administrative or national levels.
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Complete EA map with all components overlaid on one map display
358
M o llw e id e S tre et
361
378
374
349350
358
377
362
Enum eration Area Map Sym bols
Nationa l S tatistica l O ffice - Ju ly 1998Census 2000
EA
Locality
D istrict EA-Code
Hospital
Church
School
Buildingnumber
Province:D istrict:Locality:EA-Code:
CartaniaChartesMaptown
14032
022100361
500 100
Approximate scale
200m
N
4 5
1
2
3
4 56
7
1 2 1 3
891 011
1 4
1 51 6
1 7
1 8
1 9
2 0
2 12 2
2 3
2 42 5 2 6
2 72 82 9
3 0
3 13 2
3 3
3 4
3 5 3 6
3 7
3 8
3 9
4 04 1
4 2
4 3
4 4
4 54 64 7
4 8 4 9 5 0 5 1 5 2
5 35 4
5 5
5 6
5 75 8
5 9
6 06 1
6 2
6 36 46 5
6 6
6 7
6 8
6 9
7 0
7 1
7 27 3
7 4 7 5
7 6
7 77 87 9
8 08 1 8 2
8 3
8 48 58 6
8 78 8
1 2 3 4
9 1 0
1 2
7
891 011
1 2
1 3
1 4
1 5
1 6
2 1
2 2
2 3
2 4
2 5 2 6 2 7
3 2
3 33 4
1 9
2 0
2 1
2 22 3
2 82 9
3 0
3 13 2
3 3
4 1
4 2
4 3
5 0
5 1
5 25 4
5 8
5 9
2 7
2 8
3 1
3 7
3 8
4 2
4 3
4 44 5
5 1
4 34 0
4 14 2
6 15 7
5 85 96 0
6 5 6 2
6 36 4
1 9
2 02 1
2 2 3 1
3 2
3 33 4
3 5
4 14 24 34 4
1
2
34
5
6
1 0
11
1 2 1 3
1 8
1 9 2 02 1
2 72 8
2 9
1 7
Main components are:Street network, BuildingsEA boundaries layerAnnotation, Symbols, LabelsBuilding numbers Neatlines Legend
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Components of a Hypothetical urban EA map
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Implementation of an EA database
All large operational GISs are built on geodatabases;
Arguably the most important part of the GIS
Geodatabases form the basis for all queries, analysis, and decision-making.
A DBMS, or database management system, is where databases are stored.
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Entity-Relationship Example:
EA entity can be linked to the entity crew leader area. The table for this entity could have attributes such as the name of the crew leader, the regional office responsible, contact information, and the crew leader code (CL code) as primary code, which is also present in the EA entity.
Crew leader area
CL-code
Name
RO responsible
1-N
EA
EA-code
Area
Pop.
1-1
R
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Implementation of an EA database
: Example of an entity table – enumeration area
EA-Code
723101723102723103723201723202723203723204
…
Pop
763593838832632839388
…
CL-Code
88888888898989…
Area
32.128.419.134.625.728.312.4
…
Entity: Enumeration areas
Type (attributes)
Instances
Primarykey
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Components of a digital geographic census database
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Different Geographies
A geography for data collection: EA level or even dwelling level
Another geography for data dissemination: Aggregated level (confidentiality)
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Uses of Graphs: Enriching the Understanding of GIS Data Sets
Exploratory Spatial Data Analysis Linked Maps, Graphs & Tables Dynamic Feature Selection Animation Visualization over Time
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
GIS capabilities:Visualization
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Digital Data Dissemination Users
The wide range of potential users of disaggregated census data means that the NSO needs to pursue a multi-leveled digital data dissemination strategy.
Broadly, we can distinguish between the following types of users:
Advanced GIS users Computer literate users Novice users
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Internet Mapping: How it works
The server-side approach The client-side approach Hybrid approach
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Server-side approach
In server-side approach, the user sends a request for a map to the server holding the database. Mapping software on the server processes the request, produces a map—for example, in GIF format—and sends it back to the user.
Server-side approaches are good at providing access to relatively simple maps to a large, non-expert audience. They would thus be most suitable for a census
office’s presentation of census maps to the general public.
Client Server
request for map
map output
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Client-side approach
• In client-side approach, in contrast, most of the processing tasks are performed on the user’s (client’s) computer locally.
• Client-side approaches are preferable for Intranets, where a smaller number of users, with relatively comprehensive knowledge of GIS and mapping, access to complex databases. They would thus be suitable for in-house GIS data access for census office staff.
Client Server
request for map
data and applets
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Hybrid approach
•Combination of server - and client-side approaches.
•Combination of the advantages of client-and server-based strategies:
- They provide flexibility to the user in querying and manipulating maps locally, but transfer most of the processing load in demanding analysis tasks to the server.
- This requires some degree of communication between client and server concerning the available processing power.
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Web Mapping Architecture (Ref. B. Dickinson)
Mapping applications are accessed through standard web technologies to meet the needs of a specific business process or user.
Web ServicesWeb ServicesClients Data StoresKML/SOAP
KML/SOAP
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Web Map Services
A Web Map Service (WMS) is a standard protocol for serving georeferenced map images over the Internet that are generated by a map server using data from a GIS database. (developed by OGC)
WMS is a widely supported format for maps and GIS data accessed via the Internet and loaded into client side GIS software
Most GIS software support WMS
GIS APIs
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Cont…
Client technology: from “dumb” mapping to “smart” mapping application - The overall trend for web-based mapping is with more highly interactive, user-driven client interfaces as well as the desire by the general internet user to see the underlying data as a 3D environment and not a 2D flat-earth map.
Server-technology: service-oriented architecture (SOA) and broad spatial capabilities
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
The Second Administrative Level Boundaries data set project (SALB)
The Second Administrative Level Boundaries data set project (SALB) has been launched in 2001 in the context of the activities of the UN Geographic Information Working Group (UNGIWG) and has for objective to provide access to a working platform for the collection, management, visualization and sharing of sub national data and information in a seamless way from the national to the global level.
unsalb.org
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Handbook on Geospatial Infrastructure in Support of Census Activities (2009)
http://unstats.un.org/unsd/demographic/standmeth/handbooks/default.htm
United Nations Regional Seminar on Census Data Dissemination and Spatial Analysis
Amman, Jordan, 16-19 May, 2011
Conclusions
Consider the Census Geography Programme as a continuous process
Adapt best practices to suit specific census requirements
Partner with other stakeholders (the public and private sector) in order to Build the NSDI Work jointly on coding efforts Produce value added products – higher demand for census
data