united nations regional seminar on census data dissemination and spatial analysis amman, jordan,...

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



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



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



Census Cycle



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)



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



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



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



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.



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



Components of a Hypothetical urban EA map



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.



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



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



Components of a digital geographic census database



Different Geographies

A geography for data collection: EA level or even dwelling level

Another geography for data dissemination: Aggregated level (confidentiality)



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



GIS capabilities:Visualization



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



Internet Mapping: How it works

The server-side approach The client-side approach Hybrid approach



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



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



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.



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



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



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



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



Handbook on Geospatial Infrastructure in Support of Census Activities (2009)

http://unstats.un.org/unsd/demographic/standmeth/handbooks/default.htm



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



THANK YOU!

united nations regional seminar on census data dissemination and spatial analysis amman, jordan,...

Documents

census slide

census mapping

census data attributes

census cycle slide

housing census process

support of census activities

spatial analysis amman

dissemination phases