use of geographic databases (maps) and other geospatial tools

UNSD-CELADE Regional Workshop on Census Cartography for the 2010 Latin America’s census round

Use of geographic databases (maps) and other geospatial tools

during the census


Overview

Introduction:From EA creation to EA map production for enumeration

Stages in quality control, EA map production and Database maintenance

IntroductionQuality controlEA map productionDatabase maintenance

Other geospatial toolsGIS for logistics and EA managementPDAs with GPS

Conclusion


Introduction

Accuracy and completeness of census data depend substantially on the quality of the cartographic base maps used by enumerators

A continuous process of quality control and quality improvement during data conversion allows review of all map products before distribution to enumerators.

This involves verification of the correctness of administrative boundaries by local administrators

Remaining problems and inconsistencies must be resolved before the final products can be generated.


Stages in quality assurance, output production and database maintenance

Quality control /Quality management

EA map production

Incorporate last-minute administrativeboundary changes

Verify match betweengeographic dataand attributes

Develop andimplement databasemaintenanceprocedures

Resolve problemsand make finalchanges

Develop enumerator guidelines and training materials

Join geographic boundary files andattribute database

Complete andverify meta-database

Production of enumerator andsupervisory maps

Distribute maps for verification by local administrators

Verify logical and

positional accuracy

completenessand

Database maintenance


Quality Control (component of quality assurance)

Quality control refers to a final check of the digital map database before the products are released for the census operation

Normally consists of software and manual checks- some to be performed on all products, while more complex and time consuming checks are done on a subset of products using an appropriate acceptance sampling strategy

Final quality assurance is best performed using printed hardcopy maps.


Verification

Match between geographic data and attributesCorrectness of the match between boundary data and attribute data

There should at least one map feature (a point, line, polygon) for each record in the geographic attribute table

Verification of several aspects of database integrityVerification by census cartography staff will involve the inspection of the following acceptance criteria:

Legibilitysequence of data layers drawn on a mapMap scale Source and copyright information


Quality Control (cont.)

Verification by local authorities and final administrative unit check

These boundaries change often, with new states, provinces, and districts added on a regular basis irrespective of census-taking effortsIdeally administrative boundaries are frozen by government decree several months before the census

Several options for dealing with this problem closer to the time of the enumeration include:

continuous trackingboundary changes are announced in advancedetermine a freeze date


Quality Control (cont.)

If administrative boundary changes continue to occur, then continuous tracking before the census is an option. As changes occur, they are immediately committed to the digital map database.

In some countries, boundary changes are announced in advance. The census mapping agency can thus schedule work on those areas for a later stage in the census mapping process;

The final option is for the census mapping agency to determine a freeze date and to revise all boundaries at a later stage, possibly after the census has been taken.


EA map production (including map printing)

Production of enumerator and supervisory mapsThis can be done at the main NSO location or in regional field offices, depending on the type of NSO organizational structure

Develop enumerator/supervisory guidelines and training materials

Anyway, they should be simple, but contain enough information to allow easy orientation


EA Maps should contain the following information:

Entire enumeration area defined by a clearly indicated boundary line

Some parts of the neighboring areas and other geographic text and information to facilitate orientation

Features for EA maps should include:streets and roadsbuildingslandmarkshydrological featuresother notable or relevant features, possibly including topography, water bodies, etc; and

A consistent map legend or map key, including the exact names and codes of the administrative and enumeration zones, a north arrow, a scale bar, and a legend explaining the symbols used for geographic features

Components of a Hypothetical urban EA map

Annotation and symbols

361

378

374

349350

358

377

362

BoundariesStreet Network Buildings

1

2

3

4 56

7

12 13

891011

14

151617

1819

20

2122

23

24 25 26

272829

30

31 3233

34

35 36

37

38

39

4041

42

43

44

454647

48 49 50 51 52

5354

55

56

5758

59

6061

62

636465

66

67

68

69

70

71

7273

74 75

76

777879

80

81 82

83

848586

8788

1 2 3 4

9 10

1 2

7

891011

12

13

14

15

16

21

22

23

24

25 26 27

323334

19

20

21

2223

2829

30

3132

33

41

42

43

50

51

5254

58

59

27

28

31

37

38

42

43

4445

51

4340

4142

61 57

585960

65 62

6364

19

2021

22 31

323334

35

41424344

1

2

34

5

6

10

11

12 13

18

1920 21

2728

29

358

Enumeration Area Map Symbols

National Statistical Office -J l 1998

Census

EA

Locality

District EA-Code

Hospital

Church

School

Buildingnumber

Province:District:Locality:EA-Code:

CartaniaChartesMaptown

14032

022100361

Approximate scale

N

45

17

Building numbers Neatlines and legend

Complete EA map with all components overlaid on one map display

358

Lambert Avenue

Mercator Avenue

Cassini DriveCassini Drive

Imhof Drive

Eckert Drive

Miller

Drive

Bonne Street

Mollweide Street

Grinten S

treet

Goode

Street

Bessel Street

Street

Robinson Street

Tissot Street

Gall StreetP

tolemy S

treet

Ortelius Street

Clarke Street

Tobler StreetSnyder Street

Krassowskij Street

361

378

374

349 350

358

377

362

Enumeration Area Map Symbols

National Statistical Office - July 1998Census 2000

EA

Locality

District EA-Code

Hospital

Church

School

Buildingnumber

Province:District:Locality:EA-Code:

CartaniaChartesMaptown

14032

022100361

500 100Approximate scale

200m

N

45

1

2

3

4 56

7

12 13

891011

14

151617

1819

20

2122

23

24 25 26

272829

30

31 3233

34

35 36

37

38

39

4041

42

43

44

454647

48 49 50 51 52

5354

55

56

5758

59

6061

62

636465

66

67

6869

70

71

7273

74 75

76

777879

8081 82

83

848586

8788

1 2 3 4

9 10

1 2

7

891011

12

13

14

15

16

21

22

23

24

25 26 27

323334

1920

21

2223

2829

30

3132

33

41

4243

50

51

5254

5859

27

28

31

37

38

42

43

4445

51

4340

4142

61 57

585960

65 62

6364

19

2021

22 31

323334

35

41424344

1

2

34

5

6

10

11

12 13

18

19 20 21

2728

29

17

Main components are:Street network, BuildingsEA boundaries layerAnnotation, Symbols, LabelsBuilding numbers NeatlinesLegend


EA map production (including map printing)

Other Critical FactorsBarcoding

Many barcode readers now come with a USB interface with a decoder either integrated into the unit or separateThe NSO can use preprinted barcode labels or use software that creates a barcode for each map produced

Black and White Good black and white maps can also be photocopied without loss of information which allows the local staff to produce additional copies of EA maps as required.

Design based on users experience, keep backup copies, automate printing


Database maintenance

The census cartographic staff should collect the EA maps after the census and follow-up on any suggested revisions through an established procedure of incorporating edits into the master geographic census database

This may require making the corresponding corrections in the digital census database, or it may require some additional fieldchecking, or accessing satellite or aerial photo data to verify changes.

This can be a very involved process but can ensure that the NSO holds the most current information on the enumeration areas, which will reduce the workload for cartographic activities before future censuses or surveys.

It should not, however, delay the release of census results.


Database maintenance:

Census mapping office should implement database maintenance procedures immediately following a census

continuous updating of boundaries and other features as new information becomes available

During the intercensal period, a clear system of version control should be implemented

Changes implemented in the database should be documented and published. For instance, only one or a small group of staff members should have the authority for committing changes to the master database.


Database maintenance:

Staff continuity is critical The census office needs to identify a core staff that will maintain the database in the intercensal period, provide geospatial services for other statistical applications such as sample surveys, and serve as an institutional memory This will facilitate a smooth operation of census GIS applications in the next enumeration

Think long-termThe benefits of a digital geographic census program will outweigh the considerable costs, but only if the resulting census database is used for many applications beyond the core tasks of a census


Use of Geospatial Tools during the census

Support logistical planning and monitoring of census progress Perform real-time or near real-time quality control of the census database

Common Geospatial Tools Used During the Census

GIS for logistics and EA management

PDAs with GPS


GIS for logistics and EA management

GIS packages offer network analysis features that:

Allow for immediate access to digital maps and other geographic information

Allow the planning staff to determine the distances, costs of travel, and other features

Allow supervisors to monitor the progress of enumerators as they move data from local and regional offices

Allow the centralization of information exchange between different geographies


PDAs/Hanheld with GPS

A wide range of options exist with GUI/OS flexibility

Allows for the collection of census data and geographic data simultaneously

Can provide supervisors locations of enumerators

Collect and send GPS coordinates to the GIS remotely for real-time data collection


END

use of geographic databases (maps) and other geospatial tools

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