Use of geographic databases maps and other geospatial

Use of geographic databases (maps) and other geospatial tools during the census

Overview q Introduction: n From EA creation to EA map production for enumeration q Stages in quality control, EA map production and Database maintenance n n Introduction Quality control EA map production Database maintenance q Other geospatial tools n n GIS for logistics and EA management PDAs with GPS q Conclusion

Introduction q Accuracy and completeness of census data depend substantially on the quality of the cartographic base maps used by enumerators q A continuous process of quality control and quality improvement during data conversion allows review of all map products before distribution to enumerators. q This involves verification of the correctness of administrative boundaries by local administrators q 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 (component of quality assurance) q Quality control refers to a final check of the digital map database before the products are released for the census operation q 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 q Final quality assurance is best performed using printed hardcopy maps.

Verification q Match between geographic data and attributes n Correctness of the match between boundary data and attribute data o There should at least one map feature (a point, line, polygon) for each record in the geographic attribute table q Verification of several aspects of database integrity o Verification by census cartography staff will involve the inspection of the following acceptance criteria: n n Legibility sequence of data layers drawn on a map Map scale Source and copyright information

Quality Control (cont. ) q Verification by local authorities and final administrative unit check o These boundaries change often, with new states, provinces, and districts added on a regular basis irrespective of censustaking efforts o Ideally administrative boundaries are frozen by government decree several months before the census q Several options for dealing with this problem closer to the time of the enumeration include: n n n continuous tracking boundary changes are announced in advance determine a freeze date

Quality Control (cont. ) q 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. q 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; q 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) q Production of enumerator and supervisory maps n This can be done at the main NSO location or in regional field offices, depending on the type of NSO organizational structure q Develop enumerator/supervisory guidelines and training materials q Anyway, they should be simple, but contain enough information to allow easy orientation

EA Maps should contain the following information: q Entire enumeration area defined by a clearly indicated boundary line q Some parts of the neighboring areas and other geographic text and information to facilitate orientation q Features for EA maps should include: n n n q streets and roads buildings landmarks hydrological features other 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

Complete EA map with all components overlaid on one map display Main components are: Street network, Buildings EA boundaries layer Annotation, Symbols, Labels Building numbers Neatlines Legend

EA map production (including map printing) q Other Critical Factors n Barcoding o Many barcode readers now come with a USB interface with a decoder either integrated into the unit or separate o The NSO can use preprinted barcode labels or use software that creates a barcode for each map produced n Black and White o 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. n Design based on users experience, keep backup copies, automate printing

Database maintenance q 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 q This may require making the corresponding corrections in the digital census database, or it may require some additional field checking, or accessing satellite or aerial photo data to verify changes. q 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. q It should not, however, delay the release of census results.

Database maintenance: q Census mapping office should implement database maintenance procedures immediately following a census n q 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 n 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: q Staff continuity is critical n n 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 q Think long-term n The 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 q Support logistical planning and monitoring of census progress q Perform real-time or near real-time quality control of the census database q Common Geospatial Tools Used During the Census n GIS for logistics and EA management n PDAs with GPS

GIS for logistics and EA management q GIS packages offer network analysis features that: n Allow for immediate access to digital maps and other geographic information n Allow the planning staff to determine the distances, costs of travel, and other features n Allow supervisors to monitor the progress of enumerators as they move data from local and regional offices n Allow the centralization of information exchange between different geographies

PDAs/Hanheld with GPS q A wide range of options exist with GUI/OS flexibility q Allows for the collection of census data and geographic data simultaneously q Can provide supervisors locations of enumerators q Collect and send GPS coordinates to the GIS remotely for real-time data collection

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