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Creating Historical Digital Census Boundary Maps for Canada - a pilot project. Andrey Petrov , Laine Ruus, Data and GIS Services, University of Toronto Presented at CAPDU & IASSIST 2007 (r 3 ) May 16, 2007. Outline. Background The project The result. Background.
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Creating Historical Digital Census Boundary Maps for Canada - a pilot project Andrey Petrov, Laine Ruus, Data and GIS Services, University of Toronto Presented at CAPDU & IASSIST 2007 (r3) May 16, 2007
Outline • Background • The project • The result
Background • The basic building block of all larger census geographic areas in Canada has until recently (1996) been the enumeration area (EA) • EAs are defined as the geographic area canvassed by one census enumerator during the population census • EAs have not been geostatistically stable over time.
Bg contd • EAs are stackable, therefore can cover >100% of the land area • EAs are the smallest geographic area for which census statistics have been released since 1961 • The number of EAs changes from census to census
Bg contd • EA-level aggregate statistics have been produced and disseminated by Statistics Canada since 1961
Availability of census boundary files & reference maps • Reference maps (raster/print) at the EA-level are available for the following census: • 1971, 1981, 1986, 1991, 1996, 2001, 2006 • STC scanned to tiff: 1971-1996 (EAs and urban CTs) • Boundary files (vector files) at the EA-level are available for the following census: • 1981 (at STC, some lost), 1986, 1991, 1996, 2001, 2006 • Canadian Land Inventory EA boundaries from 1971 & 1976
summary of availability: Summary of descriptive and boundary data availability:
Bg contd • Demand for historical census data revitalized with release of each new census
bg contd • STC has previously done tests of: • Calgary – 1981 census • Kitchener-Waterloo – 1981 census • Québec – 1981 census
Our project • Create a historical digital census boundary files for province of Saskatchewan at EA level for 1976 & 1981 (projected to NAD83) • Why Saskatchewan? • simple geometry, only 2 CMA/CAs • modest census-to-census boundary changes • no changes to Representation Order (Federal electoral district boundaries)
Proj contd Objectives • Test alternative methods of re-creating historical EA boundary files • Assess problems and advantages of each method • Evaluate feasibility of extending the project to create a national coverage of historic census maps
Proj contd Resources used: • Canadian Land Inventory boundary files for 1976 (rural boundaries only) • STC digital boundary files of Regina & Saskatoon • Geography attribute files 1976 & 1981 • EA conversion file 1976-1981 • Area master file/road network files • Scanned raster/analog maps of EA boundaries for Regina, Saskatoon, and rest of Saskatchewan, 1976 & 1981
Proj contd Design requirements • Use only existing data available for the entire country • Develop a repeatable, time & resource efficient method • Miminize manual components • Provide GIS-ready digital output • Ensure compatibility with other STC datasets (1996 geographic base)
And the result • Vectorizing from raster maps proved not feasible • Project successfully produced EA boundary files for 1976 and 1981 for • Regina and Saskatoon CMAs • Remainder of the province: • 58 CSDs missing in 1976 • 78 CSDs missing in 1981
Inadequate and varying quality of scans Cluttered with secondary features (lines, labels, grid, etc.) Dashed lines All made successful automated vectorization extremely difficult
Resources required • Hardware: minimum 3.4 GHZ processor, 2GB RAM, 80 GV hard drive, 256 MB multi-port video card • Software: ArcGIS 9.x or higher, full package • Wetware: 155 hours, intermediate to advanced GIS skills (average 3.0 to 5.0 minutes per EA)
Where does the project go from here? • Whatever Paula Hurtubise said this morning………..
Project materials • Report: http://www.chass.utoronto.ca/~datalib/hurtubise/ReportStatcanr2_060331.doc • Zip file of all project files, including outputs: http://www.chass.utoronto.ca/~datalib/hurtubise/Saskatchewan_EA_projectr.zip