| see: http://bost.ocks.org/mike/map/ |
| |
| brew install gdal |
| npm install -g topojson |
| |
| To generate continental US map: |
| |
| $ wget 'http://www.naturalearthdata.com/download/50m/cultural/ne_50m_admin_1_states_provinces_lakes.zip' |
| $ unzip ne_50m_admin_1_states_provinces_lakes.zip |
| $ ogr2ogr -f GeoJSON -where "sr_adm0_a3 IN ('USA')" states.json ne_50m_admin_1_states_provinces_lakes.shp |
| |
| edit states.json to remove data for Hawaii and Alaska |
| |
| $ topojson states.json > topology.json |
| |
| |
| The .shp file above is incomplete (USA and part of Candada.) |
| So it may be that each region requires a bit of research to generate. |
| Ideally a source for public domain shp files can be found that covers all geographic regions. |
| |
| |
| For Canada: |
| |
| # wget 'http://www12.statcan.gc.ca/census-recensement/2011/geo/bound-limit/files-fichiers/gpr_000b11a_e.zip' |
| # unzip gpr_000b11a_e.zip |
| # ogr2ogr -f "GeoJSON" -s_srs EPSG:21781 -t_srs EPSG:4326 canada.json gpr_000b11a_e.shp |
| # topojson --id-property CFSAUID -p name=PRNAME -p name canada.json > topology.json |
| |
| |
| This produces a very large (5MB) file and draws very slowly in Chrome. |
| So some additional processing is required to simplify the geometry. (It is not checked in.) |
| |
| Also, the specification of object structure within the geojson is unclear. |
| In the US map the geojson structure is |
| |
| json.objects.states |
| |
| but in the Canadian data it's |
| |
| json.objects.canada |
| |
| |
| Lastly, the projection that is used may be tailored to the region. |
| The preferred projection for the US is "albers" and d3 provides a "albersUSA" which can be used to |
| project hawaii and alaska as well |
| |
| For Canada, apparantly a "Lambert" projection (called conicConformal in d3) is preferred |
| |
| see: |
| https://github.com/mbostock/d3/wiki/Geo-Projections |
| http://www.statcan.gc.ca/pub/92-195-x/2011001/other-autre/mapproj-projcarte/m-c-eng.htm |
| |
| |
| Summary: |
| - some additional work is required to fully generalize maps functionality. |
| - it may be worthwhile for ONF to provide the topo files for key regions since producing these |
| files is non-trivial |
| |
| |
| |
| |