Exploring Map Projections

Caitlin Dempsey


Created using D3, Map Projection Transitions provides an excellent way to visualize a wide range of map projections.  The page was created by Jason Davies, a freelance data visualization consultant.

Map projection visualizations offers the user a glimpse at what forty-one different projections look like.  Users can select one of the map projections from the drop down list or simply sit back and watch the map projections change every five seconds.  The pages notes, “By default, d3.geo will cut lines and polygons where they cross the antimeridian. This is usually appropriate for conic and cylindrical projections.

Users can change the view of the projection by using the cursor to drag and spin the map view.  This ability to interact with the map view extends the capability beyond the original creation of  Projection Transitions by Mike Bostock.

Davies has been collaborating with collaborating with Mike Bostock on some new map projections for D3.  Bostock is one of the original developers of D3 (see Making Maps with D3).

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Collignon map projection

Davies has a gallery of other map projects exploring projections.  The polyconic projection page lets you experiment with slicing the globe between four and 36 slices.  Each strip is projected using the equidistant conic projection for each standard parallel.

Polyconic projection.
Polyconic projection.

Other projection pages include a selection of “interrupted” map projections aside from the polyconic projection include Bartholomew’s Regional Projection and Spilhaus Maps.  Davies also explores butterfly maps such as the Gnomonic Butterfly Map.    I particularly liked Davies’ rendering of the Hammer Retroazimuthal Projection, which almost mimics a smiley face.  Numerous other map projection visualizations are available from Davies’ map page.

On a non map projection note, also check out Davies’ Countries by Area page, which organizes the boundaries of countries ranked in descending order by land area.  The land area GIS data is from Natural Earth, and the land area sizes are pulled from World Bank and CIA World Factbook.


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About the author
Caitlin Dempsey
Caitlin Dempsey is the editor of Geography Realm and holds a master's degree in Geography from UCLA as well as a Master of Library and Information Science (MLIS) from SJSU.