How to Create Maps Like These
Equal-Area-Maps.com has been produced as a demonstration for a series of articles concerning the correct use of map projections for online mapping, that was published at GeoWebGuru.com. The final two articles in the series were tutorials that showed you how to create interactive web maps that used equal area projections:
- How to Create an Online Map with a Non-Mercator Projection: Part 1 - a tutorial to using these projections with UMN MapServer
- How to Create an Online Map with a Non-Mercator Projection: Part 2 - completes the tutorial by implementing equal area projections in OpenLayers
The earlier articles in the series started with an introduction to map projections, geoids, and coordinate systems. This was followed by an article making the case against the Mercator projection for geostatistical applications, and arguing for an equal area projection instead. The remaining articles performed a survey of suitable global equal area map projections. The articles in the series were:
- Map Projections and Coordinate Systems: Part 1 - an overview of map projections
- Map Projections and Coordinate Systems: Part 2 - an overview of coordinate systems and geoids
- Choosing a Map Projection: Part 1 - argues against the Mercator projection for geostatistical applications
- Choosing a Map Project Part 2: Pseudo-conic, Azimuthal, and Cylindrical Projections - looks at some equal area alternatives
- Choosing a Map Project Part 3: Pseudo-cylindrical Projections - completes the survey of equal area projections
Brief Description
The site is based around a number of open source applications and libraries:
The basemap data was prepared using the ShapeLib tools, and MapShaper.org.
The base map is rendered by UMN MapServer and served as WMS tiles. Each individual map projection is created with its own MapScript file. All of these files are identical except for the projection references and the map extents - this is where a scripted or templated MapScript file could be useful.
The client maps are controlled using OpenLayers. OpenLayers has been expanded with the standard ScaleBar add-in, and the Proj4JS JavaScript projection library. Proj4JS is used by OpenLayers to transform the GeoRSS and KML data feeds to the chosen coordinate system. The "CEA" (Cylindrical Equal Area) projection type (used by the Behrmann projection) was written from scratch, and has been included in the latest Proj4JS build.
Links to the data sources used, are detailed on the Acknowledgments page.