Tag Archives: Minard
By Kenneth Field, Esri Research Cartographer
The default projection for all basemaps in ArcGIS Online is Web Mercator. In a previous blog entry, Bern Szukalski explained using custom basemaps as an alternative to Web Mercator and the ArcGIS Resource Center provides information on how to build online basemaps. Mercator projections are very useful for certain mapping tasks but not so good for others because they dramatically exaggerate northern and southern latitudes. This exaggeration deforms the shape and size of areas. Whilst Web Mercator has become a widely adopted web mapping standard (because of the tiling system being well suited to this spatial reference), there are situations where you may want a different map projection. In thematic mapping, for instance, you might want to preserve areas or shapes or even use a more pleasing view of the world than Web Mercator provides at small scales. This blog entry describes how you can switch out the default basemap for your own, simplified thematic basemap.