Geographic Coordiante System are often identified by an EPSG Number. The two coordiante system most often used in web mapping applications are EPSG:4326 and EPSG:3857. But what’s the difference between the two!?
- EPSG:4326 (aka WGS84, unprojected) is a geographic, non-project coordinate system. It is the lat, longs GPS displays. Its units are decimal degrees. EPSG:4326 cannot be displayed in a meaningful way on a flat map.
- EPSG:3857 (aka Pseudo-Mercator, Spherical Mercator or Web Mercator) is a projected coordinate system. This is the coordinate system used by Google Maps and pretty much all other web mapping application.
Often, data is stored in EPSG:4326 and displayed in EPSG:3857 Also, a mapping API may take lat, longs (i.e. EPSG: 4326 ) as an input but when those coordinates are displayed on a map, they will be shown a map based on a Web Mercator (i.e. EPSG:3857) projection.
For a far better, more in-depth discussion of this topic have a look at EPSG 4326 vs EPSG 3857 (projections, datums, coordinate systems, and more!) by Lyzy Diamond.