Understanding Map Projections
What are map projections and why should you care? Projection is a method of representing a spherical body (such as the Earth) on a two-dimensional surface (such as a computer screen). There are many different projections available, each of which represents the spherical curves of Earth in different ways.
Because every projection distorts the data in some areas to a certain degree, choosing the right projection for the maps you want to view is important. For example, if you will be creating maps of a very specific local region of the United States, you might want to use a State Plane projection which focuses on that region. This will minimize distortion of the region you’re working in at the expense of distorting other areas of the world. Because you will not need to display those other areas of the world, the distortion there is acceptable. For more information about the concept of projecting map data, we recommend this Wikipedia article.
Map Suite supports just about any projection imaginable because it uses PROJ.4 as its projection library. Some great resource for researching and finding what projection to use is spatialreference.org or visit wiki article for an overview of the most significant map projections.
Some of the more common projections include:
Geographic (Latitude/Longitude) – also known as WGS84 or EPSG:4326, this projection is commonly used by GPS satellite navigation and by NATO for geodetic surveying.
Google Maps / Bing Maps / OpenStreetMap – also known as Spherical Mercator or Web Mercator, this is the projection used by most online web map services. You will most likely need to use this projection if you want to overlay your layer data on top of a base map from one of the aforementioned providers.
State Plane – a set of 124 geographic zones designed for specific local regions of the United States. More information here.
UTM – a set of 60 geographic zones covering the entire Earth, each of which consists of a six-degree band of longitude. More information here.
If you are a programmer check out some of the Map Suite WebAPI projection online sample. You can also try out the Map Suite GIS Editor that allows you to reproject your data to almost any projection of your choosing.
