If projected coordinate reference system (CRS) has yet been assigned to the project, then assigning a base map layer (i.e., Hybrid Map Bing, etc.) will automatically assign the Google Mercator coordinate reference system to the project. The Google Mercator CRS allows any location on the globe to be represented as X-Y coordinates.
Advantages of the Google Mercator CRS
- The entire spherical globe can be represented by one map.
Disadvantages of the Google Mercator CRS
- Regions near the earth’s north and south poles are greatly exaggerated. For locations further away from the equator, the amount of X-Y exaggeration increases the further away from the equator the location exists. Therefore, in more northern and southern locations, it would be advisable to switch to a regional (i.e., state plane, etc.) coordinate reference system.
- Only Europe and parts of Asia and Africa lie within the 1st quadrant of the Google Mercator CRS. Therefore, areas outside of the 1st quadrant will have negative coordinates. For example, North America lies within the 2nd quadrant and will have negative X coordinates. Therefore, it would be advisable to switch to a regional (i.e., state plane, etc.) coordinate reference system.