A spatial reference describes where features are located in the world. Most spatial references are either geographic (using a geographic coordinate system) or projected (using a projected coordinate system). A geographic coordinate system uses a three-dimensional ellipsoidal model of the earth's surface to define locations using degrees of latitude and longitude. A projected coordinate system uses information from a geographic coordinate system and translates it to a flat surface. Each projection preserves certain aspects of the data (area, direction, shape, or distance) at the expense of the other aspects. It is important to choose projections carefully based on the aspects of a map that are most important. A projected coordinate system usually defines locations using x- and y-coordinates in feet or meters.
Each spatial reference includes a spatial reference identifier (SRID). The most commonly used spatial references in web mapping are 4326 - World Geodetic System 1984 (WGS84) and 3857 - Web Mercator. WGS84 is the geographic coordinate system used by the Global Positioning System (GPS), which makes it one of the most commonly used spatial references. Web Mercator is the standard projected coordinate system used in web mapping, in part because it displays direction accurately, making it useful for navigation. However, the size and shape of features appear distorted on a Web Mercator map, especially near the polar regions.
Enable location
Enabling location is a way to add spatial information to a dataset. One of the methods for enabling location uses coordinates (either latitude and longitude or x-coordinate and y-coordinate). A spatial reference must be specified to enable location with coordinates so that the coordinate information can be applied correctly to the data. If the dataset uses latitudes and longitudes (numbers between -90 and 90 or -180 and 180), WGS84 is used as the default spatial reference. If the dataset uses x- and y-coordinates (generally large positive or negative numbers representing meters or feet), no default spatial reference is specified. In this case, the spatial reference that the data uses is selected from a list of available spatial references.
Basemaps
The basemaps included with Insights use the Web Mercator projection as their spatial reference. All datasets are displayed in the spatial reference of the basemap, but the underlying data is not changed or transformed. All analysis will be completed in the spatial reference of the dataset, rather than the spatial reference of the basemap.
Some datasets, such as result datasets from Buffer/Drive Times or binned maps, may appear distorted on a Web Mercator basemap, depending on the latitude of the data. The Web Mercator projection distorts latitudes based on their distance from the equator. As long as the data does not use a spatial reference with a similar distortion, the analysis remains accurate regardless of how it appears on the basemap.
You can also create custom basemaps for your organization and can use a spatial reference of your choice. A custom basemap may be beneficial for your organization if you have a standard spatial reference that is used for the data in your organization or if the data is located in the polar regions.