A spatial reference describes where features are located in the world. Most spatial references will be 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 will preserve certain aspects of the data (area, direction, shape, or distance) at the expense of the other aspects. Therefore, it is important to choose projections carefully based on what aspects of your map 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 (WGS 84) and 3857 - Web Mercator. WGS 84 is the geographic coordinate system used 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 will appear distorted on a Web Mercator map, especially near the polar regions.
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 chosen 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), WGS 84 will be chosen as the default spatial reference. If the dataset uses x- and y-coordinates (generally large positive or negative numbers representing meters and feet), no default spatial reference will be chosen. In this case, the spatial reference that the data uses will have to be selected from a list of available spatial references.
The basemaps included with Insights use the Web Mercator projection as their spatial reference. All datasets will be displayed in the spatial reference of the basemap, but the underlying data will not be changed or transformed. Therefore, 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 Create 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 your data does not use a spatial reference with a similar distortion, the analysis itself will remain accurate regardless of how it appears on the basemap.
Custom basemaps can also be created for your organization and can use a spatial reference of your choice. A custom basemap could be beneficial for your organization if you have a standard spatial reference that is used for the data in your organization or if your data is located in the polar regions.