Data Aggregation might not make total sense to most, at least for casual users the mapping world. But it is one of the hidden items that really make a difference in what you ultimately get in your end products.
As per Merriam-Webster Aggregation is; “a group, body, or mass composed of many distinct parts or individuals” or “the collecting of units or parts into a mass or whole”
So how do you apply that to maps? Pretty easily actually. Maps are made up of many different layers or datasets that if compiled correctly you will never really see. Each one can contain different fields of data. They also cover various areas of the globe in the form of points, lines or polygons. Some maps we make that are server based and deployed to many users over vast geographies can contain hundreds of data layers. All covering different areas with various representations of the physical geography of the real world.
What does this have to do with the importance of aggregation?
Bringing that much (or little) data together can introduce quite a mess of complicated information. Therefore if designed properly for the end user sorting, grouping and scaling of this data results in easy to understand maps. Full of only the most useful information. So the way the data is aggregated is of most importance for a successful map delivery.