 maps help you visualize and analyze data. Map visualizations are a highly efficient, eye-catching tool for geospatially analyzing data. For example, you may have seen maps like these to follow up on the COVID-19 pandemic, where the colors indicate the number of confirmed cases by country. How can we create geospatial visualizations like this in DJS2? This video will talk about the basic concepts of using maps for aggregate data in DJS2. You'll understand how data can be viewed in maps, the concept of map layers, and some specifics about the types of layers that can be used to create maps from the aggregate data model. We'll learn how multiple data types can be shown in a single map using layers. Let's start with the basics. Maps in DJS2 is the geographic information system, or GIS, that allows you to view data associated with GPS coordinates that relate to points or areas on a map. Maps can include multiple layers, which each represents specific data geographically. Each map starts with a base layer or base map. A base map is a layer with geographic information that serves as a background to any map we create in DJS2. There are several options of base maps from OpenStreetMap and Microsoft Bing Maps. Other layers can be added on top of the base map, where each layer represents a data item. These data items can be data that are specifically collected in the DJS2 instance, or pulled from external sources. Note that for DJS2 data, these point or area coordinates must be configured by a system administrator before you will be able to view the data in a map. You can learn about this in the DJS2 documentation. Each additional layer can show data, such as data items collected, site locations, area boundaries, climate data, or population, among others. Layers are stacked on top of each other and combined into a single visual analysis. Layers can also have their transparency adjusted, which determines the degree to which the layers blend into each other visually. Using these features, we can create maps to facilitate data analysis. Let's look at a specific example of a map in DJS2. One scenario where it can be helpful to view data in a map would be in monitoring an immunization program. Let's say we want to look at an indicator, such as dropout rates, for a specific vaccination series by district. Are the districts close to one another with a high vaccination dropout rate? What is happening in these areas? Using a map, we can formulate questions like these and identify areas for follow-up. The main types of layers used to analyze aggregate data in DJS2 are thematic, facilities, and boundaries. A thematic map depicts information about a topic or theme over a geographic area. These data themes can be shown using a choropleth or bubble map. Choropleth maps display the data based on geographical boundaries, such as district boundaries, as colored polygons. Bubble maps display coordinates of sites or areas with circles. The size of the circle depends on the value associated with that particular location. Locations with larger values have larger circles, while locations with smaller values have smaller circles. The facilities layer shows the location of health facilities with different icons or images to show different categories of facilities, such as health centers or dispensaries. And the boundaries layer displays the boundary lines between political and administrative entities, such as countries, regions, or districts. In summary, you can use DJS2 to create maps made with multiple layers to support analysis of data that is tied to GPS coordinates. The main layers used to view aggregate data in DJS2 maps are the thematic, facility, and boundary layers.