The Epi Info™ Map module enables the user to plot the locations associated with study data on a global coordinate system overlaid with geophysical ("satellite") or geopolitical ("streets") maps. The street and satellite maps are, in essence, built-in Base Layers that supply geographic reference information onto which study data can be layered. User-defined Base Layers can be provided in the form of local shapefiles or remote data from KML/KMZ files or a map server on the Internet. Study data is applied in Data Layers, which can be divided into two groups. Both choropleth and dot density maps associate quantitative data with map regions, such as those defined in shapefiles or Keyhole data files. These map layers are useful for displaying large-scale public health information, where the number of cases, for example, is represented by color of, or dot density in, the jurisdictions drawn on the map. The other Data Layer group, consisting of case-cluster and spot maps, uses latitude and longitude to map the locations of subjects or other physical entities relevant to the study. The coordinates may be entered from GPS units in the field or translated from street addresses by the Check Code command GEOCODE. The user can also add markers, labels, and zones manually, by clicking on the map display.

Toolbar and User Interface

This section describes the Epi Map module window, the Toolbar, and the other controls that allow the user to interact with the module. When selected from the main menu, Epi Map opens a full-screen window, with a Mercator projection of a satellite map of the world consuming the majority of the display. There is a vertically oriented Toolbar, similar to that of the Visual Dashboard, consisting of a blue strip containing five icons in the opening window and expanding to as many as seven icons as data layers are added. These icons provide access to the major functions of the module, allowing the user to open and save map files; load base maps and data layers; and save maps as images, toggle the legend display, and create time-lapse maps using time-stamped subject data. On the map itself, at the upper left, are controls for zooming, scrolling, and changing orientation. At the upper right are buttons for switching between satellite and political/street maps, or no background map (blank). At the lower right are scale bars and an indicator for true North. At the bottom is the Map Layers tab; this will be discussed in the Base Maps and Data Layers section.

Map Layers

Geographic information associated with records collected using the Enter module is placed on the global coordinate system in Epi Map in layers, referred to as Data Layers. In contrast, reference information from map servers, shapefiles, or KML/KMZ files is associated with the map in Base Layers. There are two categories of Data Layers: Choropleth and Dot Density maps associate data records to regions or features by name and rely on geospatial data from external sources; Spot and case-cluster maps use latitude and longitude coordinates stored with each data record. The coordinates may be entered directly during data collection or determined from a street address or other geographical reference point using a GEOCODE command embedded in the Check Code of the data collection form. All Base and Data Layers are listed in the Map Layers tab along with their parameters. The tab enables the user to edit basic Data Layer parameters, move the layer forward and backward in this display stack, and access the layer's configuration panel.