A marker, sometimes also called a map pin, identifies a location in the map. This location can be a place, point of interest, or any other object.
Adding markers is one of the most important and powerful functions of a map because it helps pinpoint the location and establish a connection to reveal additional content. Markers are strong focus points with a high capability of being interacted with. They typically trigger MapTips, info pop-ups, or info panels.
Markers are used to highlight a special location on the map, usually after input by the user such as clicking a search result, using the location finder, or selecting a point feature. In this sense, markers are different from point symbols because they indicate points that were selected by the user or stand out through their importance to the subject, as shown in a store locator, for instance.
Route positioning uses markers to indicate the start and end points of the route. The location list uses markers to establish a unique relationship between the item in the list and the point on the map. Locator apps such as hotel booking sites, store locators, or site finders may choose to display points using markers instead of simple point symbols.
Markers differ in color, shape, and size but are typically graphics. As a convention, the upside-down, teardrop-shaped marker indicates an exact location selected by the user. This user input could be clicking a feature, performing a search, using the location finder, or selecting a way point of a route. Alternative marker symbols can take any form or shape, such as pushpins, circles, or rectangles, and may include numbers or letters to reference content displayed in a list.
Markers must be interactive and support click or tap and optionally hover or drag interactions in the following ways:
- Click or tap should open an info pop-up with additional information about the location, such as title, description, photos, reviews, or action buttons.
- Hover opens a MapTip displaying short and informative information about the marker.
- Drag is used to adjust the location. On mobile devices, the marker may be placed in a fixed center position of the map, allowing users to drag the map underneath instead of dragging the marker itself.
The decision whether to use markers or regular point symbols should be based on the following:
- Density: Marker. Data with few overlapping points lends itself better to using markers.
- Information retrieval: Marker. Necessity to reveal more detailed information may indicate the need for markers.
- Subject matter: Points. Indicating physical locations works better with points.
- Classification: Points. Points that don’t need to be symbolized based on an attribute value are preferred but might still work if classification is Boolean, such as on/off, available/not available, or found/not found.
After a marker is placed, the map zooms to and centers on it; adding a tiny bounce animation is nice, too. The exact zoom level depends on the purpose of the app. A parcel viewer app may zoom to a large scale showing the prop-erty at that address almost entirely, whereas a store locator may zoom to a smaller scale that includes multiple stores close to that address.
The Commercial Real Estate Site Selection app allows users to compare multiple retail, office, industrial, or mixed-use sites side by side. The app uses ArcGIS GeoEnrichment Service to enhance existing data with additional location-based information such as demographics. When a user accesses the app, they see a list of sites and an interactive reference map with graduated symbols. Larger symbols indicate that more sites exist in this area. The items in the list have an icon button to add the site as a comparison card to the main content area. Each comparison card shows basic information, including the location and geoenriched data about the site, such as population, housing, income, and education. A unique feature of this app is how it uses a static map with a marker on top to communicate the site’s location. The boundary around the marker shows the area an average person can walk in 10 minutes, which is used as input for reporting the site statistics.