Use case (author / website visitor): Marker grouping/clustering

[Malvoz]

This issue is for discussion of the use case “Marker grouping/clustering”, its examples & list of required capabilities.

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With the presumption that markers are in the tab order, clustering them can significantly lower the amount of tab stops required for a user to explore map content (related: WCAG 2.1 SC 2.4.1: Bypass Blocks). Additionally, marker clustering can help with reducing sensory overload.

See the article on marker clustering in regards to accessibility by @TechThomas:
https://equalentry.com/accessible-maps-on-the-web/#:~:text=Issue: Excessive Tab Stops

Related resources:

• Google Maps API: https://developers.google.com/maps/documentation/javascript/marker-clustering
• Leaflet JS API: https://github.com/Leaflet/Leaflet.markercluster
• MapBox GL JS API: https://docs.mapbox.com/mapbox-gl-js/example/cluster/
• MapKit JS API: https://developer.apple.com/documentation/mapkitjs/mapkit/annotations/about_annotation_clustering
• OpenLayers API: https://openlayers.org/en/latest/examples/cluster.html
• Bing Maps Control API: https://docs.microsoft.com/en-us/bingmaps/v8-web-control/map-control-concepts/clustering-module-examples/basic-clustering-example