Duplicate labels are present for tiled or cached map services in ArcGIS Online

Description

When creating a tiled map service, the label properties in a map document are set to place one label per feature. However, there are multiple labels on a single feature after the tiled map service is published in ArcGIS Online.

In other instances, duplicate labels are present for map services created using the Maplex Label Engine in ArcMap. When map services are cached, duplicate labels appear in ArcGIS Online.

Cause

This is a known limitation with tile caches.

During a caching job, ArcGIS draws large areas to help reduce duplicate labels. These large areas, known as 'supertiles', are then divided into a smaller, individual tiles. Each tile is generated independent of the next tile. Duplicates can occur at the super-tile boundaries. This is because when a supertile is labeled, the label placement engine is not aware of labels on adjacent supertiles. The labeling engine may be making an effort to include as many labels as possible within a supertile, thereby placing some labels near the edge. It may do the same thing on the adjacent supertile, causing duplicates near the supertile boundaries. Therefore, there may be duplicates when viewing more than one supertile.

Duplicate labels are present in cache tiles if a dynamic labeling engine is used in a map document to place labels. However, these do not occur any more frequently than 4,096 pixels in any direction.

Solution or Workaround

Note:
An annotation is a special layer in which each label is treated as a feature with attributes. The attributes include an assigned place on the map for each label. An annotation layer can be edited to remove duplicate labels.

Note:
Map notes are not dynamically labeled and users must create each map note for each feature.