Cached NGS_Topo_World_2D basemap C from ArcGIS Online fr Cached Esri_Imagery_World_2D basemap from ArcGIS Online Separating data into basemap and operational layers is the most important step in establishing a wellperforming Web mapping application. Basemaps provide a spatial context for an application by supplying general supporting information. Prebuilt basemap layers from ArcGIS Online are used in this example. Cached Esri_StreetMap_World_2D C basemap from ArcGIS Online ba Building basemaps and operational layers Basemaps provide a spatial context for an application by supplying general supporting information. Typically this information does not change frequently. With the exception of imagery basemaps (which may also be served dynamically using ArcGIS Image Services), basemap services are always cached. These maps are either developed in-house or accessed from public GIS servers such as ArcGIS Online. Imagery, a collection of hydrography layers, or a collection of street map layers are examples of basemap layers. Operational layers supply the specific data that is queried to perform both decisionmaking and task-based functions. Because the data supporting operational layers may change frequently, operational layers are often served dynamically. Customers and customer locations, sensor feeds, and work orders are examples of operational layers. Operational layers may also contain the results from analysis, features that require editing, or new data that needs to be made available to map application users. Separating data into basemap and operational layers is the most important step in establishing a well-performing Web mapping application. It allows the majority of the map layers that provide base data to be cached. Only a small percentage of the data will be served as dynamic, operational layers. Continued on page 46 www.esri www.esri.com ArcUser