# Base Map

A base map provides geospatial context for the datasets that you work with. The base map that the Data Inspector Library uses is derived from the HERE Optimized Map for Visualization Plus (OMV Plus) catalog. And the data for OMV Plus is based on the HERE Map Content Data (HMC) catalog. This kinship ensures that the base map is always fresh (weekly updates), accurate, and compatible with other types of data stored on the HERE platform.

OMV Plus has been specifically adapted for performant web-based visualizations through simplifying geometries and filtering data. OMV Plus follows the Mapbox Vector Tiles (MVT) specification – an industry standard for map vector tiles.

## Base Map Sources

Depending on your region, you may need to use a different OMV Plus catalog as the base map source. Or you may want to use your custom OMV Plus catalogs for your specific needs.

The Data Inspector allows you to select among those base map sources to which you have access. For this, in the Data Inspector, go to the Control Panel, expand the Base map section, and choose the OMV Plus catalog you need. The Data Inspector remembers your last choice.

## Dependency Resolution between Base Map Sources and Visualized Data

The default base map for the Data Inspector is ruled by the dependencies of a layer to be visualized. For example, if your dataset is dependent on the HMC Japan catalog, then the OMV Plus for Japan is automatically selected and shown. If no matches are found, or if you have no access to OMV Plus Japan, then the default OMV Plus RoW (rest of the world) catalog is displayed. Also, if you select another base map with the Base Map Switcher, your choice is retained for the next sessions for the same catalog.

For more information on how to set layer dependencies, see the CLI Developer Guide.

You can disable this option in your custom visualizations by setting the enableBaseMapAutoSelection setting in the DataInspector configuration to false.