A zoom level in the GIS Editor is a concept that ties a particular scale to a preset level of map magnification. By default there are 25 separate zoom levels, and each time you zoom your map in or out, the map will snap to the closest one of these 25 zoom levels. The GIS Editor uses this concept of snappable zoom levels rather than a freeform system of zooming so that it is compatible with tiled web map services (otherwise known as base maps) like OpenStreetMap or Bing Maps, which have pregenerated map tiles at a series of predefined scales.

Lower zoom levels (i.e., 1, 2 or 3) represent scales where you are zoomed out to see the entire Earth. Higher zoom levels (i.e., 20, 21 or 22) represent scales where you are zoomed in very close to the ground. There are a variety of ways to zoom the map in or out and thus change your current zoom level; for details, see the article Navigating the Map.

The default set of 25 zoom levels can be customized to your exact needs by setting up a new map scale for each zoom level, and you can store different custom sets of zoom levels for use at any time. The remainder of this article describes that process.

To add, delete or modify the scale of a zoom level, you use the Manage Scales dialog. This dialog can be opened by clicking the Manage Scales button on the Home tab of the GIS Editor ribbon bar.

Current Scales - The set of zoom levels that the GIS Editor's maps are currently using is displayed in a list at the top of the dialog. Each zoom level is listed with its name (i.e., “Level 01”) and its corresponding scale (i.e., 591658710.9) and has two buttons next to it. The pencil button allows you to edit the scale associated with a zoom level. The delete button allows you to delete the zoom level.

The name of each zoom level is automatically generated and cannot be changed; zoom levels are named with a sequential number based on the scale of that level. Zoom levels are numbered from the highest scale (i.e., Level 01) to the lowest scale (i.e., Level 25). If you were to add a new zoom level with a scale that placed it somewhere in the middle, it would be named accordingly (for instance, Level 12) and the names of all the zoom levels that come after it would be incremented by one digit.

Add New - Click this button to add a new zoom level to the set. You will need to know the scale that you want to associate with your new zoom level.

Revert to Default Set - Click this button to restore the default 25 zoom levels that came with the GIS Editor. In the default set, zoom levels 1-20 match the 20 scales required by Bing Maps, OpenStreetMap and other commonly-used base maps and web map services.

This area lets you save and load custom zoom level sets.

Load Custom Set - Click this button to load a saved zoom level set. Loading a saved set will completely replace the current set of zoom levels with the ones stored in the custom set. You can also delete a saved zoom level set from here.

Save as Custom Set - Click this button to save the current zoom level set as a custom set which can be restored at any time. You will need to provide a name to identify your custom zoom level set. Saved zoom level sets are stored as an application setting of your local GIS Editor installation and can be accessed from any GIS Editor project on your computer.