Map Units and Distance Units in ArcView:
Map units are the units of the view’s display surface. If the view has not been projected, e.g. your data is in UTM or Stateplane, Map units are the physical units in which the coordinates of the spatial data are stored. If the view has been projected, e.g. Albers, Map units are the units into which this data is being projected in the view. ArcView uses the map units setting to determine the correct scale of your view. If Map Units are not set correctly, the scale ArcView displays for your view may be incorrect, and ArcView will not know how large to draw your view if you specify a scale for your view. Also, if the Map Units are not specified, the scale bar will not refelct a scale.
Distance units are the units used by ArcView to display or indicate:
1. The results of measurements you make on a view with the Measure tool,
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2. The dimensions of shapes you draw on a view with the Draw tool.
3. The dimensions of the selection box you define when selecting features in a particular area on a view with the Select Feature tool.
4. The distance tolerance specified in the Select By Theme dialog box for selecting one set of features from another.
5. The offset distance specified in the Geocode Addresses dialog box for placing the location of an address event.These measurements and dimensions are displayed on ArcView's status bar located at the bottom of the View. Each view has its own distance units setting, so you can choose the most appropriate units for the particular view you are working with. The default is unknown. This field is disabled until you select map units for your view.
