You can set a reference scale for your data frame, which fixes the size for symbols and text to draw at the desired height and width at the referenced map scale. This is like freezing the symbol and text sizes used in your data frame. One reason to set a reference scale is if you want the detail in your data frame to look the same on-screen as when you print it. It's useful to see the map's symbols on-screen at the size they will appear in the printed copy.
Let's say you are creating a map for publication that will be printed out at a scale of 1:25,000. If you set the data frame's reference scale to be 1:25,000, the symbols and text sizes in your data frame appear on-screen at the same size in relation to each other that they will have in your printed map. So you'll be able to zoom in on areas where there is a lot of detail and labeling and assess whether you want to adjust symbol sizes or the positioning of text.
When a reference scale is set, all feature symbology, labels, and graphics in the current data frame are scaled relative to the reference scale. However, you can disable scaling for individual layers: double-click the layer, click the Display tab, then uncheck Scale symbols when a reference scale is set. Since geodatabase annotation and dimension features have their own reference scales, they are not affected by a data frame reference scale.
Setting a reference scale causes your fill symbols to become larger as you zoom in from the reference scale and shrink as you zoom out. It's important to recognize this behavior because it is not typically what interactive map users want in their online, multiscale basemaps. When designing and working with interactive and web maps, it's likely that you will want to disable this reference scale behavior.
The two images below show the difference between having a reference scale set and not having it set when you zoom in and out on your map. In the top image, a reference scale is set, and in the bottom image, it isn't.
When no reference scale has been set (the default), symbol and text sizes remain the same on your data frame as you zoom in and out. So, for example, the width of the symbols used to show line features appears to be the same on-screen irrespective of what scale you are viewing your data frame at.
Setting a data frame reference scale
Here are the steps in setting a reference scale:
- Right-click the data frame in the table of contents and click Properties.
- Click the General tab.
- Type a value in the Reference Scale input box or choose a value from the drop-down list.
- Click OK.
- Alternatively, you can use the current map scale. Right-click the data frame in the table of contents, point to Reference Scale, then click Set Reference Scale.
From this same menu, you can also choose Clear Reference Scale or Zoom To Reference Scale to return to your printed map view from other map scales.