Layouts: Scale Bars

scale bar frames in layouts are frames that contain a scale bar shape.  They are created entirely within the layout and show a scale bar shape that can be picked in their Scale Bar dialog from a variety of scale bar shapes. The size of the scale bar will automatically be guided by guided by whatever is the topmost map frame below the scale bar frame in the Layers pane display stack.  


This topic discusses the use of scale bar frames in Layouts.  For info on adding a scale bar virtual layer to a map, see the Scale Bars topic.


To create a North arrow frame, open a layout, choose the Create Scale Bar tool from the drop-down menu for the cursor mode button in the main toolbar, and then click the approximate center of the scale bar frame you would like to create.   



A small scale bar frame appears at that location with the default scale bar in the frame.  The Info pane pops open to the Style tab so we can edit the scale bar and change colors, style, and size as desired.  When we would like to apply any changes, we press the Update Frame button.  We can resize and reposition the scale bar frame as desired, or click again to create another scale bar frame.   


 When we are finished creating scale bar frames we can choose the Default + cursor tool in the main toolbar to exit Create Scale Bar mode.  


Keyboard shortcut: Press Shift-Esc to get back to Default navigation mode.


We open the layout and click on the Create Scale Bar tool in the cursor mode button in the main toolbar.  



In the layout we click approximately where we would like the scale bar frame to appear.



A small scale bar frame of default size appears at the clicked spot, using the default scale bar style, a black and white bar.  The scale bar is sized correctly, taking its size from the topmost map frame that is below the scale bar frame in the Layers pane display stack.  In this case, the topmost map frame shows a map of Monaco.


In the Layout window, the scale bar frame is already enabled for editing, as if we had Alt-clicked an existing frame.    


In the Layers pane, a new Scale Bar frame appears as well:



The Info pane pops open with the default scale bar and styling for the scale bar frame as seen in the illustration at left below.




The Info pane launches with a light blue background by default in the preview pane for the grid.  The default light blue background makes it easy to see scale bars that use white or other light colors.   We can change the background color as desired by clicking the square color well box in the upper right corner of the preview pane.


We can change the style of the scale bar by clicking the [...] browse button, and then in the Scale Bar dialog choosing a different style.   See the Scale Bars topic for examples using the Scale Bar dialog.


If we like we can manually change the X and Y extents of the frame by clicking on the Position tab and then entering whatever extents in millimeters we desire. Except for special purposes, doing that is inefficient as it is easier to simply drag the borders of the frame to resize it and reposition it as we like.   Press the Update Frame button to apply the changes.



Immediately, the new scale bar style appears.  Now we will resize the scale bar frame.


To do that, we click on the Default cursor button in the main toolbar, to exit Create Scale Bar mode.  This allows us to click into the Layout without creating a new scale bar frame with each click.



We drag the corner handles to resize the scale bar frame as seen above.  



Back in the Info pane we click the [...] browse button to launch the Scale Bar dialog.



In the Scale Bar dialog, we adjust settings as shown above.  We have increased the Stroke width to 3 and we have changed the font to Segoe UI semibold.


Press OK.



Back in the Info pane, we press the Update Frame button to apply the changes.



The scale bar in the scale bar frame immediately changes to the new style properties specified.   We may have to expand the size of the frame by dragging handles to make it bigger, for the scale bar to fit as we have specified.


We can see how the scale bar will look by Alt-clicking outside the frame, to eliminate the edit handles.



  We click the Margins button to turn off margins, to see what the layout will look like when printed.




If we like, we can Alt-click the scale bar frame and then in the Info pane go into the Scale Bar dialog to change the style of the text bar used, and also using a smaller Stroke of 1 point.  The result is seen above.


The small size of the illustration does not allow the 1 point white halo used around the scale bar style to be rendered precisely.  



We can zoom into the layout to see that the scale bar and text caption will be rendered precisely accurately when the layout is printed.

Scale Bar Dialog

The Scale Bar dialog used for Layouts is slightly different from the dialog used for scale bar virtual layers in maps, for example, it does not have an Apply button.  In layouts, the position, margins and size of the scale bar frame are set by interactively positioning the frame and by dragging edit handles on the frame.  In maps, the position, margins, and size of the scale bar are set with additional controls in the Scale Bar dialog.  See the Scale Bars topic for the dialog used for virtual Scale Bar layers in maps.



The Scale Bar dialog allows setting the following parameters:


(Preview pane)

Shows a preview of the current settings used in the dialog.  The background color is light blue by default, to allow either very light or dark shapes to be visible.   Change the background color of the preview pane by clicking the square box in the upper right corner of the preview pane.

(Shapes gallery)

Choose a Scale bar shape from a gallery of popular shapes. Hovering the mouse over a shape will show the name of that shape in a tooltip.

Foreground and stroke color for shapes and text.

Fill color and the color for halos.

Buttons that show a small "box" sub-icon indicate that color has been changed from the default.


Stroke width for the shape


Check to show text caption with the number of units.

Font for text. Fully configurable for typeface, effects, bold, etc.

Font size for text.


Width of background color halo for shape and text.  Default: 1pt.   Setting Halo to 0 turns off the halo.


Uncheck the Auto box to manually specify the length of the scale bar in the unit of measure specified in the Unit box.  If the Auto box is checked (the default), or if the space allocated for the space bar in the Size parameter is too small to show the desired length, the length of the scale bar will be computed automatically based on the specified size, unit and the current scale. The width of the scale bar is slightly reduced so that the reported length is rounded to no more than two significant digits.


Unit of measure shown in the text caption.   Default: coordinate system unit for the map window, specified by choosing (auto).


How Scale is Calculated

Scale bar frames size and caption their scale bar based on the topmost map frame that is below the scale bar frame in the Layers pane display stack.  


If the scale bar frame in the Layers pane display stack is below all map frames in the layout, the scale bar frame will orient the scale bar it contains based on whatever is the topmost map frame in the Layers pane display stack for the layout. 


A common error in cartography is to think the scale bar should show different scales when moved to different locations in a map that has obviously varying scale at different locations.  But that is an error because such projections in fact have only a single scale throughout:  the evident variation in scale is a result of how those projections distort their contents in a way that is not true to scale.  What they show at different locations is distorted and does not match what you would expect to see given the scale used throughout the map.


We can see how that works using a layout that contains one component layer, a map that shows the countries of the world using Mollweide projection.  Mollweide projection only has true scale along two parallels of latitude, at approximately 40 degrees North and South, with huge distortion elsewhere.


The layout has a latitude / longitude Grid turned on for the world map component frame, with grid step set to 30 degrees, so we can see from the meridian lines the bearing to North at various locations in the map.



Positioning the scale bar frame by Africa near the Equator reports the length of the scale bar as 2500 kilometers.



Moving the scale bar frame to a position above Scandinavia reports the same length of the scale bar, even though the meridians of longitude are much more closely spaced in that position of the map.


What is going on is that Mollweide projection has the same scale everywhere, but, as the Mollweide projection topic reports, the scale is only true at approximately latitudes 40 North and South.  Position the scale bar at either of those latitudes, and the region covered by the scale bar on the actual planet indeed would be 2500 kilometers.  Everywhere else, because of the massive distortion caused by the projection, the distance covered would not be 2500 kilometers.


Like many things in cartography, using scale bars in layouts should be approached with common sense.  It does not make sense to use scale bars with some projections, like Mollweide, in displays that show regions where the distortion built into the projection makes the use of scale bars confusing and deceptive.   With many projections, it only makes sense to use scale bars when the region being displayed is that part of the projection where scale is true.   


For example, we can reasonably use scale bars when using Lambert Conformal Conic projection for views zoomed into the one or two chosen standard parallels where scale is true.   Scale also is true at the center of an Orthographic projection, so if we use an Orthographic projection centered on our area of interest we can use a scale bar confident that it will be accurate for displays zoomed into that area of interest.


See Also

Layers Pane


Info Pane


North Arrows


Scale Bars








Layouts: Create Commands


Layouts: Text Frames


Layouts: Legends


Layouts: North Arrows


Layouts: Grids


Layouts: Layers Pane


Layouts: Info Pane


Layouts: Alignment Commands


About Projections