A scale bar as a layout element is always linked with the theme which is also placed on this layout. The scale bar serves for specifying the scale of map display when printing the layout.
To add a scale bar to the layout it is necessary to make the corresponding theme the only selected element. Then the button 
of the mode toolbar should be pushed and the scale bar should be placed on the layout page pressing the left mouse button in one corner of the rectangle and releasing the button in the opposite one. A dialog box “Adding/Properties of scale bar” shown at figure 47-5 will be opened.
Figure 47-5. Dialog box “Properties of scale bar”
If the user refuses to specify properties of the scale bar (for example, pushes the button Cancel) adding of the bar is canceled.
The created scale bar becomes selected layout element.
At figure 47-6 a layout page containing a theme and four scale bars of different types belonging to this theme are shown.
Figure 47-6. Layout page with a theme and scale bars
The upper scale bar located right below the theme will be displayed if the radio button Numerical is turned on in the property sheet of the scale bar, and in the pane Displayed units (see below) name of the unit “cm” is selected. As it is seen from the picture a scale bar of this type is not even a bar, but just numeric indication of scale of displaying a theme when printing a layout. The scale of displaying a layout on the screen is no way connected with the scale indicated by the scale bar.
If other displayed units (not centimeters) are selected, the scale of printing a theme will be displayed as it is shown at the next scale bar. After the text “1 cm” follows indication of the corresponding number of displayed units (in the present example – it is meters).
The word “Scale:” itself is not a part of the scale bar in both cases. It is a separate element of the layout inserted for explanation.
The second and third scale bars (radio buttons Scale and Split scale) look like rulers and differ only in the way the ruler is drawn (see the figure). In both cases the scale of the ruler is divided into two parts which are not equal: smaller points of the ruler are shown to the left from zero, to the right – bigger ones.
To evaluate the scale and display it correctly the system should know two things: firstly, what is the actual value of the “map unit” used for specifying feature coordinates on the map and, secondly, in what units the user wants to see the scale display.
It was pointed out above (chapter 9 “Map structure”) that when the user creates a map, he can select the coordinate system on the plane and a unit of measurement for this system in an arbitrary way. ObjectLand doesn't know what is the map unit actually equal to – one meter, 100 meters, a mile or some other unit. All coordinates of features are specified in map units, all lengths and perimeters are also displayed in these units. The only exception is scale bars in the layout for which the user can (and should) indicate the value of the map unit expressed in physical units of length.
The pane Map units contains two fields. The field Unit contains the name of the unit of length which was called “map unit” above. In fact, this field does not affect scale bar display at all, it serves as a commentary and it can be left unfilled. However, there is a convenient possibility to select one of the widespread metric or English units of length from the drop-down list: cm, m, inch, foot, etc. After the user makes a choice, next field Cm per unit is automatically filled in with the values of selected unit in centimeters (for example, 1 mile = 160970 cm). The user can change the value in this field manually, he can even specify a unit with a name “m” but which is equal, for example, to 200 cm. However, it shouldn't be done. Specifying centimeters manually can be justified only in the case when non-standard unit was selected initially when the map was created. For example, it is possible to enter the text “100 m” in the field Unit and number 10000 – in the field Cm per unit.
The pane Displayed units serves for determining the units of length in which numeric values on the scale bar will be displayed. This pane contains the same two fields as the pane Map units. The difference is that the name of the map unit entered or selected in the list will be displayed in the layout to the right of the scale bar (with the exception of the above described case when centimeters are selected as displayed units for the scale bar of numerical type).
The number and size of scale graduations are determined by fields of the pane Intervals. To specify graduations of the right part of the scale the user can select one of the two possibilities:
Specify the graduation size (in displayed units). To do this the radio button Calculate automatically to the left of the field Number should be checked and then the necessary size should be entered into the field Value. The biggest integer number of ruler points which will fit into the specified rectangle of the scale bar with the specified point size will be drawn (thus, the scale bar may happen to be a bit shorter than the specified rectangle).
Specify the number of points. For this purpose the radio button Calculate automatically to the left of the field Value should be checked and the required number of points should be entered in the field Number. The length of the scale bar will fully coincide to the specified rectangle, however, the size of the point can be fractional. To avoid display of long fractions it is possible to check the box Round values and specify the necessary accuracy of rounding values (in displayed units) in the field to:.
In the field Number of points the number of points of the ruler to the left of zero is indicated. The total value of all the left points is always equal to one point of the right part of the ruler.
One more button Style is left. When pushing it, a property sheet “Scale bar style” shown at figure 47-7 is opened.
Figure 47-7. Property sheet “Scale bar style”
The first three pages of this property sheet are standard. They allow the user to select fill and hatch style for the marks of the scale bar which are displayed by black color by default and also the line style which draws the bar and divides its points. Apart from selection of font and color of the text and setting parameters of height and indent (precisely as for the legend, see “Legends”) the page “Label” permits specifying orientation of inscriptions: Right, Up and Down. If the scale bar graduations are labeled by long numbers, it may be more convenient to place them vertically.
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