Index (Major) Contours

Index contours are lines of different colors, styles, or widths that appear at a regular frequency. With simple and logarithmic contour levels, this is called Major Contours. You can create index contours in several ways: use Major Contours with the simple contour levels. With advanced contour levels, you can set individual contour line properties, or use the Affected Levels group in the Line dialog to automatically assign the index contours.

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This is an example of a map with red index contours.

To set index line properties with simple contour levels, you need to set a major and minor contour level:

Click on an existing contour map to select it.
In the Properties window, click on the Levels tab.
Change the Level method to Simple.
Change the Major contour every value to the desired frequency for major contour lines. This is the interval for the index contours. To have a red index line every fifth line, set this value to 5.
Open the Line Properties section under Major Contours. This is the index contour properties. Set the Color to Red.
Open the Line Properties section under Minor Contours. This will set the line properties for all non-major contour lines. Set the Color to Blue.

To set index line properties with logarithmic contour levels, you need to set the number of minor levels per decade:

Click on an existing contour map to select it.
In the Properties window, click on the Levels tab.
Change the Level method to Logarithmic.
Change the Minor levels per decade value to the desired frequency for minor contour lines.
Open the Line Properties section under Major Contours. This is the index contour properties. Set the Color to Red. When using the logarithmic contour level method, the decades are automatically defined to be multiples of 10 (0.001, 0.01, 0.1, 1, 10, 100, 1000, etc).
Open the Line Properties section under Minor Contours. This will set the line properties for all non-major contour lines. Set the Color to Blue.

To create index contours with advanced contour levels, you can use the affected levels options:

Click on an existing contour map to select it.
In the Properties window, click on the Levels tab.
Change the Level method to Advanced.
Click the Edit Levels button next to Contour levels to open the advanced Levels for Map dialog.
Click the Line button to display the Line dialog.
Click the line Color button and change the color to red.
Set the index contour line properties in the Affected Levels group in the Line dialog.
In the Affected Levels group, set First to one, Set to one, and Skip to four. This means, starting with the first contour level, set one contour level to red, skip four contour levels, and then set the fifth contour level to red, skip four more levels, etc.
Click OK.
Next, set the line style and color used on the intermediate levels. Click the Line button on the Levels page.
Click the line Color button and change the line color to blue.
In the Affected Levels group, set First to two, Set to four, and Skip to one. This means, starting with the second contour level (the first level is a red index contour) change the line color to blue for the next four contour levels, skip one contour level, set the next four contour levels to blue, etc.
Click OK in the Line dialog to return to the contour map properties dialog. The first contour level line appears as red, the next four are blue, followed by one red line, etc.
Click OK in the contour map properties dialog to draw the map with the specified contour lines.

The Affected Levels group contains First, Set, and Skip fields. This group allows you to apply the selected line properties to a repeating series of levels. For example, use the Affected Levels options to create four blue contour lines, one red contour line, followed by four blue contour lines, etc. The Affected Levels group exists in the Line, Fill, Labels, and Hachures dialogs.

Index (Major) Contours

See Also