An iso-line on a contour plot represents a constant value of a contoured variable. Whenever you are viewing a contour plot, the boundaries between contour intervals on the plot, represent iso-lines of the contoured variable.
The Add Iso-Line option allows the user to add user-defined iso-lines to a contour plot, representing any desired value of the contoured variable. To add an iso-line:
Select Add Iso-Line from the toolbar or the Lines sub-menu in the Groundwater menu.
As you move the mouse cursor over a contour plot, the exact value of the contoured variable, corresponding to the current cursor location, will be displayed as a popup "data tip". This allows the user to easily determine the value of the contoured variable at different locations, without having to refer to the legend.
When a desired value of the variable appears in the popup "data tip", or when the cursor is at a desired location, click the left mouse button, and the Add Iso-Line dialog will appear. In this dialog:
You may edit the Value of the iso-line.
You may choose Visibility = Always, if you want the iso-line to be displayed on all contour plots, or you may choose Visibility = the currently contoured data type, so that the iso-line ONLY appears when you are viewing contours of that data type.
You may select a Colour for the iso-line.
When you are finished with your selections in the dialog, select the Add button to add the iso-line to the contour plot.
You may add any number of iso-lines to contour plots, by repeating steps 1 to 4.
Iso-lines added with the Add Iso-Line option, are independent of the Contour Options, and are not affected by any changes which may be made to the Contour Options.
Choosing Visibility = Always for an Iso-Line, can be useful for comparing contours of different data types on the same view. For example, you might add iso-lines of Pressure Head to a view, and then change the data type to Total Head, to view Total Head contours and Pressure Head iso-lines.
To delete an iso-line, use the Delete Iso-Line option.