Contour When first displayed, the Contour window requests information on the contour interval and the initial (lowest value) contour line. The window will include the minimum and maximum values of the current overlay to help you select the appropriate contour interval and initial contour line. The algorithm is based on one described by Harbaugh (1990). Click on the Start button to start calculating the contour line. While calculating the contour, the pointer will change to an hourglass. If you feel that contouring is taking an inordinate amount of time, or that you made a mistake with setting the contour interval or initial contour line, the Stop button will do just that, stop the process. After completing the calculation, Graphic Groundwater will display the contour lines even if you have not checked the Contour box in the View Preferences window. If you would like to change the contour map, just enter new values for the contour interval and the initial contour line and click on the Start button. Clicking on the Finished button hides the Contour window.