A method and apparatus for providing for real time automated control of the position of a blade on a earth-moving machine. The method includes providing a geography altering machine, including a blade and a computer, the computer having stored therein a reference line and a three dimensional computer model of a desired topography, providing a user defined offset relative to the reference line, determining a blade position in local coordinates, converting the local coordinates to reference line coordinates, utilizing the reference line coordinates and the user defined offset to calculate blade movement commands, and moving the blade in a direction required by the blade movement commands.