Method of milling asphalt

1. A method of milling asphalt with an asphalt milling machine, the asphalt milling machine having a milling machine body and a rotatable milling drum mounted on a lower portion of the milling machine body, the rotatable milling drum having a bottom surface, the method comprising:

sensing a relative elevation of an unmilled asphalt pavement surface adjacent to an area to be milled with respect to the milling machine body and rotatable milling drum;

determining an elevation of the bottom surface of the rotatable milling drum using a computer processor; and

based on a map, stored in a computer memory, of a design surface specifying a design elevation of a milled surface over the area to be milled, automatically adjusting the elevation of the milling machine body and the rotatable milling drum such that the rotatable milling drum mills the unmilled asphalt surface to the design elevation over the area to be milled.

2. The method of milling asphalt with an asphalt milling machine according to claim 1 , in which determining the elevation of the bottom surface of the rotatable milling drum includes determining the elevation of the unmilled pavement surface adjacent to the area to be milled by reference to results of a survey of the unmilled asphalt pavement surface adjacent to the area to be milled, the survey stored in the computer memory.

3. The method of milling asphalt with an asphalt milling machine according to claim 2 , in which automatically adjusting the elevation of the milling machine body and the rotatable milling drum includes comparing the elevation of the bottom surface of the rotatable milling drum and the elevation of the design surface to yield a correction value.

4. The method of milling asphalt with an asphalt milling machine according to claim 3 , in which the milling machine body and the milling drum are raised and lowered in dependence upon the correction value.

5. The method of milling asphalt with an asphalt milling machine according to claim 1 , in which determining the elevation of the bottom surface of the rotatable milling drum is accomplished by:

determining the elevation of the unmilled pavement surface adjacent to the area to be milled by reference to results of a survey of the unmilled asphalt pavement surface adjacent to the area to be milled, the survey stored in the computer memory; and

determining the elevation of the bottom surface of the rotatable milling drum by combining a relative position of the bottom surface of the milling drum and the elevation of the unmilled pavement surface adjacent to the area to be milled.

6. The method of milling asphalt with an asphalt milling machine according to claim 1 , in which an unmilled elevation of the asphalt pavement surface adjacent to the area to be milled is determined by:

sensing a relative position of the surface with respect to the asphalt milling machine using a side plate; and

referring to a survey of the unmilled asphalt pavement surface adjacent to the area to be milled, the survey stored in the computer memory.

7. A method of milling asphalt at a design elevation with an asphalt milling machine, the asphalt milling machine having a milling machine body and a rotatable milling drum mounted on a lower portion of the milling machine body, the rotatable milling drum having a bottom surface, the method comprising:

sensing a relative elevation of an unmilled asphalt pavement surface adjacent to an area to be milled with respect to the milling machine body and rotatable milling drum;

determining an elevation of the bottom surface of the rotatable milling drum by determining X and Y coordinates of the unmilled pavement surface adjacent to the area to be milled;

referring to a survey of the unmilled asphalt pavement surface adjacent to the area to be milled, the survey stored in a computer memory, to determine the elevation of the unmilled pavement surface adjacent the area to be milled;

combining the elevation of the unmilled pavement surface stored in the computer memory with the sensed relative elevation of the unmilled pavement surface; and

based on a map, stored in the computer memory, of a design surface specifying a design elevation of a milled surface over the area to be milled, automatically adjusting the elevation of the milling machine body and the rotatable milling drum such that the rotatable milling drum mills the asphalt surface to the design elevation over the area to be milled.

8. The method of milling asphalt at a design elevation with an asphalt milling machine according to claim 7 , in which automatically adjusting comprises comparing the elevation of the bottom surface of the rotatable milling drum and the elevation of the design surface to yield a correction value.

9. The method of milling asphalt at a design elevation with an asphalt milling machine according to claim 8 , in which the milling machine body and the rotatable milling drum are raised and lowered in dependence upon the correction value.

10. The method of milling asphalt at a design elevation with an asphalt milling machine according to claim 7 , in which determining the elevation of the bottom surface of the rotatable milling drum is accomplished by:

determining the elevation of the unmilled pavement surface adjacent to the area to be milled by reference to results of the survey stored in memory; and

determining the elevation of the bottom surface of the rotatable milling drum by combining a relative position of the bottom surface of the rotatable milling drum and the elevation of the unmilled pavement surface adjacent to the area to be milled.

11. The method of milling asphalt at a design elevation with an asphalt milling machine according to claim 7 , in which an unmilled elevation of the asphalt pavement surface adjacent to the area to be milled is determined by sensing a relative position of the surface with respect to the asphalt milling machine using a side plate, and then referring to the survey stored in the computer memory.

12. The method of milling asphalt at a design elevation with an asphalt milling machine according to claim 7 , in which an unmilled elevation of the asphalt pavement surface adjacent to the area to be milled is determined by sensing a relative position of the surface with respect to the asphalt milling machine using a sonic transducer, and then referring to the survey stored in the computer memory.