Abstract
This paper compares three methods of estimating the present road grade based on global positioning system (GPS) measurements. The different methodsare rated based on their errors compared to a reference road grade profile. The first method extracts the vertical velocity from the 3D velocity reported by the GPS receiver. The second method relies on numerical differentiation of the altitude profile. Finally, the third method uses a Kalman filter with the two previously mentioned vertical velocities as inputs and included noise dynamics. It is found that the second method produces the best trade-off between accuracy and computational complexity for the intended application.