Fusing GPS and Baro Altitude.

I am using the NEO_M8U UDR to acquire positional data for vehicle modeling purposes. One of the most important data input requirements is accurate road grade which is greatly influence vehicle power train load due the mean old gravity. Other UDR/ADR (Skytraq’s) includes a baro so I want to add the same functionality to the M8U UDR. Any suggestions would be helpful.

Thanks

Bruce Vernham