18. The one or more computer-readable media of claim 16 , determining the predicted mode of transportation comprising determining probabilities for candidate modes of transportation for respective segments.
16. One or more computer-readable media having computer-executable instructions, which when executed perform actions, comprising: processing GPS data into walk segments and non-walk segments based on velocity data or acceleration data, or both velocity data and acceleration data; determining a length of respective segments; comparing the lengths of the segments against a merge threshold distance, and merging any segment having a length below the threshold distance into another segment; comparing the lengths of the segments against a certainty threshold distance; and for any uncertain segments that do not meet the certainty threshold distance, determining whether a number of consecutive uncertain segments is present, and if so, merging the consecutive uncertain segments into a non-walk segment; and determining a predicted mode of transportation for respective walk segments and for respective non-walk segments, based on features of respective segments.