An approach is provided for filtering device location points in a sampled trajectory while maintaining path reconstructability. The approach involves determining a first location point in the sampled trajectory that is an unfiltered location point. The sampled trajectory includes device location points sampled by a device traversing a road network. The approach also involves determining a fastest alternative path from the first location point to a second location point. The approach further involves calculating a sampling time difference between a time at which the first location point was sampled and another time at which the second location point was sampled. The approach further involves designating the second location point as a next unfiltered location point when the sampling time difference is within a threshold value of a free-flow travel time calculated for the fastest alternative path. Otherwise, the second location point is designated as a filtered location point.