A method and apparatus for spreading ballast along railways makes use of an inertial measurement system to determine where to apply ballast from a hopper car. A variety of techniques can be used to determine the location and speed of the ballast spreading train, including manual or automated visual techniques, laser technology, radar technology, radio frequency transponders, magnetic sensor, thermal imaging and aerial photogrammetry. The invention also contemplates "on the fly" surveys and terrain profiling using lasers or radar.