The answer can be found in our most recent paper “Updating Digital Elevation Models via Change Detection and Fusion of Human and Remote Sensor Data in Urban Environments” that has just been finally released in the International Journal of Digital Earth.
You can find a preprint version of the article freely accessible here: http://koenigstuhl.geog.uni-heidelberg.de/publications/2015/Hoefle/Klonner_et_al_2015_preprint.pdf
Klonner, C., Barron, C., Neis, P. & Höfle, B. (2015): Updating digital elevation models via change detection and fusion of human and remote sensor data in urban environments. International Journal of Digital Earth. Vol. 8 (2), pp. 153-171.