Processing of data from laser scan surveys for the creation of high-resolution height models of urban areas is the theme of the this research project.

The Claudiusstieg street in Hamburg's Marienthal quarter (Wandsbek area) has been identified by the city's department resposible for the drainage system as a small-scale area with particular drainage problems in heavy rainfall events. In this area, surface water that cannot be fed via gullies into the sewage system as well as backwater coming from overloaded main conduits accumulates at low points of the streets and flows into front gardens. Water has entered repeatedly in the past into houses and basements of nearby buildings.

Hamburg's Claudiusstieg has been chosen as a genuine example of many similarly affected areas to develop and implement innovative measures for small-scale flood protection in the framework of the EU-funded project Urban Water Cycle. Possible measures consist in feeding the water of an overloaded conduit to basins integrated in streets, protecting buildings and constructions, optimising the run of streets, etc. All these measure require good knowledge of the area's topography. The precision necessary for answering specific questions and for dimensioning using urban digital terrain model is in the area of a few centimeters. Furthermore, the models have to incorporate sharp edges (e.g. the edges of pavements) without blurring of smoothing them.

The results of this project shall allow to assess whether the cheap and easily collect data from laser scan airborne surveys, in contrast to the highly precise but expensive ground surveys, can be used to generate topography models of the necessary accuracy and resolution. With the future prospect of applying the method to large-scale areas in mind, it will estimated how much work is required for model generation and model analysis.

Urban flood area

Example of data points from laser scan airborne survey

Topography models before and after smoothing with edge preservation