Morakot hit Southern Taiwan on 8-9 August 2009. The tropical cyclone unleashed record rains of 2110 mm in 24 hours with highest record of accumulated rainfalls of more than 3000 mm in southern Taiwan, causing the worst flooding in a century. The area hit by the typhoon is around 10 thousand square kilometers. Landslides and flooding are the most important primary disasters. The authorities realized that the country was dreadfully lacking in detailed, accurate and current elevation data, as well as aerial imagery. In response, a national airborne LiDAR mapping program spanning 2010 to 2015 was launched with the aim of simultaneously capturing the territory (36,000km2) by airborne LiDAR and digital imagery. The results include very detailed digital elevation models (DEM) and digital surface models (DSM) of 1m grid and digital aerial photograph of 50 cm grid, as well as an inventory of the geological disastrous features with the acquired LiDAR data and images. In this paper, discussion will include the challenges of natural physiographical conditions and limited resources posed by this large-scale, long-term project and their resolutions with explicit guidelines, organization of task forces, automatic tools and full waveform capabilities.

In conclusion, the quality and accuracy of the resultant digital terrain models can be realized by (1) open-minded coordination of the 6 task forces, namely the client, the 4 survey teams, and the external QA team; (2) a well-prepared guidelines of airborne LiDAR survey; (3) new efficient tools should be implemented to facilitate automatic production and automatic quality check; and (4) a mass production software for processing full waveforms for detecting the weak echoes from the bare ground of dense forests to enhance a higher penetration rate and thus a better quality of DTM.