UAV Saltmarsh case study
In September 2009, we tested an inexpensive prototype consisting of a small remote controlled helicopter and a digital compact camera for saltmarsh mapping in southeast Tasmania. Tasmania’s saltmarshes provide important habitats for migratory birds and endangered shorebirds among other fauna. Future sea level rise and inappropriate management of saltmarshes in southeast Tasmania threaten these special habitats. Up-to-date and accurate spatial information and detailed environmental monitoring techniques are required to map the dynamics of Tasmania’s saltmarshes and to model impacts of future sea level rise. The figures below show the system and an example of an aerial photograph taken with the on-board camera. The results are very promising and we are working on a larger UAV system with multiple sensors. This larger helicopter will allow us to carry a laser scanner and camera setup simultaneously. Ultimately, given the system’s relatively low cost and logistical flexibility, it will allow us to frequently map and monitor saltmarsh ecosystems in great detail.
Saltmarsh at the southern end of Ralph's Bay, southeast Tasmania (with Mt. Wellington in the background), September 2009.
Remote controlled electric helicopter (Align Trex-500) with a custom-built camera mount and the Canon G10 compact digital camera (~15MP).
Darren Turner piloting the UAV up to an altitude of 70 m (covering 90 by 60 m in one photograph) with an average flying height between 30 and 40 m.
Example of an aerial photograph taken with the system described above. The image shows a range of different saltmarsh vegetation communities.
We also used a converted digital camera for near-infrared photography. This image shows the difference in NIR reflectance for the different saltmarsh communities for the area shown in the colour image above.
Georeferenced image based on witches hats on the ground with geodetic GPS coordinates. The witches hats are just visible as orange cones. Source: Xiaochuan Yang (Cassie).
Colour composite of three grey-level cooccurrence matrix (GLCM) texture measures derived from the image above. Source: Xiaochuan Yang (Cassie).
Object-based image analysis (OBIA) resulting in a detailed vegetation community classification based on the images above. Source: Xiaochuan Yang (Cassie).