The City of Canning required a vegetation cover and thermal imaging baseline study of the entire City using remote sensing techniques.
The project involved an aerial survey and classification of vegetation into prescribed height strata, and a detailed report analysing the proportion and quantity of representation of each class across a variety of zones. The thermal imaging called for the mapping of land surface temperature, identification and analysis of extremes across the city, and correlation with vegetation height strata.
Astron partnered with digital mapping leader AEROmetrex, who captured four-band aerial photography of the City of Canning in October 2015 at a spatial resolution of 15 cm with a Microsoft UltraCam Eagle camera. We used the resulting orthoimagery and point cloud to produce a digital surface model of the entire city with a 0.5 m resolution. Above-ground features were extracted from this, resulting in a canopy height model. This was classified into the prescribed height strata for analysis where we extracted and plotted zonal statistics for each of the specified spatial categories.
We then calculated land surface temperatures across the city from Landsat thermal imagery. We carried out detailed analysis on the relationship between temperature and canopy height, which showed a statistically significant correlation.
The graphical strata distribution plots demonstrated clearly the current status of vegetation height classes in the different parts of the City. It was shown that though temperature variation as a result of vegetation height differences were small, their relationship was distinct to a 95% confidence level. Bare, non-vegetated ground and building tops had the highest temperatures. Where vegetation was present, temperatures were observed to fall with an increase in vegetation height. This relationship held until vegetation reached a height of about 15 m, above which temperatures were seen to start to rise again.