Assessing urban tree condition using airborne light detection and ranging

Accuracy of determining specific parameters of the urban forest using remote sensing

“…ALS data have predominantly been used for the detection of individual trees, and have been processed using the following algorithms: the tree climbing algorithm (Zhang & Qiu 2012), individual tree detection (ITD -Holopainen et al 2013), and watershed segmentation (crown-level fusion of hyperspectral imagery and ALS data - Alonzo et al 2014). Individual tree crowns have been delineated using canopy height models , image segmentation (Phu La et al 2015), local maxima algorithms (LMA), and the Koukoulas and Blackburn algorithm (KBA -Rahman & Rashed 2015), as well as a variable window filter (Plowright et al 2016). The accuracy of detection ranged from 69% (KBA method) to 99% (variable window filter method).…”

“…Apart from the method used, the character of the research area also impacted on the reliability of results, which varied with, among other factors, dominant species type (deciduous/coniferous), tree age, and quality of reference data (Sterenczak 2013). Plowright et al (2016), who achieved the most accurate detection results, used the variable window filter algorithm in their research, which, prior to that study, had mainly been applied to forest areas (Popescu et al 2003, Sterenczak 2013, where the parameters of the tool were calibrated in accordance with species composition and age/height of the forest. In Plowright et al (2016) research, the method was calibrated against a single species, but also indicated that it is possible to develop equations for other tree species and apply them in parallel.…”

Mapping tree canopies in urban environments using airborne laser scanning (ALS): a Vancouver case study

“…Optical sensor-derived data, such as aerial photography and Landsat satellite imagery, however, are generally poor when characterizing the vertical structure of urban vegetation (Plowright et al 2016). The dimensions and vertical architecture of trees reflect their productivity, age, overall health and vigor (Schomaker et al 2007).…”

“…The dimensions and vertical architecture of trees reflect their productivity, age, overall health and vigor (Schomaker et al 2007). A large, dense crown is an indicator of optimal tree growth, while less dense crowns can be indicative of poor health and stress (Zarnoch et al 2004;Plowright et al 2016). Although some vertical tree metrics can be estimated through indirect relationships with optical bands (Cohen and Spies 1992), additional three-dimensional data on tree condition is critically important.…”

“…An ALS instrument emits pulses of light that are reflected off trees, ground surfaces, and other terrestrial features and can penetrate through gaps in the foliage, enabling ALS to directly measure the vertical aspects of tree crowns and forest canopies (Plowright et al 2016;Coops et al 2007). A key benefit of ALS is the capacity to reliably obtain high-precision, three-dimensional measurements of buildings and trees over broad spatial scales which, as a result, has attracted significant interest among urban and natural resource managers (Hudak et al 2009;Williams et al 2018).…”