LIDAR data provides valuable information about urban tree canopy management and can be used to analyze the dynamics of urban forests in a variety of different applications. A lidar instrument measures the distance to the ground by sending laser pulses in the air and collecting the light scattered back by the objects it hits such as trees, buildings, or landforms. Lidar instruments can measure not only the height of an object but also its width and volume.
As urban populations grow, so do urban tree canopy cover. It’s important to have accurate data about your trees—particularly around buildings, where they can cause expensive damage during storm events. This data can be gathered in various ways, including LIDAR (Light Detection And Ranging). But what is LIDAR? How does it help cities monitor their growing forests? Read on for a closer look at how you can use spatial analysis to monitor your city’s urban tree canopy management.
LIDAR (Light Detection and Ranging) is an active remote sensing method, where a sensor emits and captures short wavelengths of light to measure objects in high resolution. Urban areas are complex environments, and the ability of LiDAR to measure in three dimensions makes it more accurate in measuring the proportion and spatial distribution of tree canopies across these areas. LIDAR data sets are not limited to the tree canopy and vegetation of urban areas but can also provide high accuracy models for building footprints, digital terrain, and flood modelling.
Climate change awareness is on the rise and residents are demanding more ethical, sustainable community living, this method is important for cities because it can provide a spatial analysis of which areas of a city have greater or lesser tree canopy coverage. This can help to create more concentrated management of these areas so that every city resident has an equal opportunity to benefit from nature’s beauty as well as its environmental advantages.  The data gathered through lidar mapping also allows us to look at trends in specific regions over time, helping us track progress in urban tree canopy coverage over multiple years.
This can be used in conjunction with: Most large metropolitan areas have organizations dedicated to urban tree canopy management and monitoring. This information could be collected by either organization and then merged with spatial data gathered through lidar mapping methods.
In a joint venture with Newcastle city council in 2020, Anditi used LiDAR captured between 2008 and 2018 to map the growth and loss of forest cover across the Newcastle LGA.
New solutions were developed to approach technical issues such as misalignment between LIDAR years and between swaths from the same year. This was done by developing a correction matrix utilising various planar features in the data, and calculating the offsets between these planes in different swaths. With all of the data aligned, an area of comparison could be calculated. Another technical challenge was differing LIDAR density from 2-3 points per m² to 10 points per m². Low-density LiDAR can cause poorer edge detection and makes the comparison between datasets difficult. Correcting for this provided critical information on forest changes throughout the Newcastle LGA. Â
Change in forest cover was measured at 5m above ground and showed a range of outcomes. This included: Increase in tree growth, trees lost to development, new street plantings, and net tree gain. Understanding this change supports policy and planning into the future, and will ensure that heat island effects are mitigated, carbon storage is balanced, and quality of life is maintained and enhanced for residents and visitors.This data set can serve as a benchmark, and assist in the management of vegetation in the Newcastle LGA well into the future.
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