Urban Vegetation Management using LIDAR

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The Urban Environmental Crisis LIDAR and Urban Forest Management - Canopy Height Model - Canopy Coverage Map - Canopy Stratification Map - Canopy Coverage By Unit Area �I

- Canopy Change Detection

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LIDAR Beyond Urban Forest Management Benefits of Aerometrex LIDAR Mapping Urban Vegetation in South Australia

ities across the globe face many environmental challenges and governments at every level are placing great emphasis on developing sustainable urban areas. Increasing the community's resilience to the ongoing effects of climate change has become one of the most critical considerations for strategic planning within the governments.

'Urban forests' is a general term used to describe any trees within the urban environment. They have been identified as an extremely important asset that can mitigate numerous negative environmental effects and provide many economic & social benefits. Specifically, they can have positive effects on community health, well-being, and safety, improve local air quality, stormwater attenuation and combat the effects of climate change through carbon sequestration and reducing the magnitude of urban heat islands.

There have been increasing efforts by national and local governments to measure, assess and increase the number of trees and green spaces across urban areas. Developing methods that can be used to measure this natural asset accurately and repeatedly is a fundamental challenge for management experts - if assets are not accurately measured, they cannot be effectively managed.

Detailed and accurate assessments of the extent and spatial distribution of tree canopy cover has become a critical tool for policymakers to assess the effectiveness of ongoing environmental management practices and to achieve regional environmental targets.

LIDAR ANE>-----� URBAN FOREST MANAGEMENT LiDAR, which stands for Light Detection and Ranging, is an active remote sensing method that is used to accurately measure the landscape in three dimensions. When laser pulses emitted from a LiDAR sensor are incident on a tree, a portion of the energy is scattered or reflected back towards the sensor by the top of the tree canopy, and the remaining energy is transmitted through gaps in the foliage and interacts with lower branches, leaves or stems or even the ground surface below the tree. The unique way in which LIDAR pulses interact with vegetation make it possible to quantify vertically distributed forest and individual tree attributes and extend traditional 2-dimensional environmental models into the third dimension.

Urban environments are particularly challenging to classify and map using remote sensing techniques as they are geometrically, texturally, and spectrally complex. Compared to other remote sensing methods for mapping vegetation (e.g. statistical approximations, supervised classifications and Machine Learning/ Al based two-dimensional classifiers), LiDAR explicitly measures the location of trees in three dimensions and therefore has the potential to generate more accurate measurements of the proportion and spatial distribution of tree canopy coverage across urban landscapes. This survey technology, and the information derived from it, has become a critical asset for strategic environmental planning within local government n orga n isatio s. ...

Numerous targeted vegetation metrics can be derived from LiDAR that provide actional information to help maintain and increase the tree assets in urban areas. Metrics can be customised to suit the specific needs of clients on a project basis, including minimum height threshold of trees. In combination, these metrics provide an unparalleled snapshot of tree canopy coverage across an area of interest, providing experts with highly accurate three-dimensional tree canopy attributes.

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CANOPY

HEIGHT MODEL

A Canopy Height Model (CHM), also known as a Digital Canopy Model (DCM), describes the precise height above ground of the top of tree canopies across an area of interest. Canopy Height Models provide valuable information and clear visualisation of the height of trees throughout the urban landscape. It can be used to locate tall, significant trees, track the growth of trees as well as identify trees that could potentially interfere with infrastructure such as power lines, greatly reducing the time and effort required to identify and plan tree asset maintenance.

Canopy Height Model of a site in Canberra, showing the height of tree canopy above ground. The model has a cell size of 1 m x 1 m and describes trees that are above three metres in height. Areas of no data correspond to those that either have no trees or have trees that are below the threshold of three metres.

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CANOPY COVERAGE MAP

Tree Canopy Coverage Maps show the precise boundaries of the tree canopies within the area of interest. This makes it possible to extract the total area that is covered by tree canopy and allows for the precise percentage of tree canopy coverage of any given area of interest to be calculated, whether it be a suburb, council or metropolitan area. Tree Canopy Coverage datasets can also be combined with cadastral, land use or land ownership datasets to provide statistical breakdowns of the distribution of tree canopy across the community. Statistics such as these can be used to develop targeted management policies and help local government reach greening initiative targets.

Canopy Coverage Map of a site in Canberra, showing the horizontal extent and precise area of tree canopy. This is a vector data set showing the horizontal extent of tree canopy cover above three metres across the pilot area of interest. This data is derived from the canopy height model and depicts the exact area that is covered by tree canopy.

Tree Canopy

CANOPY STRATIFICATION MAP Canopy Stratification Maps show the distribution of tree canopy coverage across predefined height above ground intervals.

Canopy Stratification Maps provide valuable information about the vertical structure of the urban forest across an area of interest. Data such as this can help guide tree asset management by revealing the vertical distribution of tree canopy cover and quantifying the contribution of young versus established trees to the overall canopy coverage. This information can be crucial for the development of tailored environmental policies combining planting initiatives and established tree preservation.

Canopy Stratification Map of a site in Canberra showing the horizontal extent of tree canopy in defined height intervals.

This vector data set defines the area covered by tree canopy within height intervals, ranging three metres up to the max canopy height. These maps can be considered as multiple, stacked Canopy Coverage Maps, each of which corresponds to canopy within each height interval.

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CANOPY COVERAGE

BY UNIT AREA

Tree Canopy Coverage by Unit Area Maps provide an accurate, subjective snapshot of the spatial distribution of tree canopy cover across an area of interest. By combining this data with local government or suburb boundaries, management experts can gain a clear understanding of which areas within the community need to be targeted in order to increase tree canopy cover. These maps can be used to formulate tree planting initiatives which will deliver the greatest immediate benefit to the community in areas that are in most need of increased tree canopy coverage.

Canopy Coverage Map (by unit area) of a site in Canberra showing the precise proportion (%) of tree canopy cover (above three metres) in each 100m x 100m unit area. It provides a snapshot of the distribution of tree canopy cover above three meters in height which is free of biases that can be caused by depicting tree canopy coverage per council or suburb area.

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CANOPY CHANGE DETECTION The methods used to extract tree canopy attributes from LiDAR are accurate, cost-effective, and repeatable. Vegetation metrics can be easily and simply compared across repeat LiDAR captures to develop an understanding of the degree to which tree canopy is changing across the urban landscape. Observations such as these are critical to assess the effectiveness of tree canopy management and in adapting current strategies to the dynamic challenges that will be faced by communities in the coming years.

The change in tree canopy height can be measured over time to give an understanding of how trees are growing, as well as where trees are being removed. Building construction and demolition can be measured and spatially linked to tree canopy losses. Detailed statistics can be generated that summarise the extent of tree canopy gain or loss, as well as where it is happening within the community (private vs government vs community owned land). These statistics can be used to guide urban canopy management programs.

BEYOND URBAN FOREST MANAGEMENT LiDAR does not just image the urban forest, but it builds a detailed three-dimensional model of the entire urban environment. As well as vegetation metrics, individual building attributes and accurate terrain models can be derived from classified LiDAR point clouds using simple, repeatable methodologies. As a result, LiDAR can provide end-users with a much wider range of deliverables than information derived solely from two-dimensional imagery. This information can range from vegetation analysis for environmental management, individual tree segmentation for asset management, accurate building footprints for urban planning and high accuracy digital terrain models for flood modelling. When combined with RGB imagery, LiDAR can offer rich information and additional analyses for urban asset management.

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Digital Terrain Model (DTM)

Digital Surface Model (DSM)

RGB Imagery

Building Footprints

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BENEFITS OF AEROMETREX LIDAR Scalability: With fixed-wing aircrafts and airborne LiDAR sensors, Aerometrex offers you the most cost-effective method for mapping large urban areas. We have captured multiple council areas as part of single projects to drive scale & efficiency. Such scale & detail would not be achievable with other methods of LiDAR capture.

Custom end-to-end solution:

With our own aviation operations and in-house production teams, we can work with customers to customise data specifications and ensure it is ideal for the post-capture analysis. An end-to-end solution means greater efficiency which translates to best return on investment for our clients.

More than statistical estimates: Aerometrex provides complete spatial vector datasets that offer explicit locations and measurements linked to urban trees, as well as their surroundings. This provides greater flexibility to use the datasets, beyond just stats & numbers, to drive a robust urban forest strategy.

Quality & Accuracy: Aerometrex's LiDAR metrics help take the guesswork out of tree canopy management. Our high density, high accuracy surveys provide wide-scale data to create strong visual "alerts" and "comparisons" and take adequate & timely action. The sheer volume, intensity and accuracy of the data is a major time & cost gain compared to traditional land surveys.

In collaboration with the SA state government and sixteen local councils, Aerometrex recently completed a regional tree canopy assessment of Metropolitan Adelaide providing representatives across both levels of the government a robust benchmark dataset that can assist in the management of Adelaide's urban forests for years to come. Detailed vegetation analysis was carried out for all participating councils at a spatial resolution of 1 m to provide a detailed summary of the amount of tree canopy coverage across Metropolitan Adelaide, its spatial distribution and what land use and land ownership types it predominantly covers.

The analysis shows that 23.4% of metropolitan Adelaide is covered by tree canopy, with an average tree canopy coverage of 23.2% across participating councils. A comprehensive statistical breakdown of the types of land use and land ownership classes that tree canopy covers, across the study area, also indicates that the greatest opportunity to meet the 30-Year Plan for Greater Adelaide's target of a 20% increase in urban green cover by 2045, is on private land.

The results of this study can be viewed online within the Department of Environment Urban Heat and Tree Mapping Viewer. They provide management groups across multiple levels of government invaluable information that will help guide their tree management practices and provide a benchmark dataset to measure the change in tree canopy cover across Adelaide in the years to come.

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The Metropolitan Adelaide urban forest project was a valuable opportunity to collaborate closely with the State Government as well as numerous separate local Councils. It allowed us to develop our capabilities in order to produce information that is tailored towards a wide range of end-users and provides actionable information across a range of scales. We are proud to have been involved in a project that has provided management experts with a robust benchmark dataset that will provide positive outcomes to the Adelaide community. 11 Dr.Samuel Holt, Research & Development, Aerometrex.

Listen to Fabrice Marre and Dr Samuel Holt from the Aerometrex R&D team speak about urban forests and how our LiDAR services can help monitor and manage tree canopy cover within the urban environment.