A communication transmitted from Louis A. DePasquale, City Manager, relative to Awaiting Report Item Number 18-56, regarding a report on LiDar and Tree Canopy Studies

July 2, 2018 To: Louis DePasquale, City Manager From: Owen O’Riordan Commissioner, DPW Iram Farooq Assistant City Manager, CDD Mary Hart IT Director Re: Council Order 18-56 LiDAR and Tree Canopy Studies. LiDAR (light detection and ranging) is a powerful remote sensing surveying technology, typically operated from drones, airplanes or satellites. It is used to capture large data sets of feedback information that are then used to develop highly accurate topographic maps, high resolution 3D surveys and can be used in analyzing various landform attributes, such as buildings and trees. Over the past ten years the City has been involved in three LiDAR flyovers in 2009, 2014 and most recently in April 2018. The LiDAR data from 2009 and 2014 was used to produce the two tree canopy reports provided to the City by the University of Vermont (UVM) Spatial Analysis Laboratory. The study associated with the 2014 flyover indicated that there was a 2 percent loss in the overall area of the City covered by canopy between 2009 and 2014. This translates to a 7 percent loss in tree canopy relative to the canopy that existed in 2009. It is expected that the results of the tree canopy analysis associated with the April 2018 flyover will be finalized and available in the spring of 2019. In the meantime, the Urban Forestry Master Plan is presently underway. One of the more significant analytical tasks undertaken by the consultant associated with the project is taking the recently collected LiDAR information (April 2018), together with a geospatially generated random sample set of tree data collected by the consultant team to assess tree health on both public and private property. The random sample will be used to ground truth/calibrate the information taken from the LiDAR data. It is expected that this data will be cross referenced with species type etc. to garner a deeper understanding as to what and why trees are thriving and what and why trees are not. Additionally, the Department of Public Works has been utilizing the Cartegraph software system over the past year and six months to keep records of public trees throughout the City. This geospatial database is being used to store information specific to tree well location, tree well occupancy, tree planting, pruning, watering and any additional survey data gathered over the course of the life of a tree. All the various tree planting and maintenance contracts have data gathering specifications requirements at this time and this will generate a significant volume of useful information

in the future that will provide greater insight into where success is being had and where such continues to be a challenge. Obviously, LiDAR technology has many applications beyond tree canopy mapping, most particularly in 3d mapping and in transformative applications such as autonomous driving etc. On that basis the City’s IT Department would, working together with MassGIS and other interested parties expect to collect LiDAR data on a frequent basis perhaps once every 2 to 3 years moving forward. Furthermore, utilizing recently procured LiDAR analysis software and specifying the USGS data capture specifications, the City’s IT Department expects to provide more consistent datasets for consultants and others to work with providing a greater degree of confidence in changes monitored between one flyover and the next moving forward. Finally, It is readily agreed that LiDAR information is very useful is assessing the state of the urban forest at a given point in time and is also of benefit in being able to quantify the canopy gains and losses over time as well. Assessing the urban forest health should also consider improvements in tree planting and tree care practices and in procedures used to mitigate tree loss, be it due to development, storm damage, age or otherwise. These practices and procedures require a more extended period of time before they can be properly assessed and such need to be taken into account together with LiDAR studies when the overall condition of the urban forest is being considered.