Cities Branch out to Trim Trees

New workflow tames hazardous vegetation

Trees growing in a pedestrianized area of Moncton.

Dan Hicks, director of operations for the Parks Department in Moncton, New Brunswick, Canada, oversees several city assets from arenas to forestry. Every municipality has standard operating procedures, and when elements of these processes are automated, efficiency and reliability grow. Hicks and his team correctly predicted that a certain routine maintenance task—identifying and recording low-hanging tree branches—was ripe for automation. A hazard to vehicles and pedestrians alike, low-hanging tree branches require continual identification and removal to ensure people can safely navigate the city. In the city of Moncton, tree branches must be 15 feet (4.6 m) above street level and 8 feet (2.4 m) above sidewalks.

When Hicks described the traditional method of recording low-hanging tree branch locations, the opportunity for improvement became evident. “We did it before by driving past, jotting down addresses and identifying low-hanging branches by eye,” said Hicks. “It’s time-consuming when you do it that way, using pen and paper and driving. Drive, stop, write it down. Drive, stop, write it down.” Hicks and his team knew a more automated solution was possible. They presented the challenge to the team at Cansel, their Trimble distributor, who assured Hicks that they could figure something out.

LaserTech TrueSense S230 mounted to front passenger window of car; Trimble Catalyst DA1 antenna mounted to car roof; mounting by suction cup in both cases.

Cansel provided them with a simplified mobile scanning device made up of three basic elements. Attached to a company vehicle, a small lidar unit – a LaserTech TrueSense S230 – measures the clearance to the nearest solid overhead structure while a Trimble Catalyst DA1 antenna defines the vehicle’s horizontal location to sub-meter accuracy. A Samsung tablet with a customized software application developed by Cansel handles the data from these two elements and delivers the output file.

Catalyst, Trimble’s subscription-based GNSS service for Android, turns the Samsung tablet into a fully functioning GNSS receiver, providing positioning at sub-meter accuracy without the expense of traditional GNSS equipment. Using a tablet (or smartphone) as a GNSS receiver makes this setup more approachable for employees who have no experience using survey equipment. Anyone familiar with a smartphone can navigate the software on their Android device. The small DA1 antenna and lidar unit are mounted by suction cups, making the setup easily transferable between company vehicles. “You can put it on a golf cart and measure clearances on sidewalks,” Hicks said. “You can mount it to just about any type of vehicle.” Currently, the setup is attached to the truck of a foreman who gathers the tree data as a supplemental task to his normal duties.

Samsung Android tablet in use while connected to LaserTech TrueSense S230.

When the drive is over, the customized application exports a comma-separated-values (CSV) point file to the city’s GIS technicians, who upload the data to a city map in Esri® ArcGIS®. Hicks and his team review the map, then filter and sort the conflict areas as high-, medium- and low-risk sites. The GIS map allows them to assess and schedule the maintenance of these conflict areas most efficiently, so they can attend to high-risk sites before they become a problem for motorists.

Hicks and his team are enthusiastic about the prospects of this new solution. Its simplicity allows employees without GNSS expertise or forestry knowledge to use it, which means purposeful, non-specialized work is available to more people. “You’re looking at a municipality with 650 employees, and at any given time some of them are on modified duty,” Hicks said. “They might be able to drive a truck but not lift a chain saw, so we need productive work for them to do.” The ease of use makes this a task that any employee capable of reading a tape measure and driving can perform successfully.

The subscription-based GNSS capability provided by Catalyst also allows flexibility in planning when gathering data, without a substantial investment upfront.

“One could collect data several kilometers per day,” Hicks said. It’s a clever upgrade that will benefit both the employees of Moncton and the citizens they serve.

Gordon Wilson is a professional land surveyor and writer living in Portland, Oregon.