GIS/GPS/Chattanooga, Tenn., builds tree inventory
Using global positioning satellite (GPS) technology, Chattanooga, Tenn., has created an inventory of the nearly 6,000 trees located in and around its central business district (CBD). The inventory will help the city plan tree maintenance in the area and is a component of the geographic information system (GIS) that the city shares with Hamilton County, Tenn.
The information replaces an out-of-date inventory that the city compiled more than a decade ago. That inventory was not part of the GIS and was stored in a software program called Tree Manager.
To build the new inventory, Chattanooga’s Urban Forestry Division borrowed a GPS backpack unit from Hamilton County. Just after Labor Day 2002, workers began to walk through the CBD and record information about trees into the GPS device. By the end of last year, the data collection was complete.
The inventory includes the location of each tree, as well as its species, tree-pit dimensions, irrigation status and trunk diameter, says Gene Hyde, city forester for Chattanooga. The city spent roughly $7,000 in labor to assemble the information, Hyde says.
The rebirth of Chattanooga’s downtown in recent years helped spur Hyde’s decision to create the tree database for the GIS. With the CBD becoming a popular destination for residents and visitors, maintaining the health and appearance of the trees in the area is crucial, Hyde says.
By studying the tree data contained in the GIS inventory, forestry employees can map out a maintenance program with a greater degree of precision than ever before, Hyde says. Prior to the new system, determining the time and money necessary for tree maintenance was “more of a shot in the dark,” he says. “For each [tree-trunk diameter classification], there is a standard number of man-hours for pruning that sized tree. You can then start to project what the man-hours for maintenance will be and what the cost projections will be. That was basically our number one goal: develop an overall management plan and see what it’s going to take to maintain it.”
The inventory also helps the city keep track of species diversity among the trees. “You really shouldn’t have more than 10 percent of any one species in an area,” Hyde says. “Otherwise, you’re risking getting overloaded on a particular species. Should an insect or disease come through, it can wipe [a tree population] out.”
Giving other city departments easy access to tree data was another reason behind the creation of the inventory. For example, through the GIS, city planners can examine the tree information when they are evaluating proposals for development in and around the CBD.
The inventory’s GIS format will allow it to be a component of future technology initiatives. For example, the city is considering installing a comprehensive, GIS-based work-order management and tracking system that would incorporate the information contained in the tree inventory.