Drones have become a valuable asset for the Gisborne District Council. with three machines proving their worth several times over. Use of the drones has grown extensively over the three years since the council got its first machine, says council principal scientist Murry Cave.
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The three drones are a DJI Phantom 4 Pro, a Mavic and a waterproof one.
The DJI Phantom 4 Pro, which cost $3500, is the council's most frequently used drone as it is compatible with aerial mapping software.
The smaller Mavic drone, worth $1500, is used for videos, while the $4000 waterproof drone is being trialled for flood gauging work.
“Getting a drone is a lot more cost-effective than getting one lot of images from satellites,” Dr Cave said.
“The principal areas we use them for are doing detailed mapping of areas where we have issues.
“For example, with the last wet weather events in June and July, we had a series of dams form across rivers.
“The satellite imagery available was poor quality but using a drone we were able to map the extent of the lakes that formed behind the dams and then work out the risks associated with a breach of the dam walls.
“Drones were used in remote areas where it is not possible to walk around the areas with a GPS (Global Positioning System) to map it.
“The drone takes aerial imagery that otherwise would cost the council around $5000, for a high resolution satellite image, or $600 to $1500 for a lower resolution image.
“In addition, satellite imagery may not be available for areas when we need them.
“We still use satellite image analysis but mainly when dealing with areas too large to fly with a drone and when the high resolution mapping from the drone isn't needed.
“Satellite analysis is being used to assess the change to large scale land erosion over time as a result of either increasing tree cover or where trees have been removed.”
Eamon Farrell is the council's primary drone pilot. He and Dr Cave are the only council staff with their CAA 101 qualifications. These are the Civil Aviation Authority's rules covering unmanned aircraft.
“Eamon does the flying — he knows exactly what he is doing,” Dr Cave said.
The drones came into their own when council staff needed to get a detailed look at slash on the Tolaga Bay beach.
“We routinely fly over the beach so we have an idea as soon as an event occurs about how much material is there,” Dr Cave said.
“It's detailed enough that we can see if there are fresh or old logs, and what type of wood it is. Once the debris has been put into piles we fly over again using software to determine work based on the volume of those piles, it's pretty accurate.”
Drones are also used as part of the Waingake Restoration Project.
“We are extensively using the drones to map the areas in the Waingake reserve to plan for restoration planting and see if there are any fractures in the forestry roads that need to be addressed or other issues that may need to be fixed.”
The drones are programmed to fly in a grid, taking hundreds of photos that create a high detail map of the area.
This will show the council areas in the land that are either low or high risk for land erosion.
“It is a very cost-effective way of getting new footage of an area in real time.”
The drones are also used for compliance monitoring.
Filmed and Edited by
Ben Cowper
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