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T&D > Programs Areas > Inventory & Monitoring > Aerial Vegetation Survey Program Areas
Aerial Vegetation Survey
Ryan Becker, Project Leader

Build Versus Buy

A surprising number of companies offer autonomous flight control systems or do-it-yourself UAV "kits" for sale. Given that these kits can cost as little as a couple thousand dollars, attempting to build a very low-cost platform for the mission was an option within the scope of the project. Several factors led to the rejection of this possibility. Similarly, the Bat is also a commercially available package, but the information gathered during the project indicates the greatest value to units seeking such data dictates that interested parties simply contract for a data product rather than purchase the aircraft. While the combined data product needs of the Forest Service represent a large potential market for UAV operators, individual units are not likely to ever see a return on the investment once training, maintenance and operational costs are added to the purchase price of the UAV.

Autopilots, Kits

GPS receivers are at the heart of modern autonomous flight systems. Some autopilots use hundred-dollar handheld units with a serial output to the software, while others integrate the receiver directly onto the circuit board for extremely low weight and power consumption. The cheapest systems available rely entirely on GPS data for flight control; these are entirely unreliable, as the aircraft loses all directional control with any GPS outage. Reliability is only possible with the additional inputs of airspeed, three-axis orientation, and magnetic heading. All the UAVs investigated for this project used these inputs, and none of the operators reported flight failures due to loss of GPS.

Of the systems incorporating all required inputs, most also require additional programming, or "learning flights," to incorporate important parameters such as minimum and maximum airspeed, trim values for level flight, and turning limits. These systems are typically not designed for autonomous takeoffs or landings, and only a few include an additional output that can be used for triggering a camera. Only one located during the project can save a continuous record of GPS position, a critical component of developing accurately georeferenced data, although it is possible that software could be developed for relatively low cost to save the data transmitted to the base station with other systems. An onboard record is preferable, though, since the radio downlink is unreliable. The Micropilot MP2028g appears to be the only system that meets all the practical requirements of a stand-alone autonomous flight controller. Micropilot also offers a fully autonomous UAV incorporating this controller with software for a laptop base station for less than twenty thousand dollars, but the aircraft is only capable of ten to twenty minute flights on a full tank of gas. The Bat has already been designed and optimized for missions such as this, so system development has already been paid for.

A scale measures weight.

Buy and Fly?

UAVs are deceptively simple to operate. Their operating costs, while generally much cheaper than comparable manned missions, are high enough to prompt the question whether buying the UAV outright would bring long-term savings. The answer appears to be no, once all contributing factors are considered.

FACTOR: Training. MLB includes five days of training in the purchase price of the Bat. The training encompasses all the aspects of UAV ownership and operation to help owners avoid the most common mistakes new aircraft operators make. Given the replacement cost of the Bat, operators have no room for human error in mission planning and execution. The tasks involved in flying any UAV are complex enough that operators are encouraged to maintain proficiency with regular flights. Contracting with the UAV operator for a data product eliminates the need for initial training, as well as refresher flights.

FACTOR: Flight planning and data reduction. In order to contract for a data product, the land manager only needs to specify the areas to be mapped with GPS coordinates and the desired resolution. The UAV operator must combine this information with a Digital Elevation Model of the area to plot specific flight lines and altitudes in the planning software, identify when the image memory will fill up and require interruption of the mission, and optimize all the individual flights; a process that requires between several hours and several days, depending on the complexity of the mission. The raw data requires considerable manipulation before it can be mosaicked, and given the results of the mosaicking trials conducted during the project, the process will require considerable manual effort until the FAA allows higher UAV flights. Contracting for the data product embeds all these costs into the fixed price and places the responsibility for quality control on the operator.

FACTOR: Maintenance and repair. A UAV requires periodic maintenance and repair, and software is occasionally upgraded or bugs fixed. UAV operators factor this cost into standard service rates, which spreads the cost across all contracts. Contracting for the data product eliminates the need to deal with this factor.

FACTOR: Security. The UAV package is considered sensitive property and must be accounted for. Since any UAV consists of multiple components, usually including a laptop, video recording equipment, and wireless data transciever, all the components must be tracked. Occasional use of the entire UAV package could encourage use of the other components for unrelated work when the UAV is not flying, increasing the risk of loss.

FACTOR: FAA rules. Even though UAVs currently fall into the same category as hobbyist model airplanes, operators must avoid restricted airspace, such as near an airport or military base. Operators must also comply with any special FAA directions, which requires the active participation of the operator. Once the FAA approves rules allowing UAVs to operate above the current flight ceiling, operators will need to follow an as-yet undecided procedure for obtaining clearance for the proposed flight. Such specialized knowledge and tasks will be easier for professional UAV operators to follow.

As may now be obvious, in addition to the initial acquisition cost of the UAV, an organization purchasing one will basically need to dedicate the majority of at least one employee's time to UAV-related tasks. Someone will also need to be skilled in the tasks required for image manipulation, and subsequent repair or security costs simply add to the total continuous cost. The economics of owning and operating a UAV clearly favor the full-time user.