## 3 Data-Collection Platforms and Instruments
### Sensor Deployment and Operation over Vegetation Canopies: A Basic Procedural Philosophy
In concert with the development of the backpack, a similar packaging architecture was applied to instruments used for limnological studies (e.g., assessing the quality of surface waters). Figure 1: Corn canopy imagery taken by digital camera from the boom of the field platform; (**a**) 19 June 1998 and (**b**) 20 August 1998. Figure 3: Wireless instrument backpack and instrument pole. Note the up- and down-welling fibers at the end of the pole and the spectral radiometers at its base. Figure 2: Block diagram of backpack components. Acquiring Spectral-Reflectance Data at Canopy and Plant Community Levels: The Hercules Motorized-Vehicle System with Wireless Communications  
In 2008, the research team created a versatile, all-terrain platform, affectionately known as \"Hercules,\" to facilitate in-situ data collection in a repeatable, scientifically valid manner (Figure 4). It constituted an attempt to address all of the necessary considerations and procedures for collecting science quality spectral data (summarized in Section 2.0). The platform is based upon the successes achieved with an earlier version of an all-terrain motorized platform [8]. The base tractor for Hercules was the prototype used in the development of the Hagie (Clarion, IA, USA) STS series of self-propelled spray coupes. A rear-mounted 365 hp turbocharged Cummins diesel engine powers a joystick-controlled, 3-speed, hydrostatic 4-wheel-drive propulsion system. Hercules is capable of reaching speeds of 45 kph, which greatly enhances research productivity because no trailer is needed to travel between research fields. Hercules weighs nearly 9000 kg and is 3.7 m wide, 3.5 m high, and 7.6 m in length. It has a turn radius of 5.5 m and under-frame clearance of 1.8 m, which facilitates data collection in tall, late-season crops. Instruments for data collection are deployed on a center-mounted boom located immediately behind the cab (Figure 4). Multiple hydraulically activated articulation points and a full 360-degree swing arc enable the operator to position an instrument package in a range of heights from centimeters above the ground to approximately 12.8 m at maximum extension. The main boom section (6.4 m long) has a maximum lifting capacity of about 454 kg. A manually extendable, multi-position jib of 6.4 m is available for adding length to the boom, but reduces the payload to 68 kg. Other assorted features include remote boom control (within 152 m), adjustable tread width (3 m to 4 m), and independent air-ride suspension between cab and payload platform. Figure 4: The Hercules research platform shown was configured for making hyperspectral observations. The self-leveling sensor frame is seen at the upper right. The frame includes up- and down-welling optical fibers, GPS antenna, infrared thermometer, pyranometer, quantum sensor, and down-looking digital camera. The Hercules Instrument Box is located just to the left and below the sensor frame. The electronics and instrumentation configuration on Hercules builds on experience gained with \"Goliath,\" the earlier, smaller, machine, which had many cables running up and down the support boom in order to interconnect instruments and the control/data acquisition computer. Despite care taken when clamping and positioning them, there was a high probability that cables would be pinched, or even severed, as the boom was extended or rotated. The instruments on Goliath were shared with other experimenters; hence connectors were mated and separated at least weekly leading to physical damage due to wear and bent pins. Goliath was also equipped with a ruggedized desktop computer. Long exposure to sun and high levels of vibration damaged adapters and hard drives in that machine. The instruments and electronics on Hercules were, like the backpack described earlier, integrated into the \"Hercules Instrument Box\" (HIB), and connected via WiFi technology with a cab-mounted computer (or a laptop in the field, as needed) Figure 4 depicts the instrument boom positioned to acquire data.