Aerial Applications

Many of us take the wind for granted—a shortcoming that can be costly for practitioners of precision agriculture.

Theirs is a world of efficiency and accuracy, especially as it relates to the proper application of plant nutrients or herbicides. As one agricultural engineer stated, “Everything we do is focused on getting the spray where we want it, and not getting it where we don’t want it.”

Those who rely on aerial applications, commonly referred to as crop dusting, must be intimately aware of meteorological conditions that could affect spray deposits and where they travel, especially wind speed and wind direction. “Most droplets tend to settle, but they still move with the wind,” says Brad Fritz, a research agricultural engineer specializing in aerial application technology. “It’s important for us to have a good record and understanding of what the environmental conditions are during each and every spray application.”

Weather conditions and forecasts are essential in terms of mission planning as well. “As someone who’s actually doing the application, knowing what the surrounding weather conditions are for the various fields that they’re going to make their applications on is key,” Fritz stresses. “They need to make educated decisions on whether the wind speeds are too low and we’re looking at very stable conditions with potential inversion, or wind speeds are too high that we exceed some of the pesticides’ product label and have potential danger for drift, then they have to make a go-or-no-go decision. Regardless, accurate data is key to this process.”

To obtain this data set, many applicators rely on information broadcast by regional airports or weather towers. Unfortunately, these towers may be thirty to fifty miles away from the fields where the solution is to be applied. To supplement this data, bulky cup and vane anemometers are ferried to the fields in an effort to provide users with relevant, localized information. These devices can be cumbersome to transport, so some applicators avoid them altogether in favor of the age old wind sock.

As a field research scientist, Fritz is always looking for solutions that optimize size, weight, and power variables. When a technician he works with told him about a miniature three-dimensional sonic anemometer that was soon to be released, his interest was piqued. He reached out to Stephen Osborn at Anemoment, the developer of the product called a TriSonica™ Mini Wind and Weather Sensor, to learn more about this unique offering. After an exchange of emails, Fritz was convinced that the TriSonica™ Mini was a workable, solid, 3D ultrasonic anemometer and that he needed to get one.

“The main feature that attracted me was the size,” recalls Fritz. “We’re going out into the field and having to record for two to four hours in a field study. Instead of carrying a lot of junk out in the field, like a big full-sized sonic anemometer with a mount and all that stuff, this fits in the palm of your hand. And then it was the price. It was quite a bit less than the full-sized anemometer that you get from companies that are out there.”

“As a researcher, I end up going to the field a lot to evaluate application systems in real-world conditions, which means, we’re taking aircraft out, applying sprays, and then with our measurement systems measuring where the spray deposits and where they travel,” Fritz states. “That requires a good measurement of wind speed, wind direction, temperature, relative humidity, that kind of thing. Before sonic anemometers, to get atmospheric stability we might have relied on a tower to obtain temperature profiles. Now with the three-dimensional wind sensor data we obtain, we can calculate turbulence intensity numbers to get a better understanding of what the stability conditions in the atmosphere are.”

Miniature ultrasonic anemometers are useful in a variety of applications where atmospheric conditions need to be monitored. Given their diminutive size they are well suited for portable, temporary deployments, while the fact they have no moving parts, thus eliminating maintenance issues, makes them ideal for permanent installations. Applications include airflow monitoring, weather reporting, ecosystem research, and the like.

“Having something like the TriSonica™ Mini, being fairly inexpensive, with the ability to do the turbulence calculations, I think would be a valuable tool for anyone involved in environmental monitoring,” speculates Fritz. “These guys are always pushing technology to see what it can do so. Here you have a small, field-deployable system that can be used easily and simply, while not taking up a lot of bulk. It is an inexpensive tool for gathering essential data that you don’t normally get from systems at this price point.”

Popular culture tries to convince us that Bigger is Better, yet this expression fails to address a wide range of real-time applications where size, weight, and power considerations are critical.

“TriSonica™ Mini replaces fairly bulky alternatives,” Fritz acknowledges. “Would a micro meteorologist use just one small sonic anemometer? Maybe not, but I’m an engineer looking for basic understanding of what’s going on in the environment. This single TriSonica™ Mini out in the field, with the temperature and relative humidity probe, is perfect for me.”

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