Drones are an important new implement in the precision ag tool kit. They can be especially helpful when it comes to creating accurate field maps. But one of the keys to their effective use is making sure cameras produce usable, intuitive images.
By: Chris Bennett, Farm Journal Technology and Issues Editor
Agriculture technology’s quick-step march across farmland -- led by precision and automation – is fueled by results.
Brad Beutke of Crop-Tech Consulting, Heyworth, Ill., details hands-on advances in aerial imagery and UAV use in agriculture. "Aerial imagery continues to get stronger and we use high-resolution color photos, NDVI photos, thermal and satellite imagery, and UAV images."
One of the big questions surrounding yield maps is how to view data, according to Beutke. "Most software has a default setting of equal interval and that produces maps with only one or two colors. If you have NDVI with the legend set to equal interval, you may not be able to pick out differences. With all our mapping tools, we use an equal points or equal area legend to view data."
He stresses that resolution for any type of imagery is vital. The length and width of each pixel in the picture is crucial – the higher the resolution, the easier it is to pick out details.
"Typically that’s why we don’t like to use satellite imagery which can lead you in the wrong direction. It comes in 30 m or 50 m form and the quality is just not that good. At 5 m resolution we can see zones and where the water lays. At 2 m resolution we can see wheel tracks and small pockets in the field."
All the imagery that Beutke uses -- NDVI, thermals or color photos -- is done at 1 m or less. Because of the altitude at which an airplane flies, 1 m resolution is achieved as easily as 30 m, and both are cheaper than satellite imagery. As far as cost differences, the airplane images offer better resolution and lower cost, according to Beutke.
Beutke also relies on high quality color photos. Clouds can alter an NDVI reading and color photos taken at the same time are a remedy. NDVI can be backed up with color photos, and the same principal applies to thermal images. "We had a client come in and he had weird lines and what looked like crop circles. When we pulled up the color photos, the problem was revealed – shadows from windmills. He didn’t even have a windmill, but his neighbor did, and the shadow was showing up in the thermal imagery."
Beutke has collected imagery with seven types of drones at Crop-Tech – NDVI and video. A UAV can only fly at a maximum of 400 feet. However, at 400 feet, only a few acres can be taken in a picture, forcing reliance on special software to stitch images together. For Beutke, the processing side – stitching photos together – is the downside of drone imagery. Until a drone can fly at an airplane’s altitude, he doesn’t see drone imagery replacing airplane imagery. "Certainly drones are a tool we can use, but just not for large amounts of imagery right now. The way I think we’ll be using drones in the near future, until we can fly them higher, is for going out in the zones on airplane maps. Literally send the drones out to red, yellow or green spots on the map and have a look."
Beutke says no one should think they have to spend $30,000 on a UAV because most of the time a $500 or $1,500 drone will do everything a grower needs.