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Satellite and aerial images can be useful field tools, but especially so when their data is backed up with observations from the ground, a Calgary geo-coach told farmers at Agri-Trade.

Warren Bills, business operations manager with Agri-Trend Data Corp., gave a presentation on these tools during the farm show at Red Deer's Westerner Park.

Variability seen from the air allows farmers to make informed assumptions; "ground-truthing" can then help them generate hard facts about their fields' health, Warren Bills says. -- Alexis Kienlen photo

High-altitude images can identify field variability, he said. These tools can measure plant density, plant health and soil moisture levels, which then help determine soil health.

Photos taken from a plane are referred to as aerial imagery. This method offers a lot of control, as well as high-resolution photos from below cloud cover.

Agri-Trend works with Rapid Eye Satellite Imagery, which has launched five satellites used for agricultural imagery. The satellites, however, are above cloud cover so they can be affected by weather patterns.

The satellites orbit on a five-day cycle and can be good for monitoring patterns over time. The satellites can also detect small changes in vegetation health, based largely on their readings of chlorophyll content in plants.

Satellite imagery captures pictures of how the sun's wavelengths are reflected back from the earth. The light reflects at different-coloured wavelengths, depending on what the sunlight hits when it gets near Earth's surface.

Satellite tools, Bills said, need to be used with a process called "ground-truthing."

"This is absolutely crucial. Sometimes we've had an image come back and we make some assumptions based on that image," he said. "We need to get out to the field to see what is happening."

Farmers who are ground-truthing walk their fields equipped with printouts of their satellite images and either a GPS handheld system or a map and marker.

"Unless you do this, you're going to miss a lot of the insight that you gained from the imaging," said Bills.

Ground-truthing, combined with soil sampling, can help identify the specifics in sections of the field, which can result in better management decisions.

"One of the things you can do is create management zones, by breaking the field into sections," Bills said.

-- Alexis Kienlen is a reporter with Alberta Farmer Express in Edmonton.