By: Andrew Hunt, Research Agronomist
Farmers increasingly rely on precision agriculture to help them save time, maximize inputs, and increase yields. So how does high-tech satellite imagery fit into the rapidly progressing field of ag technology?
While most agronomists and farmers will agree there’s no substitution for regularly checking fields in person, satellites are becoming a high-tech way for farmers to keep close tabs on their farms.
As technology improves, satellites can provide clearer images to give farmers a bird’s eye view…from space.
Find out if satellite imagery has the potential to help you check on your fields in ways that are out of this world.
How is satellite imagery used in agriculture?
Satellite imagery is a means to monitor crops and fields remotely over time. Farmers can use imagery to get an aerial view of various fields and crops to look for changes or differences. They can also use indices such as NDVI (normalized differential vegetation index) to monitor crop health, which allows them to make better decisions about where to scout fields or when and where to apply nitrogen fertilizer.
How has it evolved over the years?
In recent years, farmers have seen advances in satellite imagery with increased temporal and spatial resolution and improved accuracy.
Temporal and Spatial Resolution
There’s an increased number of satellites from which one can access these images, which increases the frequency of the number of images of the same location (increased temporal resolution).
In the past, people relied on a lengthy revisit time for just a handful of satellites. Revisit time is the time elapsed between two successive observations of the same ground point on the surface of the Earth.
As the technology improves, farmers have access to increasingly detailed images (spatial resolution) of their land. These improvements increase the details that one can interpret from the image.
Spatial resolution refers to the area of ground contained in one pixel. For example, a 30-meter resolution means a single pixel represents a 30m X 30m area on the ground, and anything less than 30m x30m will blend in with the surrounding area.
Positional Accuracy is the distance between the location of an object compared to the position of the object in the image. Positional Accuracy is dependent on several factors, mainly the terrain and the angle from which the image was collected. Areas outside of the center will appear distorted.
Some accuracy improvements come after the image is collected in a process called orthorectification, which removes distortion.
Advantages to satellite imagery in farming
With satellite imagery, farmers can save time and money with directed scouting when they know which fields need attention. They can quickly spot differences in a field, and even if the image doesn’t provide information for the cause of the variations, this is especially helpful when a grower has hundreds or thousands of fields to cover.
Satellites can help with decision making, but the value they provide is limited by who interprets the image and how they use the insights. So, they don’t fully replace the need for a boots-on-the-ground approach.
Challenges of satellite imagery
Usable or valuable satellite imagery is highly dependent on weather conditions, as clouds can completely obscure objects on the ground. Revisit time of imagery may not be favorable for specific needs, as the combination of weather and revisit time may increase the waiting time for a valuable image, which could be problematic. Also, spatial resolution and accuracy may not be high enough to provide the necessary detail.
Satellite imagery can help farmers monitor specific locations, but doesn’t necessarily explain what’s going on. For example, satellites can tell us that crops are unhealthy, but the reason why can’t always be interpreted from the imagery.
The use of satellite imagery will never replace a farmer’s need to check his fields in person, but it’s a helpful tool farmers can use to save time when evaluating the health of their crops.
As the technology continues to improve, and satellites provide clearer images, farmers should consider using satellite imagery on their farms.