How to Use Imagery to Your Advantage
I’m Will Mullenix. I’m a Grower Advisor with Growers Axis® based in Iowa. My job is to provide unbiased advice to growers on all aspects of production agriculture.
Have you had a bad experience of imagery in the past? Maybe it was poor resolution. Maybe there was no follow up when you received it.
It’s important to keep in mind that not all imagery is created equal. I’m going to talk about three aspects of imagery.
First is: Resolution differences of imagery types.
Next, is: What does imagery show?
And then: How can you use it?
Aspect #1: Resolution Differences of Imagery Types
Not all imagery types are created equal. And that’s based on the resolution of the imagery. A lot of imagery comes available from different vendors that is satellite captured imagery, and typically, this is low resolution, maybe 10 or 20-meter resolution, which is not very high. And I think about resolution myself understanding the importance of it when HDTV first came into the marketplace, and this is way back in, I don’t even remember when, around year 2000. And you know, at first, when I heard about it, I thought why in the world would you want HDTV? Well, this is 20 years ago, and I could see better than I do today. I didn’t need cheaters, but when I got HDTV, I’m a sports fan; it made the experience better. And today, when my HDTV signal goes off, and I’m watching the Cardinals or some other sporting event, I can’t even see the screen. So, resolution matters, and even more so with imagery.
Aspect #2 What Does Imagery Show?
What does imagery show? What are you looking at when you look at an imagery event for a field? And basically, imagery is showing light reflectance off the canopy. Or, another way to think about that is canopy density.
Every image should have a scale from low to high. Sometimes they have numbers involved; sometimes, they don’t. But low reflectance means low canopy density. The leaves aren’t very thick; the plants are shorter, the leaves are smaller, the yield potential is less. High-density areas, high reflectance areas have dense canopy, bigger plants, bigger leaves, more yield potential.
Reflectance of crop canopy indicating crop density are what you see; that’s the take-home message from an image.
This is showing two different imagery sources for the same field (see 3:23). The field is located in West Central Iowa. The imagery on the left is UHR imagery, and this is very high resolution. This is the imagery type that Grower Advisors use most often. It was captured with a fixed-wing or an airplane. The resolution of this image is a few centimeters. So that means if you zoomed in and saw the pixels, they’re really close together, and there are more of them on the screen.
The image on the right is satellite-derived. And I don’t know the exact resolution, but it’s probably somewhere between 10 and 20 meters. So very different from the image on the left.
And one of my counterparts uses this imagery to decide where to go scout in this field. And he went to the red areas on the left image. Well, if you were using the image on the right, keep in mind the scale is different, green is low reflectance areas, red or pink are high reflectance areas, but unless you went to the green spots, you would be in a totally different area of the field, then the decision you made based on the high-resolution image on the left.
So, there’s an example of why your source and your resolution level and how important it can be.
Aspect #3: How Can You Use Imagery in your Operation?
The third point is: How can you use imagery in your operation?
Well, if every field you farm was uniform, and if the density of the crop was always high, then guess what? You don’t need imagery. You don’t need VRT. You don’t need to do anything different on one corner of the farm from the rest. Some fields are like that. But most farms aren’t. Most times, imagery is going to show variability on the farm. And unless you go look, you’ll never learn why those areas are different. It could be an inherent characteristic of the field, eroded soils on the side hill, or a wet area in a in a prairie pothole region in Northern Iowa, for example, that’s flooded or wet. But unless you go look, you don’t know. And the value of looking can be very large. You could go to high-density areas for yield estimation in early August.
What’s the Value of Understanding How Good the Crop is?
Maybe you still have marketing decisions to make. You typically have a better marketing opportunity in the late summer than you do late in the fall or the early winter. So, you can market ahead.
Maybe there were weather events that went through, or you wondered if there were weather events. How often do you find green snap corn, lodged corn, with the corn head when you’re harvesting? Wouldn’t it be good to know in August if there’s been a wind event so that you could harvest stress fields or wind damaged fields earlier so that you reduce your field losses?
Increase Your Farm’s Profit
And maybe your farm has the potential to increase profit from variable-rate seeding, fertility, or other inputs.
Using imagery to understand variability on the farm is a highly effective practice. And keep in mind, it’s a preview of the yield map if you have a good enough resolution image.