Ag Geek Speak

0.5 Tiny Bytes - Value of NAIP Imagery In Ag Mapping

• A Podcast for Precision Agriculture Geeks • Season 3 • Episode 1

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Sarah and Jodi discuss NAIP aerial imagery and why this high-resolution imagery is invaluable for precision agriculture work in the United States. They share workflows for validating zones, aligning layers, and spotting year-over-year patterns while noting timing pitfalls, thanks to NAIP imagery as a background source.

In this episode, we discuss...

• what NAIP is and who collects it
• benefits of high resolution often associated with newer NAIP imagery
• four-band imagery (RGB with NIR) enabling NDVI
• leaf-on timing and when imagery misleads
• state-by-state differences in resolution and frequency
• FSA and CLU uses that ensure strong georeferencing
• practical steps to draw boundaries and validate zones
• aligning offset satellite layers to NAIP
• leveraging multi-year NAIP to confirm stable patterns
• free access and where to get the data

Tune in next time for a Tiny Byte of knowledge from GK Technology, where we have a map and an app for that



https://gktechinc.com/

Sarah:

And now it's time for a Tiny Byte of knowledge. Hey Jodi, I'm just looking around at some imagery today. Do you know some good sources for some imagery as I'm trying to work with some of my agricultural data? What's your favorite place to get a background image?

Jodi:

Yeah, that's a very good question. And if I'm in the United States looking to do something with background imagery to make like a boundary on something that's really good and georeferenced, I will usually look for something called a NAIP image. What is a NAIP image? They are images flown by the USDA FSA, and they stand for National Agriculture Imagery Program. But in short, what they end up being are these four-band images that contain a lot of data and tend to be higher in resolution than what we can get for sentinel imagery. So they're an awesome tool for us to use, especially to have as a background map as we're making maps and uh looking for different layers to create zone maps, uh, drainage maps, et cetera.

Sarah:

Right. So this imagery is higher, uh, a better resolution, a higher resolution than a lot of the satellite imagery data that we're dealing with. If my memory serves me correctly, the Landsat data that we commonly use is 30-meter resolution. The sentinel data that we use is commonly 10-meter resolution data. And I believe the NAIP imagery is supposed to be mandated to be about one meter resolution. And you can find places where you can actually find even more detailed imagery than that if the state that you're working on has chosen to go to a higher resolution.

Jodi:

Absolutely. And as you mentioned, that there can be differences in terms of resolution between states. And I'll say this too: like even working with a one-meter nape image, it's really it's really nice compared to working with a 10-meter sentinel image. So even the one meter is very nice to have. But yeah, you can find all the way down to 0.6 meters and 0.3 meters. But another difference that you can sometimes find from state to state is the frequency of how often these are collected. Some states may collect them every five years or three years, or they may change the pattern in which they're collecting them. So they may go from yearly to every other year, et cetera. For example, in North Dakota, our North Dakota is kind of a special state in that for the last number of years, there have been nape images collected every single year, which is really nice to have as things change and move. But some states it's every other year, some states it's every three years.

Sarah:

That's really interesting. So some states you will get the frequency of imagery taken every year, and some states it will be every other year. Can you help me understand? I think you said something earlier about four bands. What does that mean to have four bands collected? Yeah, that's a really good question.

Jodi:

So when we think about what we're collecting when these photographs are taken, are bands of light. And the really common bands that we think of are RGB or red, green, blue. And that fourth band is the infrared band. And so with that fourth band, that allows us to calculate NDVI. And so not only are these background images really great just to have good photography of fields, but because they also have that fourth band, that infrared band, we can also calculate NDVI. So sometimes if the aerial image is taken during the part of the cropping season that would work well in a zone map, you could use that nape image to not only like make a background image, but also use that as a layer for creating a zone map or any other GIS image or GIS creation. But speaking about that, before we started this episode, we had talked a little bit about when they take these images, they usually try to take them leaf on. What does that mean? Leaf on?

Sarah:

The leaf-on portion of it, if you look at a lot of the data that comes from the from the USDA NAIP program, you know, for example, the information sheet that we found on the NAIP program from August of 2013, it talks about the NAIP program acquiring leaf-on aerial imagery, meaning that it's getting collected during the peak of the growing season, or at least that's the goal of when they're hoping to have these images taken. And that's a very important thing, especially if you are trying to get uh you use this imagery for vegetative indices, an indication of crop growth across the field. So that leaf on and the time of the year that they are taking, that imagery is still really important. Keep in mind, as opposed to our satellite imagery, again, the nape imagery is only taken one time a year. And the and and satellites are taking multiple times a year. So when I use nape imagery and making zones, I do like to try to kind of estimate what time of the year I think that image actually was taken and decide whether that whether that image does actually have value for describing crop growth in the field. I have seen nape images that are an excellent indicator of crop growth and can be a great descriptor of the variability of a uh that a field has. However, I have also worked with imagery that perhaps might have been taken immediately after a small grain harvest, for example, in which case the crop is already removed. Um, there might be a lot of other crops around that small grain field that are still very green in nature, but for the particular field that I'm working on that just had the small grains removed or taken off of the field, it's not going to be the greatest indicator. How does the USDA use the NAIP imagery for themselves? I mean, commonly, where do farmers end up running into nape imagery?

Jodi:

As a farmer, you might be familiar with the NAIP imagery as you know part of your background maps that you get from FSA. Um, when you go into certified certified acres and like confirm your common land units, the nape images that are collected are meant to help um supply the data for this. So that's where you'll probably see them as a farmer. And again, like if the FSA is trying to create those CLUs, they have to have images that are very geospatially referenced so that they can make those accurate and have good measurements because of that, as a side effect of having to have those images done for the farm program, um, we as geospatial practitioners get the benefit of having those really nice images to work with for our purposes too. Absolutely.

Sarah:

So, Jodi, in your practice of making maps and zone maps in particular, or drainage maps, or whatever kind of maps you're making, how do you like to use nape imagery as you're making maps?

Jodi:

I use NAIP, like as I think about it, I probably use nape more than I think I do, but it's it's always the image, or what I try to do is I try to use or find the newest nape image that has a good, good contrast between the boundary of the field so that I can draw the boundary for that field and then use that as use it as the official boundary for the field. And then I also like to use nape imagery, especially in states that have a pretty high frequency of them. So at least every other year, I like to just look through those images because they come in as RGBs in ADMS. So I like to look through those and look to see, you know, are there any common things that are popping up year over year? So I like to use this as a reference point. And then also to for some older satellite imagery from Sentinel and especially Landsat, if I'm seeing that there's some issues with like the Sentinel imagery, older Sentinel imagery, or where Landsat images not matching up to like where there's sloughs in the field, I will use a nape image that I know is georeferenced. Then I might move that sentinel image after I've already pulled it down from the online imagery library or elsewhere, just to match it up and make sure that things are lining up as they should. So that's I use the nape images a lot, to be quite frank. Um, is there anything else too that you use nape images for when you're making maps, Sarah?

Sarah:

I I think we use them very commonly together. It is my favorite layer to draw um tillage boundaries off of because they the the nape images are georeferenced quite well. Uh, and so I do I do find it to be the most reliable, the most reliable image to draw boundaries from. I also use them to help me uh evaluate how good my zones are that I have created. So I will usually download most of the napes that exist for a field that I'm working with and the proposed zones that I'm going to send out for somebody to look at before they're finally approved. I will turn those zones on over the top of the nape images and see how the variability components match up with what is in that field. It helps me to know whether I'm finding the areas of lower productivity or greater productivity. Though they will show up in the nape images very well. You will you will be able to visually see them many times. So it's very helpful from that standpoint. Keep in mind, this is very high-resolution data. It's very highly valuable data, and yet it is provided to us for free in the United States. So you yourself can go out and download this data. Uh, we at GK Technology have these data available on our servers. We've already downloaded it and have it available for you to use.

Jodi:

Or even though you know NAIP images aren't created for us to use as precision agriculture practitioners, it is a highly valuable data layer. And all of us that work in this line really should be taking advantage of it. It's a free asset, and we are extremely lucky here in the United States that that we can get access to it and have it readily available. Tune in next time for a Tiny Byte of knowledge from GK Technology, where we have a map and an app for that.