Sometimes, 3 bands of imagery just isn’t enough. Sorry, RGB, you’re just not good enough! We came across this issue when trying to look at landcover for a forestry management client. Knowing that National Agriculture Imagery Program (NAIP) imagery, particularly the latest versions, comes with natural color/color-infrared (CIR) and has a decent resolution (1-meter) makes it very attractive for separating out vegetation from other types of landcover. It’s also sweet when you can find the CIRs for FREE! But there’s always a catch, isn’t there? Of course, there is.
Where to go?
The USDA NRCS Geospatial Data Gateway is a fantastic resource for downloading data, even NAIP. However, for reasons unknown to this blogger, you never get 4 bands. Know the answer? Post a comment below. After some research and failed attempts, I threw in the towel and told Randy that no free downloadable CIRs could be found, but that I did find a price list for ordering it. Don’t you know that my jaw dropped when the next email from Randy was a link to the USGS National Map with instructions on how to download NAIP CIRs. So here’s the secret handshake for getting a county’s worth of NAIP CIR goodness:
- Open the USGS National Map Viewer.
- Zoom into the general area/state of interest.
- Directly above the map, click on the Download Data button:
- Under the Download Options popup, go to Choose a reference area then click on Counties to select the county of interest in the map:
- In the Selection tab to the left, click on Download and, in the next window, check the box for Orthoimagery. Next, you will see the details for the NAIP imagery listed, including the dates of the imagery and a link to metadata info (example for Benton Co., TN) FYI: Depending on the dates listed, you may or may not get 4 bands. If you need more information for a particular location or date, you can get that from here. You will need to download the PDF for it to be interactive.:
- Check the box for the imagery you want then continue through the checkout process. You will need to provide an email address to receive an email with links from which you can download the imagery.
What next? Here’s the gotcha.
For the example above, we got an email for our county of interest that included 60 links from which our imagery needed to be downloaded. Evidently, the imagery gets sliced up into these 18.6 MB chunks which is a bit inconvenient but again, it’s FREE! I really didn’t want to click through each of these one at a time. We use Google Business Apps for our email so I looked around for an add on for Chrome that might help me out. Unfortunately, the download managers for Chrome weren’t really helpful for looking inside of an email. Fortunately, FireFox does have an add on that can look inside of email, DownThemAll! is the time saving ticket. Once you have your email open, you can right click in the email to select the DownThemAll! add on. It will show you all the download links from the webpage and gives you the option to check mark the ones you want. Just check all the image links then continue. It even provides you with a pleasant sound alert when finished. Below, you will see a screenshot from ArcMap showing that all 4 bands are present:
Now you are ready to mosaic the group of images together and start enjoying your NAIP imagery for your next landcover project.
Happy GISing!
