Course 1C - Downloading Free High-Resolution Imagery from The National Map (USA) for a Base Layer in GIS
The point of this course is to explain how to download high-resolution imagery so it can be used as a base layer for satellite and elevation data. It is important to have high-resolution imagery (1-meter resolution or less for the purposes here) to understand satellite data better (10 to 30-meter resolution for the purposes here). You may already have imagery for this; if so, follow along to make sure there is not better imagery available through the steps in this course. The faster the internet speed for this and other viewers and downloads, the smoother the process should be.
1) Open the Data Sources folder to the left and click The National Map link.
2) A new window will open with the following page. Click the "New TNM Viewer" graphic on the right (the link should automatically open to this page in the near future).
3) A window will open to the following map viewer. Click "Link to Data Download" on the upper-left menu.
4) The page will change to the following.
5) Navigate to an area of interest by scrolling or use the "+" icon. It may be difficult to find the area you want with the topographic layer as the base map. The base map can changed to imagery, which can make locating a specific area easier (this will be shown in next two steps).
6) Click the Base Map Layers icon:
7) Click "USGS Imagery Only" and the base map will change to imagery. This is not necessarily the imagery that you will download.
8) At this point you want to select the area that you want imagery for (a field for example). Click the "Box/Point" button.
9) Drag the cursor to make a box around area of interest. If you have drawn a box but want to draw a different one, click the "Current Extent" button and the box will be cleared - you can then draw another box. There are other ways to extract data for a particular extent, but just the "Box/Point" method will be used here.
10) Select an imagery type by clicking a box in the Data section on the left panel; when selecting, a map will appear that shows where that type (resolution) of imagery is available. After selecting a type available for your area, click "Find Products".
11) After clicking "Find Products", the panel on the left will change - it will show data available for your search box. The right part of the panel is shown below. If you click "Footprint", the extent of that imagery will appear on the map. "Info/Metadata" includes important background (metadata) information for the imagery which will be explained in Course 1D. You can download the imagery by clicking "Download", but there is an advantage to clicking the "Add this item to the cart" icon, then downloading - wait until Step 12 before clicking it.
12) If this is for crop agriculture purposes, try to get soil imagery. The "Metadata Updated" date can give you a clue as to whether and image shows soil. Click the icon to add the imagery to the cart for dates that seem to represent soil imagery. Click "View Cart" (not shown in graphic; it is above the cart icon on your screen).
13) After clicking "View Cart", a window will appear that previews the image that you can download. If you click on the "Preview" image, it will expand so you can get a larger view. Take some time here to familiarize yourself with the map viewer functions. You can download from this page, as is shown in Step 14.
14) Download imagery you are satisfied with. As was emphasized in Course 1A, make sure your internet browser is set to ask where to download, so you can locate/organize downloads properly on your computer.
15) After finding the downloaded compressed (zipped) folder on your computer, extract it (to open it) by right-clicking on it. After extracting, you will be able to open imagery in GIS software by adding the .jp2 file. Keep in mind that most imagery from The National Map is in JPEG2000 (.jp2) file format. (If you need decompression software, we recommend free 7-Zip [outside page; opens in new tab]).
Soil Imagery for Field Shown Below (two images were needed)
