The layers in our LandSat image are:
| Layer number | Wavelength band (µm) | Name |
| 1 | 0.45 - 0.52 | Blue visible light |
| 2 | 0.52 - 0.60 | Green visible light |
| 3 | 0.63 - 0.69 | Red visible light |
| 4 | 0.76 - 0.90 | Near infrared |
| 5 | 1.55 - 1.75 | Mid-infrared |
| 6 | 10.40 - 12.50 | Thermal infrared (useful for surface temperatures, but not so useful for visualizing land cover) |
| 7 | 2.08 - 2.35 | Mid-infrared |
Currently, the monitor's Red channel is displaying the image's Layer_1, the monitor's Green channel is displaying Layer_2, and the monitor's Blue channel is displaying Layer_3. Basically, ArcMap just assigned the layers to channels in numeric order.
But, if you look at the table of bands in our image (above) you'll see that while Layer_2 is green visible light and is correctly assigned, Layer_3 and Layer_1 are backward - Layer_3 is actually red visible light, and Layer_1 is blue visible light. If you look at the image, this mis-assignment of layers to channels gives us colors that are all messed up. We can fix it.
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1. To make a natural color image, we need to assign Layer_3 to Red, and Layer_1 to Blue. Like in the animation to the right, click on the Red channel and select Layer_3, and click on the Blue channel and select Layer_1. Green is already assigned correctly, so no need to change it. You now have a natural color image, which looks like a photograph taken from space (because that's basically what it is). |
Try some panning and zooming, and see if you can identify some features on the image. If you turn the composite_november_2011.img on and off you can see the high resolution imagery behind it, which will help you confirm that you're seeing what you think you're seeing. Try to find:
Before you move on to the next step, you can right-click on the composite_november_2011.img image and "zoom to layer".