One of the powerful remote sensing tools available in Adobe Photoshop is to detect the land surface information by creating a false color composite image. Multispectral images contain the reflectance information from the visible and invisible electromagnetic spectrum. Using this information, we can detect many kinds of land surface information. For this example, we will detect the green area using Landsat images imported by Geographic Imager for Adobe Photoshop, which ensures all the georeference information is maintained.
Landsat images consist of several gray scale images, with each image containing one of the bands of the electromagnetic spectrum. For example, in the Geographic Imager tutorial folder, there are a set of Landsat images available. Those gray scale images are from Band 1, 2, 3, 4, 5, 7, and 8.
These images need to be combined into one image. The Adobe Photoshop function called “Merge Channels” produces one image by combining mulitple gray scaled images. With this example, those gray scale images from Band 2, 3, and 4 will be merged into one image by assigning a color for each band.
1) Open the Landsat image from Band 2, 3, and 4. Note that the Geographic Imager panel shows the information on the coordinate system and image extents.
2) Open the Channel panel (Window > Channels). Choose “Merge Channels” from the panel options menu.
3) In the Merge Channels dialog box, select RGB color as the mode.
4) In the Merge RGB Channels dialog box, specify the band for each channel: band 4 for the red channel, band 3 for the green channel, and band 2 for the blue channel.
5) As a result, those three images from Band 2, 3, and 4, are assigned to the Blue, Green and Red channels, respectively.
6) Now, let’s take a look at the image!
This combination of false-color makes vegetation appear as red tones. The bright red color indicates the growing vegtation. Water is displayed in a blue color. When the water contains high sediment concentrations, the color will be lighter blue. Urban areas will appear gray to blue-gray in color.
7) All the georeferenced information is inherited by the new image with merged channels from those original images. The georeference information is displayed in the Geographic Imager panel.
