The goal of this lab is to show how to delineate a study area from a larger satellite image, demonstrate how spatial resolution of images can be optimized for interpretation, use radiometric enhancement techniques in optical images, linking a satellite image to Google Earth, explore various methods of resampling satellite images, image mosaicking, and use simple geographical modeling to detect binary change.
Methods:
Image Subsetting:
Using ERDAS Imagine 2016, subsetting an image is simple. After the image is brought in, simply right click, use the inquire box tool, set the box over the desired area of the image, then use the subset and chip set of tools to create subset image. This opens a new window that lets the user save the subsetted image to a new file. Simply click "from inquire box" and okay and a new image is created from what subset. If a square is not the right shape for the area that is being subset, a shape file can be imported and used as the area of interest.
Image Fusion:
This can be used to pan sharpen images and give them higher resolution. To pan sharpen the resolution merge function can be utilized to combine a reflective band image with a panchromatic band image to create a higher resolution image. Both images are input to the function, the user names the output file and selects the method and resampling technique and then runs the function. The resulting image will have a better resolution.
Simple Radiometric Enhancement Techniques:
Haze reduction helps an image look crisper and makes it easier to view. Using the haze reduction tool under the raster settings, the user inputs the image that they want the haze to be reduces, name an output file name and click run and the tool reduces the haze in the image.
Linking Image Viewer to Google Earth:
Linking the ERDAS viewer to google earth is a good way to get another view of the image being examined. ERDAS has a google earth function that makes this very easy. All the user has to do is click the Google Earth tab at the top and click connect to Google Earth. This will open a new window and then can be open side by side. ERDAS and Google Earth can be matched and linked by clicking, match GE to view and then syncing them together. Google Earth has very high resolution and labels making it useful to identifying objects being examined.
Resampling:
Resampling refers to changing the size of pixels in the image. This can be useful if the user wants to run a function where two images need the same pixel size. To do this the user goes to spatial under the raster tab, then clicks on the resample pixel size tool. This opens up a new window where the input and output and new pixel size can be entered. The user then clicks ok and the program is ran, changing the pixel size.
Image Mosaicking:
Image mosaicking is used when the area of interest cannot be contained in one satellite image. Mosaicking is used to bring together two separate pictures into one image. Mosaic pro is a program in ERDAS that makes mosaicking easy and does the job well.
Binary Change Detection:
Binary change detection is used to determine if two images have changed. This is useful when comparing an area from 1991 to the same area in 2011. In this section of the lab the model maker function was utilized to create an image from two images and determine what changed in that time. The new image was then overlaid on a whole image in ArcMap and the changes in the images were then clearly visible.
Results:
Subset Image
Pansharpened Image
Google Earth Sync View
Mosaicked Image
Binary Change Detection Overlay
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