Lab 4 - Remote Sensing

Goal

 The main goal of this lab is to give students a new set of skills that will help them with image processing, enhancing images for visual interpretation, be in a position to delineate any study area or AOI from sets of larger satellite image scene, and many other different skills that will help each student learn more about remote sensing. After this lab is complete each student should be able to complete each of these skills and apply them to different projects as well as real life situations in the future. 

Methodology/Results

To be able to complete this lab correctly we had to apply ourselves to different sets of skills regarding Erdas Imagine that we have never used before. The first step that we needed to complete involved "image subsetting of certain study areas" in order to properly subset the image we had to use a feature on Erdas called the Inquire Box. This feature would allow us to change a certain area of the map without doing anything else to the rest of the map. Below is an example of "Image Subsetting" and the use of an Inquire Box. 

Figure 1: Image Subsetting and Inquire Box

As you can see there is only one little box of the entire map that has been changed from the rest of the map, and if you look closely you can see that the part of the map that is located inside the "Inquire Box" actually has a higher resolution than the rest of the map. This is because of the "Image Subsetting" that occurred recently which helped us better define a section of the map that we wanted to have a higher resolution than the rest of the map. 

The next step of the lab was to do basically the exact same thing but this time instead of using an inquire box to change a certain part of the map, we were asked to use a shapefile of the Eau Claire and Chippewa county. Instead of creating a more defined area this shapefile will help separate these counties from the remainder of the map. Below is figure 2 which represents the counties of Eau Claire and Chippewa being separated by a shapefile. 

Figure 2: Shapefile of Eau Claire and Chippewa Counties

The next step of the lab we had to use a few new tools that are included in Erdas Imagine, these tools include pan sharpen and a resolution merge, this of course meaning that we will have both images having the same resolution as one another. Pan sharpen helps us improve the resolution of certain images so than the images become more clear and defined. Another tool that was crucial in the completion of this lab was "Radiometric enhancement techniques" these of course did basically the same thing as pan sharpen but in a different way.

Another way that this lab helped us learn new things on Erdas Imagine is that the next step was for us to first add an image into Erdas, but the next step after that was for us to connect that image to "Google Earth." This of course helps us learn about new ways that we can interpret different images such as using image interpretation keys to determine what kind of features are around certain areas. Resampling was also a great deal in this lab, for resampling the goal was to change the pixel size of the same image and see if it actually changed from the original image and if so how it changed. The conclusion that we came to was that just changing the pixel size of the image was not enough to change the resolution of the image, which means that the actual image didn't change.

After resampling we moved onto "Image Mosaicking" which we would use when a specific study area is larger than the spatial extent of an image scene that was captured by a single satellite. The goal of image mosaicking is to display two images at once while having a smooth color transition between the two especially at the borders of the two images. Below is figure 3 which is the original image of the two images that were used before any work was done to them. 

Figure 3: Image before Mosaic Pro

The next step was to use "Mosaic Pro" to help make a more smooth transition between the two images, so than it looks like one large image because of how smooth the color transition between borders is. In order to do this we needed to put in the two images in question into "Mosaic Pro" and change certain things so than the transition between images was smooth and barley if not noticeable at all. Below is figure 4 which contains the image after "Mosaic Pro" was used. 

Figure 4: Image after Mosaic Pro

As you can see the image has a much smoother transition between one another, you can barely see where one images border ends and the other begins. The final step of this lab has to do with Binary change detection or image differencing. In order to do this we had to use a few different skills that we had recently learned just for this lab, for instance we had to display a histogram of the metadata of two images and through out this final step we had to do multiple calculations so than we could create our final product which in turn helps us in the long run of the lab. Below is the histogram that we were asked to create of the original image that was used in this final part. 

Figure 5: Image Differencing Histogram

The last part of the lab had us use this tool in Erdas called "Model Maker" this is basically a tool that would let us use different images in an equation and a function to help us create a new map all by itself. We used this tool multiple times to create different maps, one of which helped us see the progress of an image and how it developed over 20 years with new buildings and features like that. Overall, this was a very helpful lab and taught me a lot about all the different things that Erdas Imagery can do and will continue to help me learn new things on the way.