Lab 7 Remote Sensing of the Environment

GEOG 338
Charlie Krueger
Lab 7: Remote sensing of the Environment

Goal and Background:
The main goal of the lab that was assigned was to improve on the skill of performing important corrections on aerial photos and satellite images. These images can have many issues when being viewed by researchers and by being able to correct these images leads to the improvement of data gathered from this research. This lab was created to strengthen and sharpen skills such as calculation of photographic scales, calculation relief displacement, and measuring the area and perimeter of objects in an images. The lab also brings in new information to the class about performing orthorectification on images taken by satellites and by the end the class will have the information to perform many different photo correcting tasks.

Methods:
The first part of this lab was focused on calculating scale of nearly vertical aerial photos which was covered in lecture and had been discussed prior to the lab. There were formulas that were need to solve each one of these problems plus the information that was given in the problem. On both of the problems a measurement on the computer screen had to be made to get info to solve the problem. This was a concern because of the fact that the screen was difficult to measure and could give different results if a different person were to measure it. In this same section the program ERDAS Imagine was used to find the perimeter and area of a lagoon taken for a satellite image. The program used a measurement tool and all that was done after that was carefully going around the edge and plotting point and then the answer was given after the whole lagoon had been surveyed.

The second part of this lab was stereoscopy which is the generation of a three dimensional image using an elevation model. The program that was used to create these 3D images was the ERDAS Image terrain tool Anaglyph which took the two images that were selected in the lab and ran a program over them creating the image. This was done twice in this section with the result from the second run program creating a very interesting 3D image. The 3D could only be seen while wearing blue and red lensed glasses or 3D glasses.

The last section of the lab was the orthorectification part which was the largest part of the lab and by far the most strenuous. This process takes two images that are close to each other in location but that do not fit together and runs programs so that it makes one smooth image. To begin with the toolbox button was selected and then Imagine Photogrammetry was selected and that brought up a whole new dialog box. The model setup was done by selecting polynomial based push broom and then SPOT Push broom. The coordinate system was then corrected was that the final images would line up with one and other in the same system. Next the images are added in the add frame icon, with this image on the screen the show and edit frame properties icon was selected which when looked and confirmed the image could then start to be edited. The Start point measurement tool was selected and the process of selecting ground control point began. In total 12 ground control points were selected between the reference image and the image trying to be corrected. The reference image was there to make sure that the positions of the ground control points were correct and the image would not be slanted in a strange way. After these points another reference image was added and another six ground control points were added. This second image was added to have another reference image and make the final image even more accurate. Next the reset vertical reference source icon was selected and this was allowed the Z value to be given to the images. The Z value would be the height in this image and would be given from the DEM palm_springs_dem.img. Finally, after a long process the Edit- Triangulation Properties icon was selected and there were many items changed in here because of the images specifics used in the program. The triangulation was run after this two images were selected to be made from this program and then these were brought to the viewer and held the end results.

Results:
Here is the image created from the Stereoscopy process. This image was created by a computer program that was given specific images that would create a 3D image. The process was simple because the lab laid out the specific details of how to create the image.

Stereoscopy Image

This second image is from the orthorectification process of the lab and it can be seen that there is a small black line that run in between the images. This goes away when the user zooms in using the Imagine program. This process was very detailed oriented and took a long process because of the selecting of the ground control points.

Orthorectification Image

Sources:
National Agriculture Imagery Program (NAIP) images are from United States Department of Agriculture, 2005.
Digital Elevation Model (DEM) for Eau Claire, WI is from United States Department of Agriculture Natural Resources Conservation Service, 2010.
Lidar-derived surface model (DSM) for sections of Eau Claire and Chippewa are from Eau Claire County and Chippewa County governments respectively.
Spot satellite images are from Erdas Imagine, 2009.
Digital elevation model (DEM) for Palm Spring, CA is from Erdas Imagine, 2009.
National Aerial Photography Program (NAPP) 2 meter images are from Erdas Imagine, 2009.