In this lab we converted images with no spatial reference system to georeferenced systems that could be used in ArcMap. Georeferencing was done using both a control image and control points for images collected in lab as well as a historical aerial photo from 1953.
Task 1: Georeferencing a scanned historical image
For the first part of the lab, we took an image which was flown in 1953 and referenced it using a control image from 2002. The transformation method used was protective, which warps the image. It is useful for oblique imagery, which is the type of image taken in 1953. My criteria for selecting a transformation method was the root mean square (RMS) error, which was lowest with this method. Referencing the image was a difficult task due to the time difference between imagery dates. Very few landmarks were available to be used as control points.
Task 2: Georeference USU Quad using existing imagery
The image georeferenced in this task was captured in lab using a blimp flying over the quad. I selected the picture which I thought had the best spatial coverage and used an affine transformation once control points were selected. An affine transformation shifts, scales and rotates a image. I felt that it did the best job in showing the image in comparison to the control imagery. My overall RMS error was 1.62 for Task 2.
Task 3: Georeference USU quad using control points
For final lab task, an image was referenced using control points collected during lab at the same time the blimp was capturing aerial photos. I used a projective transformation, hoping that it would warp the image to create a more accurate product. I was comfortable using a warp here due to the large number of control points for a fairly small area. The total RMS error was 0.29 in Task 3.
References
Joe Wheaton & Shannon Belmont Lab 09 - Blimp & Georeferencing. 2015. gis.joewheaton.org. Web. 25 March 2015. http://gis.joewheaton.org/assignments/labs/lab10blimp
Joe Wheaton & Shannon Belmont Lab 09 - Blimp & Georeferencing - Task 1 - Georeferencing a Scanned Historical Image. 2015. gis.joewheaton.org. Web. 25 March 2015. http://gis.joewheaton.org/assignments/labs/lab10blimp/task-1-georeferencing-a-scanned-historical-image
Fundamentals of georeferencing a raster dataset. 2015. resources.arcgis.com. Web 25 March 2015. http://resources.arcgis.com/en/help/main/10.1/index.html#//009t000000mn000000