Photogrammetry

Introduction:

The goal of this lab was to teach the student how to perform key photogrammetric tasks on different aerial photographs and satellite images. The student will learn how to calculate photographic scales, measure area and perimeter of features as well as calculating relief displacement. The last task of this lab is to introduce stereoscopy as well as perform orthorectification

Methods:

The first section of the lab had the student finding the scale of different photographs. Data was provided and the student had to use formulas to find the scale for two different aerial photographs. The second task was measuring perimeters and areas of different polygon features within ERDAS Imagine. The third task was calculating the relief displacement from an object height. The student had to find the radial distance as well find its real world height by measuring the height in the photograph. The student then had to perform conversions in order to used their measured data within the provided equations. 

The second part of the lab introduced the student to Stereoscopy. The specific area being analyzed was the city of Eau Claire, WI. After performing stereoscopy on the images, polaroid glasses needed to be used in order to see the results of the analysis. The images produced allowed for the student to see the different elevation changes in levels, rather than gradual changes. 

The third part of the lab involved orthorectification. There were many tasks for the student to complete in this section of the lab. Some tasks included collecting GCPs, performing automatic tie point collection, triangulating images, selecting a horizontal reference source and orthorectifing images. 

Results:

All of the processes performed in the third part of the lab were intertwined. They all compiled on each other in order to come to an end result. The figure below (Figure 1) show the results of all the placed GCPs as well as the generated tie points. 

Figure 1 shows the different GCPs and tie points for both images.

The second image (Figure 2) is the results of all the processes combined together. The two images that were orthorectified were overlaid with each other to produce one image. 

Figure 2 is the result of the two orthorectified images being overlaid. 

Sources:

United States Department of Agriculture, 2005.

United States Department of Agriculture Natural Resources Convservation Service, 2010.

Erdas Imagine