Lab 7 - Photogrammetry

GOAL AND BACKGROUND

The goal of this lab was to explore photogrammetric tools for use on satellite images. Specifically, stereoscopy and orthorectification in Erdas Imagine are used.


METHODS

Stereoscopy was first used to generate some anaglyphs. The data used was of Eau Claire county. The first anaglyph was created using a DEM elevation image. The second anaglyph was created using a DSM image generated from LiDAR data. A section of this is shown in the results section.

The next part of the lab explored orthorectification. This was done with Erdas Imagine Lecia Photogrammetric Suite (LPS), which is a tool with a variety of applications, one of which is orthorectification. The study area for this part was Palm Springs, California.

First, a project was created within the tool and the first image was brought in. This image was then assigned 11 control points that matched to a reference image. Control points were chosen based on easy to identify features with edges, such as intersections. Once the control points were taken, the second image was brought in. Features on the image were then matched to control points previously taken. A triangulation tool was then run along with a resampling tool, so the images would match up well with the same spatial resolution. The final images were then output and checked.


RESULTS

Shown below is the anaglyph generated from the DTM, which was much more successful than the anaglyph generated from the DEM. You will need stereoscopic (blue and red) glasses to view it correctly.

In the orthorectification process, the control points between the two images is shown below.

The final output is shown below, along with a larger-scale view of the border of the two images. The border is difficult to see, which means the orthorectification process was successful. It is slightly visible running at a diagonal through the center of the 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.