Remote Sensing Lab 7

Ethan Nauman

12/2/14

The goal of this lab was to develop our skills in performing key photogrammetric tasks on aerial photos and satellite images. This lab was specifically detailed to train us in the mathematical calculations of photographic scales, measurement of areas and perimeters, and calculating relief displacement. By the end of this lab I was able to perform diverse photogrammetric tasks. 

Part 1: Scales, measurements and relief displacement

Data for this portion of the lab was found in our Lab 7 folder. The first two questions of this lab dealt with figuring out the scales for two different maps. We were given the distance in feet from two points on the map and had to find the distance using a ruler on the maps. After finding the distances we then had to perform calculations that would allow us to find the scales of the maps. 

This is the photo we used for calculating the scales.

Section 2: Measurement of areas of features on aerial photographs.

This section of the lab was performed in the Erdas Imagine. For the first part we displayed the Eau Claire-west-southeast picture from our lab 7 folder. We then were asked to find the area of the lagoon that was marked on the map. We used the polygon measuring tool to perform this action. This would allow me to single click points around the lagoon, then would tell me the final area of the lagoon. I could also change the measurement tools to whatever the question was asking for, acres, hectares, etc. After finding the area of the lagoon, we were then asked to find the perimeter of the lagoon. Using the same tool concepts, the only change was instead of using the polygon tool, we used the polyline tool. This allowed for the tool to find the perimeter of the lagoon rather than the area. We could also change measurements of the tool to whatever the question was asking for. Below is a picture of the lagoon labeled with an 'X' that we had to find the perimeter and area of. 

Section 3: Calculating relief displacement from object height.

We used the Jpeg of Eau Claire-west-southeast from our lab 7 folder for this section of the lab. We were asked to find the relief displacement of the smokestack labeled in the photo. We were given the height of the aerial camera above the datum, and the scale of the photo. Also we were given the principal point on the photo. 

Calculating the relief displacement took time and careful measurements to figure out the exact amount of relief displacement. 

Part 2: stereoscopy

For this part of the lab we needed a pair of polaroid glasses that would allow us to view our maps and would allow us to see elevation. We began in Erdas Imagine and brought in a photo of the city of Eau Claire at a 1 meter spatial resolution. I then brought in a second image into another view which was the dem of the city of Eau Claire. This photo was in a 10 meter spatial resolution. I used one form of GCPs to show a 3-dimensional perspective view of the city. From the main interface I clicked on the terrain tool bar which allowed me to select anaglyph. For the input DEM I used the EC-DEM, for the input image I used the EC-City image. I also increased the vertical exaggeration and saved the output image in my personal lab 7 folder. I accepted all other parameters and ran the program. The image that it gave me was not much different then the original image until I put on the glasses. The glasses allowed for me to see elevation changes throughout the image. 

Part 3: Orthorectification.

This part of the lab introduced me to the Lecia Photogrammetric Suite in the Erdas Imagine viewer. This is used in photogrammetry, orthorectification, and extraction of elevation. This part of this lab took awhile to get used to and complete, the tasks for this part were: create a new project, select a horizontal reference source, collect GCPs, add a second image to the file block, collect GCPs in the second image, perform automatic tie point collection, triangulate the images, orthorectify the images, view the orthoimages, and save the block file. The LPS tool was located under the toolbox function. Once the LPS project manager was open, it allowed me to change the parameters in the model setup. I changed it to a polynomial based push broom and the SPOT push broom. I also had to change the horizontal reference coordinate system. I used the UTM projection, the spheroid name was Clarke 1866, and the datum name was NAD27 (Conus). 

Section 2: Add imagery to the block and define sensor model. 

Now I brought in the first of two images into the block and had to accept the parameters. After accepting the parameters I had to activate the point measurement tool. I changed it to a classic point measurement tool and upon okaying it, it opened another viewer and brought in my image into three different panels. A regular view and two zoomed in views. In this view I checked the 'use viewer as reference' box and input my second spot pan image. Now I have the spot pan image on the right and the xs-ortho image on the left. 

The next step was to collect GCPs on the ortho image. After referencing the GCP in our lab I was able to find where the first GCP went. My X and Y reference almost matched so I didn't have to change them. Next I had to collect the corresponding point on the block image, right image. I moved the inquire box on the full scale image then moved the zoomed inquire box to the exact area that I needed. This allowed me to collect the GCP for the block image. Once again my X and Y reference was almost identical. After collecting another GCP on both images I then activated the Automatic (x,y) Drive. This allowed me to collect the GCPs in rapid succession. I collected GCPs up to 10, the final two GCPs were on a different image. After the 10th GCP I then saved and reset the horizontal reference source. This allowed me to bring in the other image, NAPP-2m-ortho. 

I then collected the final two GCPs from the second image I input. After collecting the final GCP I saved again and now had to collect GCPs for elevation. I used the reset vertical reference source and used the plasm springs DEM. I right clicked on the Point # and selected all, then used the update Z values tool button. 

Section 4: Set type and usage, add a 2nd image to the block and collect the GCPs. In the cell array under 'Type', I changed all the points to full, and under the Usage cell I changed all the points to control. 

Now that I have finished the collection of reference points for the first images, I then moved to the second image, spot-panb. I uploaded the spot-panb image and referenced the GCPs off the first spot-pan. I used the point measurement tool which allowed me to locate the points in the first spot-pan on the second image. I collected all 12 of the GCPs on the second spot-panb image. After saving the points again I referenced my block image interface. This showed me where the points were located on the two images. 

Section 5: Automatic tie point collection, triangulation and ortho resample.

Finally I was at the last couples steps to allow me to orthorectify my images. I used the 'Automatic tie point generation properties tool. My images used was set to all available, my initial type button was set to exterior/header/GCP, under the distribution tab in the intended number of points/ image field I set to 40. I then ran the tool. An auto-tie summary is displayed allowing for me to see the accuracy of my GCPs, after looking at this summary I saved it and closed it. After completing all these steps I had all the control and tie points, the nest step was the triangulation process. I used the 'Edit Triangulation Properties tool. I changed the interations with relaxation from 1 to 3, under the point tab I changed the x,y, and z fields to 15. I then ran the triangulation process. After the function ran it gave me a report summary. 

After looking over the report summary and saving it, I exited out. This brought me back to the LPS interface. I now can create my orthorectified images. After running the orthorectifying process I then was able to view my two images. The images overlap each other but they blend very well into each other. The features blend very well together, if it wasn't for the borders on the image overlay, it would be difficult to tell that there is two different images. My final two images that are orthorectified appeared as this. 

I was very pleased how this process turned out for me. I am thinking about using this in my final term project. The only problem is that this was considered to be "the marathon lab" due to the fact that it takes sometime to collect all the GCPs and tie points. However, with that being said it was a good feeling after completing this lab.