Due: Beginning of next weeks' lab (Please note--due at the beginning of the lab time. Labs handed in during your lab will be marked late by your TA.)

Marks: 41

Background

Four types of film have traditionally been used in aerial photography: panchromatic (black and white), which you used in Lab 1, black and white infrared, colour, and colour infrared. (Here is an overview of the benefits of Kodak's IR film, while here Kodak describes the specifications of the film.)

Colour film offers certain advantages over conventional panchromatic photography; in particular, hue and saturation (chroma) help photo interpreters in the identification of surface features. While trained photo interpreters can distinguish between 15 to 30 shades of gray in a panchromatic photo, they can distinguish between 100's of hues on colour photographs. Also, for novice photo interpreters, colour greatly benefits when assigning meaning to the features on the ground, as the images appear more natural.

However, colour film is not good at differentiating between similar natural colours, such as the various greens found in vegetation. Colour infrared (Colour IR) film, which, along with recording some wavelengths in the visible spectrum, captures the longer wavelengths adjacent to the reds of the visible spectrum, and thereby displays reflected infrared energy. As you should know from the lectures, plants reflect highly in the near IR wavelengths, and different species' reflectances differ. Colour IR film was developed in WWII to aid in the identification of objects camouflaged in order to appear as natural foliage. Today this spectral region (IR) is primarily used by remote sensors to aid in differentiating vegetation types, and in identifying plants under stress (e.g., from a lack of water or suffering from a disease), and in the identification of water features.

Each type of film (or representation) has advantages and disadvantages, characteristics that are documented in your text (Chapter 9.3). As well, reviewing the material in Chapter 7 (Visual Image Interpretation) might be helpful. From the Remote Sensing Tutorial, the following sections are relevant: Elements of Aerial Photography, The Photographic Process, and Some Elements of Photogrammetry.

Assignment

In this lab you will be working with 3 sets of aerial photos from an area near Fort St. John, BC:

1) A37445: 108/109, which are stereo colour photos from 1977 and
2) A37446IR: 108/109, which are Infrared photos from the same time.
3) BCC05129 - 50 and - 51, which are colour photos of the area from 2005 (used in the last questions of the lab).

We have made colour copies of the originals so the images may appear a little fuzzy under magnification. Others need to use these copies as well, so please do not write or mark the photos in any way.

Obtain set 1) and 2), the 1977 Colour and Colour IR photos of Fort St. John, BC. You will also need to use the stereoscope for this exercise.

1. Compare the following features on the Colour and Colour IR photos, and comment on the differences you see between them. Briefly note any differences and describe why they might occur. (4)
   1. vegetation
   2. roads
   3. water
   4. bare, unvegetated ground
      
      
2. Vegetation identification ('vegetation' includes forests, agricultural crops, shrubs, etc.)
   a) Although it is difficult to clearly identify individual tree species at this scale, you should be able to differentiate between categories of trees (coniferous (e.g.) and deciduous (e.g.)) with the magnification of the stereoscopes. Try to determine the category of tree in the river valley bottom, and that in the uplands and plateau. (2) (Hint: Take a look using Google Earth (kmz), if you have Layer Photos turned on, you should be able to find some photos of the river valley.)
   b) Which photo set is better for distinguishing between different types of vegetation cover? What are some of the main criteria that makes one better than the other? (2)
   
   
3. What appear to be some of the main types of agricultural activities in the region? Use the interpretive key here but keep in mind that not all potential activities are listed. Use clues such as field size, the presence of animals and building type to aid in your interpretation. (4)
   
   
4. List the major commercial/business activities shown in the photos and give a brief explanation as to the criteria you used in your determination. Include the entire area shown in both photos, not just the area encompasses by the stereo image. (5)
   
   
5. Answer the following in reference to the large river shown in the photos. Arrange the photos so that the photo numbers are on the bottom.
   1. What is the name of the river? (1)
   2. What direction is the river flowing? (1)
   3. Are the islands in the river stable over time (years to decades)? What evidence is there to support your answer? (3)
   4. Is there evidence of erosion along the steep slopes adjacent to the river? What evidence is there to support your answer (that there has been / has not been any erosion in that area)? (2)
      
      
6. Comment on the difference in the colour of the water in the two sets of 1977 photos. What do the colours indicate (why is one blue, the other brown)? (2)
   
   
7. Briefly describe how using the stereoscope can aid you in feature identification. It may be useful to refer to some of the features you identified in your answers to the questions above. (2)
   
   
8. What spectral bands does Colour IR film use? (Provide the name and the spectral wavelengths [µm].) (1)
   
   
9. Search the UBC library on-line journals or use Google scholar to find an article where Colour IR film was used to help detect information about vegetation. Cite the paper (bibliographic reference using the citation style identified in Lab 1) and write a paragraph summarizing how the Colour IR film was used. (5)

Obtain the 2005 colour photos:

10. Compare the 2005 photos to the 1977 photos. After examining the area that appears in both sets of photos, discuss the changes that have taken place to the agricultural and urban features that you identified in the 1977 photos (in your answers to questions 3 and 4). (2)
    
    
11. Bring up Google Earth and zoom to the Fort St. John area (kmz).
    a) For the Google Earth imagery of Fort St. John, what is the source of the imagery (zoom into the urban area before looking for the attribution)? Estimate the resolution of the imagery (Hint). (2)
    b) Describe differences between the Google image and the airphotos. Is there more information to be gained from Google Earth? (2)