Name:
Date:

1. While you were classifying the DEM, you may have noticed an unexpected pattern in the histogram of the data.  Go back and look at the histogram again.  The distribution of elevations is not what you would expect if the elevation had been directly measured for every pixel (as would be the case in, for example, SR-TM data).  Describe the pattern and explain why it is there.
 
 
 
 
 

2. DEMs and TINs are often referred to as "2 1/2-D" rather than "3-D."  Why do you think this is?  Hint: In a surface, how many z-values are there going to be for a given (x, y) coordinate?  In a system that requires a truly 3-D model, how many z-values are possible per (x, y)?
 
 
 
 
 

3. Upon visual inspection, what are the differences between sbdemtin and sbctin?  Consider: level of detail and information lost in the creation of each TIN.  Also use the identify tool and click around on the Santa Barbara Channel for both TINs.  Explain the elevation results for the ocean in both TINs and the reason for the differences between them.
 
 
 
 
 

4. Examine the histograms for your two TINs.  What are the unnatural patterns in each and what are the likely causes of them?
 
 
 
 
 

5. What kinds of geographic information would be most useful to you if you were seeking to mitigate the major problems you have discovered with the TINs above?  Especially consider: what would be the best source data to use for generating TINs?
 
 
 
 
 

6. At 8 p.m. on July 31st, 2000, a landslide occurred about 26 miles west of Santa Barbara (near the Tajiguas landfill).  "Hundreds of tons" of earth slid towards the beach, leaving "a 300 foot section of track hanging in midair."  Fortunately, sensors stopped two approaching freight trains, but an Amtrak train had passed over the tracks "just hours earlier."  (Van de Kamp, Santa Barbara News-Press, 2000)  It was a perfectly calm day in the middle of a dry summer. 
     Imagine that you have been hired by Union Pacific Railroad (www.uprr.com ) to try and use GIS to try and identify other areas where landslides are a possibility.  Obviously in real life, one would need specialist training or advice to adequately do such a job; but you should be able to lay out a general strategy for such an analysis (what data layers you would need and what kinds of analysis you would do).  Do so in one paragraph.  
  
  
  
  
  
  
  
  
  
  
 

Question #7 : What is your assessment of the viewshed?  Does it fit with what you can actually see from that point?  What would account for differences?
 
 
 
 
 
 
 
 

Question #8 : Describe the vegetation profile as you move along a straight line from Campus Point to the east edge of Lake Cachuma.  Make a list of the vegetation types in the order that the line crosses them, and give approximate elevation ranges for each of the vegetation types.

Note: There are several decent ways to do this.