Lab 8: Vector Analysis (and Building Models)

 

Part I: Vector Analysis

 

In this exercise you will be working on your own without a tutorial. You will explore the spatial distribution of salmon in the Hoh River watershed on the western Olympic Peninsula of Washington state. You will be using some of the basic vector analysis tools (queries, buffer, intersect, union, etc.) to produce maps that provide answers to questions about the salmon distributions. Read all the material carefully and pay attention to the hints.

Download the data for the lab (Lab8.zip) to a drive you have access to, then right click on the file, select Extract All, and follow the prompts for the extraction wizard. You will have the following layers:

 

Study Area Boundary

Land_Ownership

Roads for Clallam County

Roads for Jefferson County

WesternWA_LULC (Land Use/Land Cover)

 

You also have datasets showing distributions of four different species of salmon (Chum, Coho, Chinook, and Sockeye) along watercourses. Although they look like lines, each of these datasets is a five-foot buffer around a section of the watercourse, so they are polygon layers. When you view long narrow polygons such as these salmon distributions at the watershed scale, all you see is the outline and not the fill color for the polygon. If you want to change the symbology of the datasets or any subsequent results, change the outline color and/or its width.

 

Perform the following tasks and answer the questions found in step 2, 4, 6, and 9. Print the maps described in steps 7, 10, and 12.

 

 

  1. Open an empty map in ArcMap and add all the datasets. First you will need to prepare your datasets for analysis. Use the Merge tool (found in the Data Management Toolbox under General) to create one layer from the two separate road layers. Next, clip (found in the Analysis Toolbox under Extract) ALL overlapping datasets to the study area boundary.
  2. Now explore the salmon distribution datasets. Which of the salmon species has the most extensive distribution? Which has the least?
  3. When a new shapefile is created in an overlay process (such as using the clip tool), areas are not automatically updated. You can update them by using the Calculate Areas tool (script) in the Spatial Statistics toolbox under Utilities. The result is shown in a new field called F_AREA.
  4. Update the WesternWA_LULC dataset that you clipped to the study area. What is the sum of the updated areas? What was the sum before you updated the areas? Explain why they are different. Note that if you use topological vector data (e.g. coverages), areas and lengths are automatically updated.
  5. Now find the water courses where one can find all four salmon species present; in other words, where their ranges overlap (Hint: use the Intersect tool). We will call this result Areas of High Diversity. Then create a dataset that shows all the watercourses where one can find any salmon species (Hint: use the Union tool). We will call this result Combined Range.
  6. List how many polygons were created in the Intersect and Union operations and how many you started with. You could reduce the number of polygons by using the Dissolve tool before you started overlaying the datasets. If you were to do this, which field would you choose for the dissolve?
  7. Make (and print) a map showing both the Areas of High Diversity and the Combined Range. Be sure to include a title and a legend.
  8. Now you want to find which sections of the salmon ranges are most at risk because they are adjacent to logged areas, developed areas, or roads. In the WesternWA_LULC layer, the field PRIM provides land use/land cover codes:  the 200’s are developed areas, the 300’s are agriculture, and the 610’s are logged areas. Using the Combined Range result from Step 5, find the salmon ranges that are within 300 feet of a logged area or developed area (Hint: use Select by Attributes, Export, Buffer, and Intersect). Then find salmon ranges that are within 300 feet of a road (Hint: use Buffer and Intersect).
  9. A Select by Location query might seem like a good option for step 8, but it will NOT yield an accurate answer. Why not?
  10. Make and print a map that shows all the at-risk salmon ranges compared to the combined range. Be sure to include a title and a legend.
  11. Lastly, find out what level of protection exists for salmon in the study area. Using the Land Ownership layer, consider those areas in Olympic National Park to be the highest level of protection, Olympic National Forest, Native American Reservations, and Spokane District to be the next best, and private land to offer the least protection (in the Land Ownership layer, if the field AGENCY_NM is blank, that means the land is private).
  12. Make (and print) a map showing this ordinal ranking of protection as well as the at-risk salmon ranges, the Areas of High Diversity, and the Combined Range. Be sure to include a title and a legend.

 

Part II: Building Models (extra credit)

 

Do the tutorial exercises in Chapter 20 of Getting to Know ArcGIS Desktop.

 

Deliverables

 

Answer the following questions and produce the following outputs.

 

  1. What is a model?
  2. What are the three elements of a process within a model?
  3. List three benefits of creating a model.
  4. How do you know when a process has been run?
  5. At the end of exercise 20a, print the model.
  6. At the end of exercise 20b, print the model.
  7. At the end of exercise 20c, print the model.