Lab 1: Raster Modelling in ArcGIS
This lab teaches you how to do raster spatial
analysis including map algebra. If the data are not on the
hard drive of the computer you are working on then you will need to download
them from our server. Go to the I:\students\instructors\emch\ArcTutor
directory and download the file named Spatial.zip. You will need to
Part I: Introduction to ArcGIS Spatial Analyst
You will use the Acrobat book called
Using ArcGIS Spatial Analyst
to do the exercise. Read Chapter 1 and do the Quickstart Tutorial
exercises in Chapter 2. Answer the following questions
and produce the following outputs. Return them to the instructor by the due date.
Labs should be typed, include your name and lab number, be well organized, and be stapled together.
Part II: Understanding Rasters and Analysis in ArcGIS
- There are many different choices for defining the analysis
extent in Spatial Analyst. Explain the analysis extent and describe
the options that you may use in ArcGIS to select the extent.
- Explain the different options available in ArcGIS to select a cell size for analysis outputs.
- What does the value field represent in the ArcGIS raster format?
(Hint: The two main types of data are represented differently with the value field)
- How do you reclassify nominal data such as landuse?
- What is cost weighted distance as opposed to Euclidean distance?
- Calculating the shortest cost path requires a cost distance raster layer, a cost direction raster layer (which defines the direction
of the lowest cost), and a destination file. This type of calculation
is called the least cost pathway. What does the resulting map really
mean? The least cost of what?
- At the end of Exercise 3 of the tutorial, export the final map
to a JPG and paste it into your lab MS Word document.
Read Chapter 4, 5, and 6 and answer the following questions.
Part III: Spatial Analysis in ArcGIS
- What is a region?
- Explain the concept of NoData.
- Before specifying a cell size you should take into account, the
resolution of the input data, the desired response time, and the application
and analysis to be performed. Explain each by giving an example.
- How do you assign attributes to a raster data set for catagorical
data and how does it differ with assigning attributes to continous data
- Spatial analyst can use either features or grids as inputs. When
a feature is used the software first rasterizes the feature and then performs
the operation. Give an example of each.
- When creating rasters from existing maps you must consider age,
accuracy, resolution, and compatability. Explain each of these concepts.
- Explain the difference between local, focal, zonal, global, and
Read Chapter 7, do the following tasks, and answer the following questions.
Log onto the
Oregon Geospatial Data Clearinghouse web site
and click on the Data by... Alphabetical Listing link. There are six columns in the table.
The E00 file is an ArcInfo interchange file (also called an ArcInfo Export file).
ShapeFile is an ArcView shapefile. Image is a preview image. Metadata is descriptive
information about the data. Not all data are available in both Shapefile and
E00 formats. Click on the E00 file for County Boundaries-Oregon (blm) file size.
Save it to disk in a location that you have access to.
Navigate to the file using Window's Explorer. Double click on the zip
file to unzip (extract) its contents. Then
download and unzip the following E00 files: Cities (USGS), Highways (USGS), Population (USGS), State Boundary (USGS), and
Vegetation/Species(Idaho F&W GAP vegetation, 1:250,000). After you unzip them
all then you can convert the E00 files into ArcInfo coverages.
To avoid confusion, it’s best to save these coverages in a new folder, separate from the files that you unzipped.
Open ArcToolbox, choose >Conversion Tools >Import to Coverage >Import from Interchange
file and then choose the first E00 file and an output name and location for
the coverage. Import each of the other files into ArcInfo coverages in the same way.
Start ArcMap and open a new empty view. Click the button
and add all of the ArcInfo coverages to your map by double-clicking on them individually and
choosing a feature class. For each coverage, you will specify the feature class that you want
to add to the map (coverages and geodatabases may have multiple feature classes while shape files
only have one type of feature per data set). The feature classes used by this exercise are:
Highways – arc, State Boundary – polygon, Counties – polygon, Population – point, Vegetation/Species – polygon, Cities – point.
Once all of the coverages are added to the map, right-click on the data frame properties at the top of the table of contents (named 'layers').
Click on the general tab and choose feet for the map and display units.
The projection information was imported with the coverage.
If you would have brought in a Shapefile then you would have had to
put this information in manually. The projection parameters are as follows:
Projection: Lambert Conformal Conic
Scale Factor: 1.0
Now set the Spatial Analysis options as follows:
Working directory: to one you have write access
Analysis Mask: use the Oregon State Outline file
Cell Size: 5000
You will now do several spatial analyses using the Spatial Analyst menu
commands. Make sure that the maps that you create have the SA# as part
of their title.
SA #1: Calculating Distance from Highways using the Euclidean Distance
Under the Spatial Analyst toolbar choose Distance, Straight Line and use
the highway coverage as the Distance to file.
Make a map of the result, add your name using a text box, and print
SA #2: Allocating Space using the Allocation Tool
Under the Spatial Analyst toolbar choose Distance, Allocation and use
Cities as the Assign to coverage.
Make a map of the result and print it with your name. Using
a text box describe the map in your own words directly on the map.
SA #3: Calculating Population Density using Density Functions
Under the Spatial Analyst toolbar choose Density, Density Type-simple,
Search Radius-100,000, Population Field-pop85.
Make a map of the result and print it with your name. Using
a text box describe what the units mean, directly on the map.
SA #4: Highway Accessibility by County Using Zonal Statistics
Under the Spatial Analyst toolbar choose Zonal Statistics, Zone Dataset-county
coverage, Zone Field-name, Chart Statistics-checked, Join Output Table
to Zone Layer-checked, Value Raster-use the result of SA#1 (Euclidean Distance
Surface From Highways)..
Then make a choropleth map using the Oregon County vector coverage
by using the zone mean statistic as the attribute. Using a text box
describe what the units mean, directly on the map.
SA #5: Rasterize a Vector File and Use it To Calculate Vegetation Diversity
Using a Neighborhood Statistic
Under the Spatial Analyst toolbar choose Convert, Features to Raster,
Input Features-Vegetation, Field- com_code. Under the Spatial Analyst
toolbar choose Neighborhood Statistics, Input Data- state vegetation raster,
Field- value, Statistic Type- variety, Neighborhood-rectangle (3x3). Then
make a map of the result. Using a text box, describe what the units
mean and why they have the range they do.
SA #6: Reclassify the Raster Vegetation Variety Neighborhood Surface
into Two Classes
Under the Spatial Analyst toolbar choose Reclassify, Input raster-
variety surface created in SA#5, Reclass Field- value, Method- equal interval,
Classes-2. Then make a map of the result.
SA #7: Using the Raster Calculator to Change Cell Values (to m from
feet), the Reclassification Tool to Reduce the Number of Classes, and
Under the Spatial Analyst toolbar choose Raster Calculator, double
click on the distance to highways raster created in SA#1, click on /, type
3.28, and click Evalutate. Then reclassify the result into 3 natural
breaks classes. Then convert the raster to a vector by choosing Convert,
Raster to Features from the Spatial Analyst menu (it doesn’t matter which field you use for this operation).
Then make a map of the result that includes a legend.
Part IV: Implementing Map Algebra Commands Within
the Raster Calculator
First read Appendix A of the tutorial book. The Spatial Analyst
Raster Calculator allows you to use all ArcInfo MapAlgebra GRID commands
and functions. Learning map algebra is like learning any language.
Once you know the syntax then you need to increase your vocabulary.
In this exercise you will implement one map algebra function using
the Raster Calculator. First rasterize
the highway vector coverage that you downloaded in Part III and call it HW.
Then choose Programs, ArcGIS, ArcInfo Workstation, ArcDoc, Contents,
Command Reference for ArcInfo Extensions, GRID, Alphabetical List of Grid
Functions. This is a comprehensive help system for ArcInfo MapAlgebra.
Read the help topic for Thin. Then open the raster calculator
and type: thin([HW]) and then click evaluate. If it works then you have
implemented your first MapAlgebra command that is not available through buttons
or menu commands within Spatial Analyst. Make a map of the result and
include a description of the result in a text box as well as your name.
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