Part 4—ANALYZE Geographic Information
Step 1 – Create a Data Legend
So why go to all that trouble just to plot points on a map?
Each of the geographic points on your map is linked to the full record of the data you collected. You'll be able to examine your data through the map interface, to help you identify geographic patterns.
- Double-click the icon to the left of your local_data file name in the Layer List to change its appearance.
- In the Shape tab, Choose Shape by... "Uniform" and select a circular shape.
- Click the Size tab and Choose Size by... "Uniform."
- For easy viewing, select Medium Size Range and move the sliding Size up to 60% or 70%.
- Click the Color tab. Choose Color by... "surftemp" and choose a colorscheme that suggests temperature. Click Apply and Close this window.
- The color of each point should now indicate the temperature measured at that site. What relationship do you notice, if any, between temperature and type of ground cover?
- Select the Pointer tool and click on points, one-by-one, and notice that an arrow above the legend at the bottom will point to the exact temperature measured at each point clicked.
Step 2 – View Tables and Sort Your Data
- To view and compare data not easily revealed by the map layers, click on the Show Table of the Selected Layer icon above the Layer List.
- Click on surftemp and the data will be sorted by ascending or descending surface temperature. Sorting data in this way is often helpful for finding the lowest and highest values in a field or looking for relationships between fields. For instance, notice that sorting this table by surface temperature causes the various forms of land cover to group together. Click image for larger view.
Step 3 – Create a Selection
Why would you create a selection? Sometimes it is helpful to select a subset of the data for easy analysis, especially if you have a large number of records.
- Switch to Analyze mode.
- On the left, choose Select by Value. On the right, Select Records from: "local_data" Whose "surftemp" Is Less Than "20." Change the result name to "cool areas" and click OK.
- It may be useful to make selections of warm v. cool points, or selections by type of ground cover.
- In Analyze mode, choose Select by Value. On the right, Select Records from: "local_data" Whose "lndcvr" Matches One Of The Values Checked Below: Check the boxes next to all natural surfaces, including bushes, dirt, grass and water. Change the result name to "natural surfaces" and click OK.
- Repeat step one, this time checking only boxes next to all urban surfaces, including blacktop, concrete and pavement. Change the result name to "urban surfaces" and click OK.
- In the Visualize mode, choose an appropriate Highlight Mode to view your selections for analysis. By choosing Highlight Mode: "Hide Unselected" you will see just the subset of selected points on the map.
- Highlight the selection "cool areas" and click on the Table icon. This will allow you will see a smaller table of just this subset of data.
Step 4 – View Your Links
- Under the local_data file name in the Layer List, select All (highlighting off).
- Select the Link tool. Flags will appear at any points where you linked images or other files earlier in the lesson. At each point that has a flag, click the base of the flag and then select the file you wish to access. Multiple links can be made to each point if multiple link fields are added in the Edit mode. In this lab, it makes sense to link images of ground cover at each location. Attaching links to a GIS project helps both to organize and communicate information about specific locations.
Step 5 – Create a My World Project Tour
- Click on Settings... in the Project menu.
- In the window that opens, check the box next to Enable Project Tour.
- In the box at the bottom of this window, type information about your project according to the guidelines provided by your teacher in between the two html "body" tags.
Step 6 – Save Your GIS Project
- To save your project, select Save Project As... from the File menu.
- There are different ways to save your project, but a nice way to keep everything in one place is to check Compress into a Single File.
- If you created links, make sure that you also check the box next to Include Linked Local Files.
- Leave the Include Remote Files box unchecked.