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Exercise 9: Spatial data analysis - Land use change Spatial data analysis is the ability analyze the spatial data based both on the attributes of specific fields as well as the spatial characteristics such as proximity, distance, intersection and area. It is when you begin to explore some of the spatial data analysis processes that they true value of GIS, spatial data and the tools available show their greatest potential. In this exercise you will use many tools to determine the amount of land that is modeled to be lost to urbanization. You will begin by intersection two layers, finding the area where these two layers overlap with each other. You will then dissolve your data based on fields in the attribute table. This will simplify your data, making it easier to work with. You will then use tools field calculator tools to calculate area. When completed, with your analysis, you will generate a report of your findings. You will be generating a lot of new and intermediate layers. Be particularly careful in naming layers to something you can comprehend as well as taking care with your file management. In this exercise you will: Extract regions within your county where land use change is modeled to occur Calculate the area of proposed land use change Create a report of your findings The Scenario You are the GIS lead on a research team investigating urban sprawl. You need to determine the land use change that will result if the predicted urban sprawl continues.

Exercise 9: Spatial data analysis - Land use change

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Page 1: Exercise 9: Spatial data analysis - Land use change

Exercise 9: Spatial data analysis - Land use changeSpatial data analysis is the ability analyze the spatial data based both on the attributes of specific fields as well as the spatial characteristics such as proximity, distance, intersection and area. It is when you begin to explore some of the spatial data analysis processes that they true value of GIS, spatial data and the tools available show their greatest potential.

In this exercise you will use many tools to determine the amount of land that is modeled to be lost to urbanization. You will begin by intersection two layers, finding the area where these two layers overlap with each other. You will then dissolve your data based on fields in the attribute table. This will simplify your data, making it easier to work with. You will then use tools field calculator tools to calculate area. When completed, with your analysis, you will generate a report of your findings.

You will be generating a lot of new and intermediate layers. Be particularly careful in naming layers to something you can comprehend as well as taking care with your file management.

In this exercise you will: Extract regions within your county where land use change is modeled to occur Calculate the area of proposed land use change Create a report of your findings

The ScenarioYou are the GIS lead on a research team investigating urban sprawl. You need to determine the land use change that will result if the predicted urban sprawl continues.

Page 2: Exercise 9: Spatial data analysis - Land use change

Exercise 9: Spatial data analysis - Land use change

Page 2Exploring the Fundamentals of GIS by Scott Crosier

Joining two ajoining feature classes (Merge)

For this exercise, add the following data to a new ArcMap document. The sources for this information are included in Appendix B: Data sources.

• County outline of your county.

• Land use / land Cover dataset(s) for your county

• Urban growth projection for 2020

• Urban growth projection for 2050

At times, you may find that data you want is not available as one complete feature class but as several features classes next to one another. This os often the case when dealing with data developed based on the USGS 1:24,000 map extent or other map extents. When this is the case, you may need to ‘glue ‘ the two feature classes together. This process is referred to as a merge.

This ArcToolbox function is outlined below using ArcMap, although the same tool could be run through ArcCatalog.

The merge process is only used for Vector data. When working with Raster data, use the Mosaic tool.

1. Be sure that the two layers you wish to merge are added to your map document.

2. Open ArcToolbox via ArcMap.

3. Navigate to the Data management tools /General / Merge tool and open the tool.

Some counties, such as San Joaquin county shown above, require more than one land use layer to cover the entire extent of the county.

Page 3: Exercise 9: Spatial data analysis - Land use change

Exercise 9: Spatial data analysis - Land use change

Page 3Exploring the Fundamentals of GIS by Scott Crosier

4. On the Input dataset drop down menu, click the first dataset you wish to merge.

This will add that dataset to the Input Dataset list.

5. Repeat step 4 for the next dataset(s) you wish to merge.

6. Specify a name and file path for the merged dataset you are creating.

7. Click OK.

This will begin the ArcToolbox processing.

8. Add the new feature class to your map document.

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Page 4: Exercise 9: Spatial data analysis - Land use change

Exercise 9: Spatial data analysis - Land use change

Page 4Exploring the Fundamentals of GIS by Scott Crosier

Spatially joining two layers (Intersect)

When intersecting two layers, you are joining the spatial area as well as the attribute tables for two different layers.

In this task you will intersect the land use layer with the proposed urbanized area layer.

In so doing, you will create a feature class that specifies the current land use of all of the area that is proposed to become urbanized.

1. Navigate to the Analysis tools / Overlay / Intersect tool and open the tool.

2. From the Input Features drop down menu, select the land use layer for your county.

3. Repeat step 2, adding the Urban 2020 layer.

4. Specify a name and path name for your resulting feature class.

5. Leave all other values at their default settings and Click OK.

The resulting feature class consists of a layer where all of the areas that are modeled to be urbanized in 2020 are showing

6. Add the new feature class to your ArcMap document.

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Page 5: Exercise 9: Spatial data analysis - Land use change

Exercise 9: Spatial data analysis - Land use change

Page 5Exploring the Fundamentals of GIS by Scott Crosier

Joining all features with the same attribute (Dissolve)

The resulting layer from the previous task contains many features with the same land use value. Although this might be helpful in some applications, for this exercise, you will be focusing on the total areas of current non-urban land use loss due to urbanization. You will dissolve the layer based on the land use value, creating multi-part polygons of each land use type.

The layer you generated in the previous task has an extent beyond your county boundary.

1. Clip the data based on the outline of your property boundary based on the task outlined in Exercise 5: Clip data based on the outline of another layer (cookie cutter)

2. Navigate to the Data management tools /Generalization / Dissolve tool and open the tool.

3. From the Input Features drop down menu, select the 2020 land use layer for your county you generated in step 1 above.

4. Specify a name and path name for your resulting feature class.

5. In the Dissolve Fields pane, check the check boxes next to LUCODE and LANDUSE.

6. Leave all other values at their default settings and Click OK.

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Page 6: Exercise 9: Spatial data analysis - Land use change

Exercise 9: Spatial data analysis - Land use change

Page 6Exploring the Fundamentals of GIS by Scott Crosier

8. Add the new feature class to your ArcMap document.

9. Open the attribute table.

On the attribute table, you will notice that the number of features have been greatly reduced. Each features consists of a multi-part polygon for all of the features with the same LUCODE value.

Leave the attribute table open for the next exercise.

The resulting attribute table. The data has been dis-solved, leaving only one, multi-part feature for each land use code.

Page 7: Exercise 9: Spatial data analysis - Land use change

Exercise 9: Spatial data analysis - Land use change

Page 7Exploring the Fundamentals of GIS by Scott Crosier

Using the geometry calculator

In this task, you will calculate the areas for each of the features in the feature class.

Calculating geometry is not feasible when your data frame is using a geographic coordinate system. You must change the spatial reference of the data frame to a projected coordinate system, as outlined in step one below.

1. Change the coordinate system of the data frame based on the task outlined in Exercise 5: Assigning and changing the spatial reference of your data frame. Assign the data frame to the UTM coordinate system that corresponds to your county.

1. Add a field to the attribute table based on the task outlined in Exercise 6: Creating a new field. Set the name to ACRES, and the field type to Double.

2. Right click the ACRES field name and select Calculate Geometry.

A prompt will inform you that you are beginning to edit the table outside of an edit session and that any changes you make cannot be undone.

3. Click Yes to continue to the Calculate Geometry dialog box.

This will open the Calculate Geometry dialog box.

4. In the Property drop down menu, select Area.

5. In the Units drop down menu, select Area.

6. Click OK to calculate the area of each of the features in the feature class.

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Page 8: Exercise 9: Spatial data analysis - Land use change

Exercise 9: Spatial data analysis - Land use change

Page 8Exploring the Fundamentals of GIS by Scott Crosier

Creating a Land change layer

You will notice that in your land use feature class, you have features for those areas that are proposed to change, as well as those areas that are already urbanized. In this task, you will extract out the features that are proposed to change to create a layer consisting of only those changed areas. To do so, you will use similar steps as found in Exercise 6: Select by attribute, and Export selected features.

You may notice that all of the values between 11 and 17 are existing urbanized regions. You will select the areas have a value greater than 17 and extract those to a new layer.

1. Click Selection on the main menu and choose Select by Attributes.

This will open the Select by Attributes Dialog box.

2. In the Layer drop down menu, select the dissolved layer you created in the previous task.

3. In the methods drop down menu, leave the default value of Create a new Selection.

4. Double Click LUCODE in the fields dialog box.

5. Click the Greater than (>) button on the left side of the dialog box.

6. Click the Get Unique Values button to populate the field values pane.

7. Double click the value 17.

At this point, the formula pane should be populated with “LUCODE” > 17.

8. Click OK to select only those features whose LUCODE value is over 17.

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Page 9: Exercise 9: Spatial data analysis - Land use change

Exercise 9: Spatial data analysis - Land use change

Page 9Exploring the Fundamentals of GIS by Scott Crosier

9. In the table of contents, right click the layer name of the dissolved layer you created in the previous task.

10. Select Data / Export data.

This will open the Export data dialog box.

11. In the Export drop down menu, leave the default value of Selected Features.

12. Specify the file path and name of the new Shapefile you will create.

13. Leave all other values as default and click OK to export the selected features to a new shapefile.

14. When prompted, click Yes to add the exported data to the ArcMap document.

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Page 10: Exercise 9: Spatial data analysis - Land use change

Exercise 9: Spatial data analysis - Land use change

Page 10Exploring the Fundamentals of GIS by Scott Crosier

Developing a report

You have created a shapefile of all of the proposed land use change to take place by 2020. You now must present this information in a report. Your report should include the following information.

Data sources: You should include information on the source of data as well as any additional background information about that data, such as how it was created and so forth.

Data Analysis Process: Based on that data, you should include a description of the processing you did with that data. Outline the process you did throughout this exercise to the extent that another person with GIS skills and understanding could re-generate the same results.

Results: You should include your results using both a map as well as a data table. Export your map to a image type that can be imported into your document.

Data tables can be generated using the Reports option found on the Tools button on the main menu. Graphs can also be generated using the Graphs option found there as well.

Further Analysis: You may have other analysis that you plan on doing or that could be done on the same project. For example, you may plan on running the same analysis using the 2050 urbanized region data. This will give the reader an idea of what you also plan to do or what they could do to continue your research.

Want More?• Run the same analysis for land change to take place by 2050 and include that in your report.