Geography 281 Map Making with GIS Project Ten: Mapping and Spatial Analysis This project introduces three techniques that enable you to manipulate the spatial boundaries of geographic features: Clipping the geographic extent of one theme with the geographic extent of another. Dissolving two features by removing the boundary between them. Drawing buffer zones around features. Together, these spatial techniques help you modify your datasets to fit the needs of your mapping project. In addition, you will learn how to classify nominal data. Project Objectives: Create a Unique Values map. Use geoprocessing tools to create new data. Create a locator map. Optional- insert pictures into map layout The data needed for Project 10 is located in the \\geogsrv\data\geog281\proj10\data\project10.gdb Project 10 files: Description: Feature Type: calcoast feature class California Coastline line calif feature class California State Outline polygon eco feature class World Ecological Regions polygon The first part of the activity guides you through the steps you need to take when applying geoprocessing tools to your data. The second part of the activity lets you create a map using these geoprocessing techniques. After copying the data from the server to your local working directory, start ArcMap. Project 10 does NOT start with a map document file; you will need to create one. Create a map document file for Project 10 Name the file proj10.mxd Add the following feature classes to the Data View eco calif If necessary, change the drawing order so Calif draws on top of Eco. Working with the ArcToolbox ArcToolbox includes a number of spatial analysis tools that permit you to edit and modify your spatial datasets. Two of the most useful techniques are called Clip and Dissolve. The Clip tool enables you to eliminate portions of a layer that lie outside your study area. The Clip function overlays one polygon layer on top of the other and effectively deletes features or parts of features in the second layer that fall outside the geographic extent of the first layer. The Dissolve tool lets you generalize two attribute values into a single new value. If any polygons with the new value are adjacent to one another, dissolve lets you remove the now-unneeded common boundary between them.
Tool #1 Clip Before using the clip function, your view window should contain two layers with different underlying feature shapes and boundaries. The clip feature should have a smaller geographic extent than the theme from which you want to clip (input feature). In this exercise, you will use the California state outline (calif feature class) to clip the world ecological regions (eco feature class) to eliminate all areas outside of California. In other words, the clip feature is the California feature class, while the input feature is the eco feature class. Input Feature- + Clip Feature- = New Dataeco feature class calif feature class cal_eco feature class + = In ArcMap, most of the geoprocessing functions are located in the ArcToolbox. To access the toolbox, click on the Geoprocessing menu. Some of the most common tools are listed on the menu. Click on the Geoprocessing Menu, then Clip to bring up the Clip dialog box. The Input Feature is the layer you want to clip set it to Eco. The Clip Feature is the layer you will use to do the clipping set it to Calif. Set the Output Feature Class to C:\Temp\proj10\data\Project10.gdb\Cal_Eco. Once your Clip dialog box looks like the screenshot below, press OK You now have a cal_eco layer containing only the portion of the original eco layer that lies within California.
Before continuing, create a generalized ecological regions map of California: Zoom in to California. Turn off the eco and calif layers. Open the property file for cal_eco and go to the Symbology tab. Select Categories Unique Values. For your unique values map, use the generalized ecosystems data contained in the Mht_name field as your Value Field. Press the Add All Values button when creating the unique values map. Deselect the check next to <All other values>.
Tool #2 Dissolve If you zoom in on portions of California, you will see numerous adjacent polygons that are separated by a boundary line even though they share the same Mht_name value. The reason for this is that the Cal_eco layer also contains a more detailed classification system in a field called Ecoregion. You can confirm this by clicking with the Identify tool on any two adjacent polygons that have the same color. You will see that they have different values in the more detailed Ecoregion field. The interior boundaries separating polygons of the same color add considerable confusion to your map. To remove them, you will use a technique called Dissolve. This technique looks for polygons boundaries that separate two polygons having the same value and dissolves the line between them, thus creating one larger polygon. Input Layer + Dissolve tool = New Data cal_eco feature class cal_eco_dissolve feature class + Dissolve Tool = Another way to access the most popular geoprocessing tools is to click on the Geoprocessing menu. Click on the Geoprocessing menu, then click on Dissolve to open the Dissolve dialog box. Set the Input Features to Cal_Eco. Set the Output Features to C:\Temp\proj10\data\Project10.gdb\Cal_Eco_Dissolve. For the Dissolve Field, click the box next to Mht_name. Once the dialog box looks like the screenshot below, press OK. Note that the unneeded lines separating polygons with the same Mht_name value have been removed. Of course, the more detailed Ecoregions field is also gone since the detailed polygons needed for that field no longer exist.
Tool # 3 Buffer A buffer is a polygon shape whose outer boundary is a constant distance from another point, line or polygon feature or set of features. For this project, we ll assume you want to make a map of generalized ecoregions located within 25 miles of the California coast. Input Feature- + Buffer Tool- = New Data - calcoast feature class 25 miles coast_buf_25mi feature class + Buffer Tool = Add the calcoast feature class to your map. Click on the Geoprocessing menu, then Buffer to bring up the Buffer dialog box. Set the Input Features to calcoast. Set the Output Features to C:\temp\proj10\data\Project10.gdb\coast_buf_25mi. Set the Distance Units to Miles and enter 25 in the box immediately below the words Linear unit. Once your dialog box looks like the screenshot below, press Ok. Now that you have created the buffer, you can use it to clip the cal_eco_dissolve layer so that only the generalized ecoregions lying within 25 miles of the coast will show in your map. Follow the steps shown above for clipping and clip the cal_eco_dissolve layer with the coast_buf_25mi layer. Call the new layer coast_eco_buf25mi and save it in your Project10.gdb. You should now have a layer containing generalized ecoregions for the area lying within 25 miles of the California coast.
On Your Own Create the following map: Unique Values map showing the physiographic regions for the following states: Minnesota, Wisconsin, Michigan, Iowa, Illinois, Indiana, Ohio, Missouri, Arkansas, Tennessee, Kentucky PLUS Large airports within 50 miles of major cities in this region Dataset States Physio Major_Cities Attribute fields: NAME: State name Division: Physiographic regions NAME: City name Additional Datasets You must export this file from the Esri_data\data_maps_newest\usa\landmarks folder Airports NAME: Airport name TOT_ENP: Total Enplanement- Passenger boarding Things to consider: You will need to use clip to extract the physiographic regions found in the desired states. You will need to dissolve interior borders based on the Division attribute. The unique values map will be based on the Division attribute of the dissolved physio feature class. You should only show large airports (total enplanement greater than or equal to 2,500,000) within 50 miles of major cities in the desired region. The final map should include a locator map with the region one color and the rest of the US another color. You must include a scale bar, legend, north arrow, and title. Submit a color copy of your map layout. Challenge: If you want to try something new, search for pictures of the various physiographic regions and insert the pictures into your map layout. To insert pictures: Click on the Insert Menu Picture. Find the file on the computer and click open.