GEOG 4/575 Lab 5: Spatial Data Editing and Topology

 

Due Nov 4.

 

            You will use ArcMap's editor, topology editor, and spatial adjustment tools to edit features in shapefiles and geodatabase feature classes. These are fundamental skills in digital map compilation and spatial data automation. Map editing is an intricate task both in terms of using the GUI and doing the sketch. You need to pay extra attention to the steps described in the text. If you miss one step, then the subsequent steps might not be working the way you expect. You can always undo your editing and restore the data back to where you last saved your edits.

 

            Finish all tasks in Chang's Chapter 7. Answer and submit all questions listed at the end of this exercise. Lab exercise data are available in: I:\Students\Instructors\Geoffrey_Duh\GEOG4575\Chang_5e\chap7 (or on the textbook CD). Please copy all these folders to your working directory in c:\Users before you start.

 

Additional Notes for ArcGIS 10 Users:

 

You have used the new snapping environment or the classic snapping environment in ArcGIS 10 in Lab 3. There are other major changes in ArcGIS 10's new editing environment. Please see these on-line resources for more information.

 

What's new for editing in ArcGIS 10

Editing in ArcGIS Desktop 10 (Web presentation)

 

Here is a quick summary to help you get started with this lab. The first major change is the workspace-based editing session in ArcGIS 10. A workspace is a geodatabase feature dataset or a folder containing several shapefiles. When a user starts an editing session, ArcMap layers from the same workspace can be edited. You will see a list of feature templates (i.e., layers in the workspace that are also displayed in ArcMap) created automatically when you start editing. You can select a template and one of its various new feature construction tools to create new features. When modifying existing features, you select the intended tools (e.g., Edit Vertices, Reshape Feature, or Cut Polygon tool) from the Editor toolbar and apply the them on the features directly. There is no longer an option to specify a "target layer" on the Editor toolbar. In most editing modes, you can double-click and select the Finish Sketch (F2) to complete an editing task. Here are the additional instructions to complete Tasks. You can also change the Table of Content to the List by Selection view so that you can verify which features are selected from which layers.

 

Task 1, Step 3. Cut polygon 71.

1.      Zoom into polygon 71.

2.      Use the Edit tool to select polygon 71 by clicking inside the polygon. Polygon 71 is highlighted when it's selected.

3.      Click on the Cut Polygon tool on the Editor toolbar. Move the mouse cursor over the location where the reference layer (red line) intersect the target layer (black line) until a square box shows up and indicates that you have snapped to the vertex of editmap2. Click the mouse to create the first point.

4.      Now you should see a red marker placed on where you clicked and a Feature Construction mini-toolbar appeared. Click on the Trace icon on the mini-toolbar and click on the red marker you just created. Move the mouse cursor along the red reference line until it snaps to the other edge of polygon 71. When in trace mode, you will see a green highlighted line following the mouse cursor as it moves.

5.      Click the mouse at the intersection of the red and black lines. Right-click the mouse and select Finish Sketch to complete the editing task.

6.      You should see polygon 71 is cut into two polygons. You can now click the Attributes tool on the Editor toolbar to open the attribute editing window and update the attributes of the polygons you just created.

 

Task 1, Step 5. Reshape polygon 73. Please follow the Step 4 instructions on the textbook to start the process.

1.      You will see the Edit Vertices mini-toolbar when you double-click on the outline of polygon 73. Select the Add Vertex tool on the mini-toolbar to continue the task.

2.      Alternatively, you can create a new polygon that follows the reference boundaries (red line) next to polygon 73 (using the Auto Complete Polygon tool on the Create Features window), then follow the Step 2 instructions to merge polygons 73 and the polygon you just created.

 

Task 2, Step 1. Delete the feature template of land_dig from the Create Features window. This prevents the features in land_dig from being modified by the cluster tolerance adjustment. Follow the instructions on the textbook to complete this task.

 

Task 3, Step 6. Ignore the snap settings described in the textbook. Instead, use the default ArcGIS 10 snapping settings to complete this step. When creating a new feature, you need to select the feature template and use the tool appeared in the Construction Tools panel to add the new feature.

 

Task 4. When you encounter file lock error problems in ArcGIS, the best way to resolve the problem is to close all ArcGIS products and restart ArcMap.

 

Task 5, Step 1. First use the Define Projection tool (or the Properties dialog window) to set the projection of both mrblemtn and hoytmtn feature classes to "NAD_1983_UTM_Zone_18N". Then, use ArcCatalog to export the hoytmtn to a shapefile. Save the shapefile with the same name in your Lab folder. You will need the shapefile to produce the map for Question 2.

 

Task 5, Step 2. Select the Start Editing from the Editor's dropdown menu and ignore the snap settings described in the textbook.

 

Task 5, Step 3. Set the Adjustment Methods to Rubbersheet. Make sure when setting the Options of Spatial Adjustment toolbar the method for Rubbersheeting is set to Natural Neighbor.

 

Task 5, Step 5. You will need to zoom in really close to see the link arrows. Each time you apply the Edge Match tool, matched links are added to a link table. Repeatedly applying the Edge Match tool on the same location creates multiple links for the same pairs of points to be matched. This is why the numbers of links that you create might be different from what the text indicates. This will not affect the adjustment.

 

Task 5, Additional step. After the two feature classes are edgematched, use the MERGE tool to combine them into one feature class and save it in the personal geodatabase. Then use the DISSOLVE tool to remove the artificial boundary on the merged feature class. On the DISSOLVE tool dialog, specify MINOR1 as the dissolve field and uncheck the "Create Multipart Feature" checkbox.

 

Questions:

1) If you had entered 10 meters for the cluster tolerance in Task 2, Step 2, what would have happened to trial_dig and land_dig? Provide pictures (i.e., screenshots) to illustrate.

2) Produce a map showing the original maps (hoytmtn & mrblemtn) used in Task 5 and the final dissolved map (produced in Task 5's additional step using the MERGE and DISSOLVE tools).  Also insert one or two screenshots of the blow-up view of the adjustments to illustrate the effect of edgematch. If you didn't make a copy of the hoytmtn, you can find the unadjusted original hoytmtn featureclass in the instructor's folder.