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Lab: Editing Data - Introduction Computer Mapping and GIS | GEOG 250, Lab Reports of Geography

Fort Lewis College (FLC)Geography
Prof. William S. White

Material Type: Lab; Professor: White; Class: Intro Computer Mapping & GIS; Subject: Geography; University: Fort Lewis College; Term: Unknown 1989;

Typology: Lab Reports

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GEOG 300: Intermediate GIS: Vector-based Analysis
ArcGIS Exercise #7b: Editing Spatial Data, part II
Main Objective: To investigate some of the data model creation and spatial data editing tools and
functions in ArcMap using data from ESRI.
Introduction: Today’s lab consists of three exercises that have been modified from the ESRI Virtual
Campus. You do not need to access the Virtual Campus web page in order to finish the exercises.
Some of the text for this exercise has been taken directly from the Virtual Campus; some has been
changed to suit our particular needs this week. Within each exercise are some general questions for you
to answer – type your answers in Microsoft Word. The questions can be answered through your work on
the exercise, and using ArcGIS Desktop Help. There are also two maps to complete and print out.
Note: A full-color version (whoopee!!!) of this lab document can be found in the lab7b folder.
Exercise 1: Working with a Data Model and Geodatabase Schema
1. You will need about 10 MB of space on your flash drive to complete this lab exercise. Copy the lab7b folder
located in O:\GIS\geog300 to your M:\geog300 folder.
2. Start ArcCatalog. In the Catalog tree (left hand side of ArcCatalog), navigate to your M:\geog300\lab7b folder.
Right click on this folder, and choose New>>File Geodatabase. Name the geodatabase FarmLand.gdb. A
file geodatabase is an ESRI-specific file structure used primarily to store, query, and manipulate spatial data.
Geodatabases store feature geometry (shape), a spatial reference system, attributes, and behavioral rules for
data. Various types of geographic datasets can be collected within a geodatabase, including feature classes,
attribute tables, raster datasets, network datasets, topologies, and many others.
3. ArcCatalog includes a special tool called the Schema Wizard that is used to convert data models into geodatabase
schemas. A schema defines the structure of your geodatabase. You need to add it to the ArcCatalog user interface.
Go to Tools>>Customize. In the Customize dialog box, click the Commands tab. In the Categories list, click Case
Tools. Under Commands, click the Schema Wizard icon and hold your mouse button down, then drag and drop the
icon onto the end of the Standard toolbar. This is the toolbar with 21 icons; the Schema Wizard tool will be your 22nd.
Close the Customize dialog.
4. In ESRI’s ArcGIS terminology, a data model can be a type of a
diagram that illustrates the geodatabase design. The greatest
advantage of a data model is that the logical and relational decisions
of the database structure have already been performed. Specifically,
the FarmLand data model looks like the diagram to the right. It's not
important that you understand the specifics of the model right now.
What is important is that you recognize some of the database
structural elements depicted by the diagram. There are five objects in
this diagram: two coded value domains, a standalone feature class, a
feature dataset (with a single feature class), and a table. A ―coded
value domain‖ is a type of attribute domain that defines a set of
permissible values for an attribute in a geodatabase. Coded value
domains consist of a code and its equivalent value. In the FarmLand
data model, there are three coded value domains that the attribute
LandUseCode can carry: AGR, CRP, and HMS. There are two coded
value domains that the RoadCode attribute can carry: M and X.
Within the FarmLand data model is one standalone feature class,
Roads. This feature class consists of polylines that can be identified
by attributes as either 1 (County) or 2 (Private). In geodatabases, a
subset of features in a feature class or objects in a table that share
the same attributes is called a subtype. The feature dataset Land,
has one feature class Landuse. This feature class is composed of
polygon features that can carry three attributes. Finally, a
LandUseLookUp table is also a part of this data model.
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Download Lab: Editing Data - Introduction Computer Mapping and GIS | GEOG 250 and more Lab Reports Geography in PDF only on Docsity!

GEOG 300: Intermediate GIS: Vector-based Analysis

ArcGIS Exercise #7b: Editing Spatial Data, part II

Main Objective : To investigate some of the data model creation and spatial data editing tools and

functions in ArcMap using data from ESRI.

Introduction : Today’s lab consists of three exercises that have been modified from the ESRI Virtual

Campus. You do not need to access the Virtual Campus web page in order to finish the exercises.

Some of the text for this exercise has been taken directly from the Virtual Campus; some has been

changed to suit our particular needs this week. Within each exercise are some general questions for you

to answer – type your answers in Microsoft Word. The questions can be answered through your work on

the exercise, and using ArcGIS Desktop Help. There are also two maps to complete and print out.

Note: A full-color version (whoopee!!!) of this lab document can be found in the lab7b folder.

Exercise 1: Working with a Data Model and Geodatabase Schema

  1. You will need about 10 MB of space on your flash drive to complete this lab exercise. Copy the lab7b folder located in O:\GIS\geog300 to your M:\geog300 folder.
  2. Start ArcCatalog. In the Catalog tree (left hand side of ArcCatalog), navigate to your M:\geog300\lab7b folder. Right click on this folder, and choose New>>File Geodatabase. Name the geodatabase FarmLand.gdb. A file geodatabase is an ESRI-specific file structure used primarily to store, query, and manipulate spatial data. Geodatabases store feature geometry (shape), a spatial reference system, attributes, and behavioral rules for data. Various types of geographic datasets can be collected within a geodatabase, including feature classes, attribute tables, raster datasets, network datasets, topologies, and many others.
  3. ArcCatalog includes a special tool called the Schema Wizard that is used to convert data models into geodatabase schemas. A schema defines the structure of your geodatabase. You need to add it to the ArcCatalog user interface. Go to Tools>>Customize. In the Customize dialog box, click the Commands tab. In the Categories list, click Case Tools. Under Commands, click the Schema Wizard icon and hold your mouse button down, then drag and drop the icon onto the end of the Standard toolbar. This is the toolbar with 21 icons; the Schema Wizard tool will be your 22nd. Close the Customize dialog.
  4. In ESRI’s ArcGIS terminology, a data model can be a type of a diagram that illustrates the geodatabase design. The greatest advantage of a data model is that the logical and relational decisions of the database structure have already been performed. Specifically, the FarmLand data model looks like the diagram to the right. It's not important that you understand the specifics of the model right now. What is important is that you recognize some of the database structural elements depicted by the diagram. There are five objects in this diagram: two coded value domains, a standalone feature class, a feature dataset (with a single feature class), and a table. A ―coded value domain‖ is a type of attribute domain that defines a set of permissible values for an attribute in a geodatabase. Coded value domains consist of a code and its equivalent value. In the FarmLand data model, there are three coded value domains that the attribute LandUseCode can carry: AGR, CRP, and HMS. There are two coded value domains that the RoadCode attribute can carry: M and X. Within the FarmLand data model is one standalone feature class, Roads. This feature class consists of polylines that can be identified by attributes as either 1 (County) or 2 (Private). In geodatabases, a subset of features in a feature class or objects in a table that share the same attributes is called a subtype. The feature dataset Land , has one feature class Landuse. This feature class is composed of polygon features that can carry three attributes. Finally, a LandUseLookUp table is also a part of this data model.

QUESTION 1:

Which of the following is not a subtype (attribute) of the Landuse feature class: Counties, Agricultural, CRP, or Homestead?

  1. Once designed, a data model can be exported to an XML file format, which in turn can be converted into a geodatabase schema using the Schema Wizard. XML (extensible markup language) is a type of text formatting. In the Catalog tree, click once on the FarmLand geodatabase ( FarmLand.gdb ) that you created earlier. This is where the schema will be generated. Click the Schema Wizard button you added to the Standard toolbar. In the Schema Wizard, click Next to move to the second panel. Make sure the option for Model stored in XMI file is selected. According to ESRI, XMI is a metadata interchange file format used for saving ESRI data models in XML format. Click the Browse button and navigate to *M:\geog300\lab7b* CreateFeatures. Choose FarmLandModel. Click Open. Click Next. Select ―Use default values‖. Click Next. A preview of the geodatabase schema is presented to you.
  2. The Schema Wizard provides you with opportunities to modify the properties of the geodatabase components defined by the data model. In this step, you will define the spatial reference for the feature classes. Click Roads, then click the Properties button. On the General tab of the Roads Properties dialog, notice that the Spatial Reference is an Unknown Coordinate System. Click the button with the three little dots (the ellipsis button). Import the spatial reference from the Kansas_area.sid image located in your *M:\geog300\lab7b* CreateFeatures folder. Click OK to return to the Schema Wizard. Now set the spatial reference for the Land feature dataset in the same way. Click Land, then click the Properties button. Notice that the Feature Dataset Properties dialog is different than the Roads Properties dialog. Click the Edit button instead of an ellipsis button to change the spatial reference. Once again, import the spatial reference from the Kansas_area.sid image. Feature classes inherit the spatial reference information from the feature dataset that they reside in, so by setting the spatial reference for the Land feature dataset, the spatial reference information for the Landuse feature class is also set. Once you're back to the Schema Wizard, click Next. A summary of your work in the Schema Wizard is provided. Click Finish. When prompted to see the log file, click No.
  3. In the Catalog tree (the left side of ArcCatalog), expand the FarmLand geodatabase and the Land feature dataset. All of the components and component properties of the data model have been translated into a geodatabase schema. Right-click FarmLand , then click Properties. When the Database Properties dialog opens, click the Domains tab. Notice that two coded value domains are part of this geodatabase. Click each of the domain names to see their coded values at the bottom of the dialog. Close the Database Properties dialog. Open the Properties dialog for the Landuse feature class (inside the Land feature dataset) and click the Subtypes tab. The subtype codes and descriptions are shown. Close the Landuse Properties dialog. Open the Properties dialog for the LandUseLookUp table. On the Fields tab, under Field Name, click LuAbrev. The Field Properties panel appears in the dialog. In the Field Properties panel, click the blank cell to the right of Domain. Choose LandUseCode from the dropdown list. Click OK to close the Table Properties dialog. Open the Properties dialog for the Roads feature class. Click the Subtypes tab, if necessary. In the Roads attribute table, the RoadSubtype field will be populated with one of two subtype codes: 1 or 2. The code description indicates what the subtype code stands for. Under Default Values and Domains, notice that the RoadCode field is listed. You can select a domain for each subtype. In this exercise, you will use the same domain for both subtypes. Click 1 under Code. Under Default Values and Domains, click the blank Domain cell for RoadCode. Select RoadCode from the dropdown list. The values in the RoadCode domain will used to populate the RoadCode field for Subtype 1 (County). Click 2 under Code. Again, click the blank Domain cell for RoadCode and select RoadCode from the dropdown list. Now both subtypes are using the same domain. This means that you will be able to classify road features based on two attributes: subtype (1 = County or 2 = Private) and road code (M = Maintained or X = Not maintained). Click OK to close the Feature Class Properties dialog. Examine the properties of the FarmLand geodatabase, including its feature classes and tables.

For now, you will represent any curved features with small linear segments. In the next exercise, you will learn how to create true curves. If you want to start over, revise your sketch, or modify the new feature after you've completed it, use the methods below:

Action Steps Delete a vertex in a sketch Right-click the vertex >> click Delete Vertex Delete a sketch Right-click >> click Delete Sketch Delete a new feature Select feature with Edit tool >> press Delete key Insert a vertex in a feature Double-click feature with Edit tool >> right-click at insert location >> click Insert Vertex

From the View menu, point to Bookmarks and choose StartDigitizing. Click the Sketch tool , then click the Start point shown in the graphic below. Follow the sequence shown, clicking along the right side of the road so the landuse layer does not overlap the roads layer (which you will digitize later). Use only as many vertices as you need to properly describe the farmland area and use the Pan shortcut key (C) as necessary.

Tip: At this point, the Landuse and the Roads layers are still empty. When there is an empty layer in your map document, you cannot use the Zoom to Full Extent button. If you want to get an overview, right-click the Kansas_area.sid image and zoom to the layer instead.

When you're finished, click the End point, then press F2 to finish the sketch. In the Table of Contents, right- click the Kansas_area.sid image and click Zoom to Layer to see the polygon you just digitized. If you're happy with your sketch, from the Editor menu, click Save Edits. If you want to try again, click the Undo button and start over. Save your edits when you're satisfied with the results. With the newly digitized feature still selected, click the Attributes button on the Editor toolbar. Notice that the value for LuSubtype is Agricultural. In the next steps, you will digitize and code the other types of landuse.

QUESTION 4: How was the feature that you just digitized, “automatically” designated as Agricultural?

Close the Attributes dialog.

  1. You can create additional features from an existing feature by using the Cut Polygon Features task. On the Editor toolbar, change the task to Cut Polygon Features. Change your view to the Homestead1 bookmark. Make sure the Landuse polygon that you just created is selected (If not, select it with the Edit tool ). Digitize the homestead using the Sketch tool. You will create five new homestead polygon features by cutting them out of the Landuse polygon you just digitized, in the sequence shown at the top of the next page:

Move your mouse pointer to your start point, as shown below. Notice how your pointer snaps to the Landuse polygon edge and a small text box appears. This is your snap tip–it ensures you are placing your new vertex at the correct place.

While snapped to the Landuse polygon edge, click to start and then digitize in a clockwise direction. To finish, snap to and double-click the Landuse polygon edge. Right-click the Landuse layer and choose Zoom to layer. Now digitize homesteads 2, 3, and 4 in the same manner. Make sure you Select the large light green polygon with the Edit tool before you start to digitize a homestead. For homestead 5, finish the sketch by snapping to the start point, then double-clicking. When you’re finished, zoom to the extent of the Landuse layer. Your map should look similar to the graphic on the top of the next page.

After digitizing the reserve area’s shape, clear the selected features. With the Edit tool, click in the middle of the polygon you just digitized so that only it is selected. Update its attributes by assigning it to the Conservation Reserve Program (CRP) landuse subtype. Save your edits and clear the selected features. Zoom to the extent of the base layer.

  1. To create the road features, you will digitize a line which approximately represents their centerlines. Change the task to Create New Feature. Change the target to Roads : County. For now, the features you will digitize will be created in the Roads feature class and belong to the County subtype. Later, you will assign the private roads to the Private subtype. Set the Selectable Layers to include Roads as well as Landuse. Add Roads - Edge and End as snap agents.
  2. In this step, you will use the Trace tool to digitize the road along the perimeter of the farmland area, using an offset so the road will be created parallel to the landuse features, not coincident with them. In the Table of Contents, right-click Landuse, and choose Selection>>Select All. From the tool palette on the Editor toolbar, click the Trace tool. This is underneath the Sketch tool (pencil icon). Because you will digitize the road centerline, you will set the offset distance to be one-half the width of the roads. Press O on your keyboard. In the Trace Option dialog, enter -10 for the offset. Make sure that the box next to Remove self-intersecting loops is checked and keep the default values for the other fields. Click OK.

QUESTION 5: Why did you enter a negative value for the offset distance?

Zoom to the start location shown in the graphic below (to clearly see the line created by the Trace tool, set your scale to 1:1,100). With the Trace tool, snap to the selected Landuse polygon edge. Click once on the corner and then without clicking any mouse buttons, begin to move the pointer north along the Landuse polygon edge, as shown below:

As you trace over the Landuse polygon edge, notice the new sketch being created by the Trace tool to the left of the direction of travel. Now zoom to the extent of the base layer. Continue tracing the outside edge of the Landuse features in a clockwise direction. Tip: As you're tracing, keep your mouse pointer slightly outside the Landuse polygon to avoid accidentally tracing the interior perimeter of the homestead polygons. When you're done, double-click the start point to finish the sketch. Save your edits and clear selected features.

  1. In this step, you will digitize the homestead driveways and then the remaining roads inside the landuse polygon. First, turn off all snap agents in the Landuse layer; leave the two Roads snap agents (Edge and End) alone. Use the graphic on the next page as a guide to digitize the six driveways shown in yellow. Zoom in as much as you need to and digitize in a clockwise direction. Use the Sketch tool to create the driveway features and make sure you snap driveways 1-5 to the edge of the perimeter road. Note: The driveways are not easily discernable in the aerial photograph, but do your best to place them. To see the road features more clearly, try turning off the Landuse layer.

Now digitize the remaining roads inside the landuse polygon, using the graphic below as a guide for snapping. The roads you will digitize are shown below in dark gray. Create two separate road features: Road 1 from north of the homestead 2 driveway, around the CRP land, and ending at the start of the homestead 6 driveway, and Road 2 from the start of the homestead 6 driveway to the end of the homestead 5 driveway.

When you're done, save your edits, and then clear the selected features. Zoom to the full extent.

  1. Now you will update the Roads feature class attributes by assigning ownership and maintenance codes. The ownership code shows whether a road is owned by the county or privately, and the maintenance code shows if the county is responsible for maintaining a road or not. Select all Roads features, then click the Attributes button. Move the Attributes dialog out of the way so you can see it and the map display simultaneously. For each feature, assign the correct ownership and maintenance codes using the graphic on the next page as a guide. Tip: Click a listed feature in the left panel to flash that feature on the map. When you're done, close the Attributes dialog, save your edits, and clear selected features.

Exercise 3: Editing Street Centerlines

In this exercise, you will digitize street centerlines on top of an aerial photo. You already know how to create street centerlines using the Trace tool from the previous exercise. In this exercise, you will use the more precise method offered by the Midpoint tool to create the straight segments of the street centerlines. For the curved segments, you will use the Tangent tool and the End Point Arc tool. A layer of digitizing reference points will assist you in defining the start and endpoints, as well as the radius of the curves.

  1. Start ArcMap, if it is not already running. Navigate to your M:\geog300\lab7b folder and open TrailerParkI.mxd. The map document shows an aerial photo of the Walnut Grove trailer park area, a Streets layer, and a Reference Points layer to help you with your digitizing tasks. The streets are divided into arterial (red), collector (green), and local (orange) subtypes. All local streets east of the red arterial street belong to the trailer park. In the southern part of the trailer park, two concentric circular streets and two adjoining streets have been recently built.
  2. Start an edit session by clicking on the Editor Toolbar icon. Dock the toolbar horizontally beneath the Standard toolbar icons. Set the digitizing parameters as shown below:

Parameter Setting Steps Target Streets: Local Editor toolbar > Target dropdown list Snap agents  Reference Points-Vertex  Streets-Vertex Editor menu > Snapping Snapping tolerance 10 map units (not pixels) Editor menu > Options > General tab  Show snap tips Selectable layers Streets Selection menu > Set Selectable Layers

  1. Now you are ready to create street centerline features. First you will connect your new sketch to the existing street network by snapping to an existing street centerline vertex. Then you will use the Midpoint tool to place the vertices of the new feature exactly in the center of the street. Change your view to Bookmark 1. The bookmark shows the street that connects the trailer park to the green collector street at the south end of the trailer park. On the Editor toolbar, click the Edit tool. Double-click the green collector street at the bottom of the map to display its vertices. Notice the vertex in the center of the T-intersection. You will begin your sketch at this location. Click the Clear Selected Features button.

Change your view to Bookmark 2. This bookmark zooms to the T-intersection. Set the task to Create New Feature. Click the Sketch tool. Move your mouse pointer along the green Collector street feature until it snaps to the vertex at the T-intersection. The snap tip tells you that you are snapping to a vertex of the Streets layer. Click once. Click the Midpoint tool from the tool palette. Click on the left edge of the street, then click on the right edge directly across the street as shown by the arrows in the graphic on the right, creating a pair of defining points. A vertex is added at the midpoint between the two points you clicked.

Change your view to Bookmark 3. You are looking at the top part of the street just before it starts to curve. Use the Midpoint tool again to place another vertex just before the street starts to curve, placing your defining points at the locations indicated by the second graphic to the right.

Change your view back to Bookmark 1.

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2

  1. In this step, you will use the Endpoint Arc tool to continue the street centerline with a true curve, defining the midpoint of the curve by entering an explicit radius value. Change your view to Bookmark 4. From the tool palette, click the End Point Arc tool. Click once in the center of the street just after the curve, as shown by the arrow in the graphic on the right. Use an imaginary line through Reference Point 1 to determine the center of the street. Move your mouse pointer very slightly to the right, then press R on your keyboard. In the Radius dialog, type 100 and press Enter. Click the Sketch tool. Move your mouse pointer toward Reference Point 1 until it snaps and click once to add a vertex.

Change your view to Bookmark 1. Now snap your mouse pointer to Reference Point 5 and double-click to finish the sketch. On the Editor toolbar, click the Attributes button. Click the Value column next to NAME and type in Potomac. Click the Value column next to TYPE and choose Rd from the dropdown list. Close the Attributes dialog and clear the selected features. Zoom to the full extent, then save your edits.

  1. You are now going to digitize the concentric circular streets that intersect Potomac Road. In the previous step, you set the radius of the arc by typing it into the Radius dialog. In this step, you will set the radius visually by moving the mouse pointer and clicking at the desired location. Change your view to Bookmark 5. From the tool palette, click the End Point Arc tool. Click Reference Point 1 once. Now click Reference Point 2 once. Finally, click Reference Point 3 once. To close the circle, click Reference Point 1 again, then double-click Reference Point 4. Click the Attributes button and name the street Johnstowne Cir. Close the Attributes dialog.

Using the same method, digitize the inner circle with the Endpoint Arc tool starting at Reference Point 5. Don’t forget that you can always click the Undo button if you make a mistake. Name the inner street Milltowne Cir. Close the Attributes dialog and clear the selected features. Zoom to the full extent and save your edits.

  1. Using the Tangent tool , you will now digitize the slightly curved road that connects the southern end of the trailer park with the rest of the neighborhood. This is a continuation of Potomac Road, which breaks at the inner circular street. Change the view to Bookmark 6. On the tool palette, notice that the Tangent tool button is inactive. This tool becomes enabled only if there is at least one sketch segment present. Using the Sketch tool, click Reference Point 6 once, then click Reference Point 2 once.

Change your view to Bookmark 7. Click the Midpoint tool. Click the left edge of the street just before the street starts to curve, then click the right edge of the street directly across from the previous point, as indicated in the graphic on the right. Click the Tangent tool. At the top of your screen, double-click the vertex at the intersection of the two street centerlines. Name the street Potomac Rd. , then clear the selected features. Zoom to the full extent of the document.

  1. Stop editing and click Yes to save your edits when prompted. Save the map document as TrailerParkI_final.mxd in your M:\geog300\lab7b folder.
  2. Turn off the Reference Points and Walnut Grove map layers.
  3. Open the attribute table for the Streets map layer. Notice that the lines and polylines are attributed with names ( NAME field) and types ( TYPE field – Ave, Rd, Blvd, etc.). Close the Attribute table.

3