7.06 Infrastructure Sector Tutorial

Tue, 11/20/2007 - 10:32

Disclaimer: The objective of this tutorial is to get familiar with the GIS software. The tutorial only covers some parts that are being done in a real analysis. The results that are being displayed in the tutorial can’t be compared with the results a real analysis would generate.

Introduction

The objectives of this exercise are to get more familiar to some basic ArcGIS operations. We will create shapefiles, work with attribute data in Excel, digitize features to a new shapefile and join attributes to a shapefile.

The scenario of this exercise is that we will prepare an analysis based on road data to identify the bottlenecks of a road leading from the transport corridor at the municipal boundary where a major new settlement is located to the poblacion at the lake.

It should be noted that the procedure (digitizing an already digitized feature) in the tutorial is very unlikely to be used in real GIS applications. Rather, the existing road layer would be broken down in segments constituting a network, and the attribute data would be joined to the original, but modified, dataset. Constructing networks in ArcGIS is however an advanced task and a precondition is that the software is expanded to include network extension applications.

1 Getting started
1.1 Open ArcMap. Select A new empty map.
1.2 Add the following layers to the workspace:
Barangays_bndry
Roads

The first file is found in C:\CLUP_EXERCISE_DATA\00_BI\ and the two other files are all found in the \02_IS\ folder.

1.3 Assign proper symbology to the layers and rename them in the list of content. Since we will digitize the road layers, assign a line symbol with a rather large width (e.g. 3,0). See image below. To start changing the symbology, either double-click on the layer symbol in the table of content or open the Layer Properties window and select the Symbology tab.

1.4 In the menu bar click File > Save As… to save a map document as road_analysis_v1 in C:\CLUP_EXERCISE_DATA\. Don’t forget to save your progress now and then throughout the exercise.
2 Creating a shapefile
2.1 Open ArcCatalog (click on in the ArcMap tool bar).
2.2 In the catalog tree, navigate to the C:\CLUP_EXERCISE_DATA\02_IS\ folder. In the menu bar click File > New > Shapefile… The Create New Shapefile window appears.
2.3 Type the Name ‘RdAnalysis’ and select Polyline as Feature Type. See image below.

2.4 Assign the same coordinate system as the RdMun layer. First click Edit… to open the Spatial Reference Properties window. Click Import, browse for the RdMun layer and click OK. See image below.

2.5Click OK in the Spatial Reference Properties window. Click OK in the Create New Shapefile window. The new shapefile is created.
3 Digitizing
 
We will use GIS to show road segments that are in a critical or poor condition or have an inadequate width compare to road classification standards. The road will be digitized in segments where the nodes are defined at barangay crossings (so that the analysis can be used for comparisons between the barangays) and intersections with other roads (so network analyses can be made). In step 1.2 we added those files with road features and barangay boundaries to the workspace and we can thus proceed.

A good way to generate the road condition data is to print a map and use the paper map to make a sketch where the nodes should be located which will be the road segments before you start with the screen digitizing. Then the actual conditions of these road segments could then be verified in the field before it is digitized. A unique numerical ID will also have to be written and assigned in the sketch as to make field surveying and filing up the information easier and would also allow to easily assigned to corresponding ID to features that will be digitized.

3.1 Go back to the ArcMap window. (If you have closed it, you can start it again by clicking on in the ArcCatalog toolbar. If this is the case you also have to open the map document road_analysis_v1.mxd.)
3.2 Now it is time to add the shapefile we prepared for the analysis of the road condition. Click on and browse for RdAnalysis.shp. Click Add.

Nothing is seen on the map although the RdAnalysis layer is activated to be shown. The reason for this of course that no roads have yet been digitized into the layer. If you open the attribute table to the shapefile, you will find it empty, compare to image below. Now it’s time to start digitizing.

3.3 If it’s not already visible, you need to open the Editor toolbar. In the menu bar click Tools > Editor. The Editor toolbar appears. Drag and drop it to a suitable place in the workspace (e.g. within the toolbar).
3.4 In the Editor toolbar, click Editor > Start editing. See image below.

3.5Make sure that the settings are set to Create New Features and that the target layer is RdAnalysis. Click ???
3.6Set the snapping properties so that your digitizing effort will snap to vertices, along the line and the endpoints of both the RDAnalys_V1 and Roads layers and the edge of Barangay layer. In the editor menu, click Editor > Snapping… The Snapping Options appears between the table of content and your map (see image below). Select (check the corresponding box) according to what is mentioned above. You can now close the Snapping Options.

The plan is now to digitize as indicated below. A RdAnalysis line segment’s nodes will be at changes in road condition, crossings with barangay boundaries or intersections with other roads. For this exercise, we will assume that the changes in road condition falls directly within the intersection of the road with barangay boundary and road other roads. Note also that the ID used is just the order of roads that are to be digitized (top to bottom) and sequential numbering is used to make the exercise simpler.

3.7 Zoom in to segment 1 to a scale about 1:15000 or use the scale selector and the pan tool. (Now it will be easier to digitize.)
3.8 Refer to the image below. Start (click once) at the barangay boundary and follow the road and click again after a small section. Continue to click once at points along the road. End at the crossing of the road leading south by double-clicking to finalize the road segment. The result is shown in the second image below:



3.9 Assign another symbology to the RdAnalysis layer, so that your digital effort is clearly seen in the map. Choose for example a red and wide line symbol.

If you are not pleased with the result, use the redo button before you proceed with the next segment. Also get into the habit of saving (2) your work often. When you are finished or need to proceed with another GIS operation you should stop editing (1). Refer to image below.

3.10 Repeat step 3.8 on the other segments. Follow the order given in the sketch image just before step 3.7 above. When you’re done with this, your map should look something like this.

3.11 Click Editor > Stop Editing.
4 Assigning Road Segment ID to Conform with Attributes in the dBase File
4.1 Don’t close the editor. Open the attribute table by right-clicking on RdAnalysis in the list of content and selecting Open Attribute Table. The Attributes of RdAnalysis window appears. See image below. If you have followed the sketch above you should have ten segments in the table, each with its unique FID number. There is also another Id column that has zeros at the moment but needs to be identified in order to connect it with the attributes in the Excel/dBase tables.

4.2 So what ID should we give the segments? Well, there could be different alternatives. Here, we need to use the IDs that are found in the dBase file. decide to use the PSDG number of the barangay where the road segment is situated to give it its unique ID number. To facilitate we insert a name label for the barangays. In the table of content, right-click on the barangay boundary layer and select Properties.
4.3 The Layer Properties window appears (see image below). Go to the Labels tab. Select Label features in this layer. From the list menu to Label field select NAME. Click OK.

The result will look something like the image below and you see that in this case the road passes the barangays of Niyugan, As-is, Poblacion 1 and Poblacion 4.
The first segment is situated in a barangay named Niyugan, which has a barangay ID (0)1. We assume that we do not need to divide a road into more than 99 segments in a barangay. As this segment is the first we give it the unique ID of 101.

4.4 Make sure that you are still in editing mode. (If not choose Editor > Start Editing from the editor toolbar.) Return to or open the attribute table (refer to step 4.1 if needed).
4.5 Place the cursor in the first row in the Id column in the Attributes of RdAnalysis table window. Click once and type 1401 for FID0. (Since As-is barangay ID is 14 and this constitutes the first road segment in barangay.)
4.6 Providing that you digitized the same segments in the same order as in the sketch above, repeat step 4.5 on the other rows and assign Id according to the table/image below:.

4.7 Click Editor > Save Editing.
4.8 Also make sure to save the map document road_analysis_v1 by either clicking on in the toolbar or selecting File > Save in the menu bar.
5 Converting the Attribute Excel File to dBase Format
 
We will now work on the dBase Table with additional attribute data of the road. (This data has been captured on ground within a field survey and entered into an excel file.) When working with Excel, it is always recommended that ArcMap is closed (and vice versa). This is due to avoid accessing the same files from the two programs, which can lead to quite some problems. If you have a printed sketch map with the segments, also add the new Id numbers onto this map.

5.1 Close ArcMap. Open Excel.
5.2 Open the file IS01_RdTp2007.xls found in C:\CLUP_EXERCISE_DATA\02_IS\. (See image below where, for example, the road segment with ID 101 is municipal road, has a gravel surface and is in a poor condition.

5.3 Select (highlight) the cells that will be found in the dBase file. (Place the cursor in cell B2 and drag it to cell H12.) From the excel menu bar, select Edit > Copy.
5.4 Open a new file. (Go to File > New then select New empty document.) Place the cursor in cell A1 and select Edit > Paste. See image below.

5.5 The head column must be in one line in dBase format. Select the cells constituting the column head (A1:G1). From the menu bar select Format > Column > AutoFit Selection.
5.6 Only one sheet is allowed in dBase. Remove Sheet 2 by right-clicking on the Sheet2 tab and selecting Delete. (See image below.) Repeat this procedure on Sheet 3:

5.7 Select only the cells with data (A1:G9). Select File > Save as…
5.8 In the Save As window, browse for the folder C:\CLUP_EXERCISE_DATA\02_IS\ and type the File name IS01_RdTp2007.dbf. From the Save as type menu list, select the DBF 4 (dBASE IV) (*dbf) option. Click Save.
5.9 Now a couple of alerts will appear one after each other. Simply click OK to the alert as below:

5.10 Click Yes to the alert below:

5.11 Click the exit button (1) and Yes (2) below.

5.12 Click OK again

5.13 Finally, click Yes.

5.14 Close Excel.
 
It’s always recommended to have Excel closed when you work with ArcGIS.
If you want to revise a .dbf file you should close ArcGIS before you open Excel.

6 Joining the dBase File to the Shapefile
6.1 Open ArcMap and the map document road_analysis_v1.
6.2 In the table of content, right-click on RdAnalysis and select Joins and Relates > Join… (see image below).

6.3 The Join Data window appears. (See image below.) You should have the following settings:
1.’ Id’ was the column head where you inserted the unique Ids for the road segments
2. ‘IS01_RdYr’ is the name of the dBase table you have prepared that contains the attribute information of the road segments.
3. RD_ID is the name of the column where the unique ID have been inserted
4. Click OK.

7 Viewing the Result of the Analysis
7.1 Open the attribute table for the RdAnalysis layer. As you can see, the columns from the dBase table have been intergrated.
7.2 To make the table easier to read we need to hide some columns and give proper alias. Open the Layer Properties window and go to the Fields tab.
7.3 Place the cursor on the first row (RDAnalysis.FID). This is ArcGIS’s column with little information value for us. Therefore, unselect the Visible box. (See image below.)

7.4 Repeat step 7.3 for the consecutive fields. If a field is selected visible, you should assign a more understandable Alias.
Set the following fields to be visible and assign the respective alias:
IS01_Rd_ - ‘Road Segment ID’
ISO1_Rd_ - ‘Road Classification’
Etc…
  You have completed the exercise! Well done.
You can now think of different ways to present the analysis. Test the “interactive presentation” by using the Identify tool on the Rd_analysis layer. Since you’ve set the fields display properties above and thus reduced redundant and unnecessary information, the result will be fairly easy to interpret for a “normal” computer user.

Ver 1.0


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