Spatial Query - Box Select

• Enforcement Task - Commercial Areas Crashes
  

  To begin, first proceed through the process to identify your region of interest. That is, begin by selecting ALAS File from the menubar, then select View Map from this menu. Proceed through the questions, selecting the region type (County), the region desired (Story), the timeframe of interest (1993-1997), and whether you want to use actual crash locations or nodes for your selection (choose actual crash locations). Once this has been completed, you should have a map showing Story County roads, rails, rivers, and 1993-1997 crashes, shown in Figure 1.

  

  Figure 1. Story County map

  Using the zoom-in tool, zoom to the Ames area (the large city on the western edge of the map). First, move the mouse pointer to the zoom-in tool button () and click with the mouse to select it. Then proceed by placing the zoom button at one corner of a box that would contain Ames, pressing and holding down the left mouse button, dragging the mouse to the opposite corner of the box, and releasing the button. The box to be drawn (though difficult to see) is shown in Figure 2.

  

  Figure 2. Zoom-in box

  The resultant map should look somewhat like the one shown in Figure 3.

  

  Figure 3. City of Ames map

  Next, using the box selection tool, select the Ames downtown region, the North Grand Mall region, and the Ames campustown region, as shown in Figure 4. First, move the mouse pointer to the box select tool button () and click with the mouse to select it. Then proceed by placing the zoom button at one corner of a box that would contain downtown Ames, pressing and holding down the left mouse button, dragging the mouse to the opposite corner of the box, and releasing the button. While holding down the shift key on the keyboard, repeat this process for the other two regions. The box to be drawn for the Ames downtown region (though difficult to see, is shown in Figure 4.

  

  Figure 4. Box selection of downtown Ames

  The resultant map should look somewhat like the one shown in Figure 5.

  

  Figure 5. Ames commercial areas selection

  From here, select Request from the menubar, then select Crash Locations from this menu. A box giving the number of crashes for the selected region will then appear. An example of the answer is shown in Figure 6. Note: You should only arrive at the same answer if you selected the EXACT same region as is selected here.

  

  Figure 6. Results of crash selection

  Another dialog box, shown in Figure 7, will appear, asking if you wish to zoom to the selected crashes.

  

  Figure 7. Zoom dialog

  Click on "Yes". The screen will redraw, zooming to the region of selected crashes, as shown in Figure 8.

  

  Figure 8. Selected region

  You may now proceed by selecting various parameters and producing reports, as outlined in the AV-ALAS User's Manual. Additionally, if you wish to zoom back to the previous zoom level, select View from the menubar, then select Zoom Previous from this menu.

  Additionally, you could, once the crashes have been selected, quickly determine the number of crashes that have occurred in each year. This can be done two ways.

  • First, you could select Theme from the menubar, then select Table from this menu. This would result in a number of tables opening, one for each year selected. When each table is made the active table (i.e., the one in use at the time), the number of crashes selected as well as the number of crashes total for that year will be displayed in the upper left of the ArcView window.

  • Second, you could make each theme for each year active one at a time and then select Request then Crash Locations for each theme. The total number of selected crashes for that year would then be returned.

  Potential uses for box selections are numerous. They are the basis for all further operations within ArcView ALAS whether you are selecting a group of crashes or a group of nodes.

Enforcement Task - Crashes within 1/2 mile of university housing

To begin, first proceed through the process to identify your region of interest. That is, begin by selecting ALAS File from the menubar, then select View Map from this menu. Proceed through the questions, selecting the region type (County), the region desired (Story), the timeframe of interest (1993-1997), and whether you want to use actual crash locations or nodes for your selection (choose actual crash locations). Once this has been completed, you should have a map showing Story County roads, rails, rivers, and 1993-1997 crashes, shown in Figure 1.

Using the zoom-in tool, zoom to the Ames area (the large city on the western edge of the map). First, move the mouse pointer to the zoom-in tool button () and click with the mouse to select it. Then proceed by placing the zoom button at one corner of a box that would contain Ames, pressing and holding down the left mouse button, dragging the mouse to the opposite corner of the box, and releasing the button. The box to be drawn (though difficult to see) is shown in Figure 2. The resultant map should look somewhat like the one shown in Figure 3.

Next, you either need to select the campus housing areas from a current layer or you need to create a new layer containing an object at the locations of interest.

For either of these options the first step is to set the map and distance units of the view. To do this, make sure the View (or map) Window is active, then choose View from the menubar and Properties from the menu. A dialog titled "View Properties" will appear, shown in Figure 9. Note the Map Units and the Distance Units selection boxes.

Figure 9. View Properties Initial Appearance

Change the Map Units to decimal degrees and the Distance Units to Miles, as shown in Figure 10.

Figure 10. View Properties Changed Appearance

Additionally, it would be useful to zoom-in more to facilitate selection of features.

To use a current layer for identifying the campus housing areas, there are two options: using the crash layers if a crash has happened at the areas of interest or using the node layer because each area should have nodes surrounding it. To use the crash layers to define the campus housing areas, use the box selection tool () to select the crashes that occurred immediately around the areas. To use the node layer to define the campus housing areas, first activate the node theme (named "Co. 85 Nodes") by moving the mouse pointer to the node theme on the left of the map, click on it. Then, make the the node theme visible by clicking on the small box to the left of the node themes name. A check mark should appear in the small box and yellow dots should appear on the map. Then, use the box selection tool () to select the nodes surrounding the campus housing areas.

To create a new layer with objects that define the campus housing areas, first select View from the menubar then New Theme from the menu. A dialog box, shown in Figure 11, will appear, asking you to identify the type of features contained in the theme. Select polygon and click on the OK button.



Figure 11. Feature Type Selection Box

Next a dialog box, shown in Figure 12, will appear asking you what you wish to call the new theme and where you want to save it. Unless you have a preference, just use the defaults and click the OK button.



Figure 12. File Name Specification Box

Once you click OK, a new theme will appear and it will be active, visible, and editable. To place a polygon at the points of interest, select the draw rectangle tool button (). Then move the crosshairs to a corner of one of the campus housing areas, click and hold the left mouse button, drag the mouse to the opposite corner of the housing area, and release the mouse button. A new polygon should appear, as shown in Figure 13.



Figure 13. New Theme Polygon Placement

Place the other polygons similarly, as shown in Figure 14.



Figure 14. Campus Housing Polygon Placement

To select the polygons, use the box selection () to select the polygons you just created. To select multiple polygons, you must hold down the shift key as you select the polygons. Your view should now look like that shown in Figure 15.



Figure 15. Campus Housing Polygon Selection

Once you have set the map and distance units and used one of these three methods to identify the intersection of interest, we can proceed with capturing those crashes within 1/4 mile of the intersection. To proceed, first make sure the crash layers for the years you are interested in are active. If not, activate them by clicking on one of them, holding down the shift key, and clicking on the others. Next, choose Theme from the menubar and Select By Theme from the menu. A dialog box will appear, shown in Figure 16.



Figure 16. Select By Theme Dialog Box Initially

Within this box, pick the theme from which you've identified the intersection (in this case the creation of a new theme option, i.e, theme3.shp). Then, under the heading "Select features of active themes that", choose "Are Within Distance Of" and insert ".25" in the box under the heading "Selection distance:" which will appear. This is displayed in Figure 15. Then click the New Set button.



Figure 17. Select By Theme Dialog Box Set for Selection

The results of the selection are shown in Figure 18.



Figure 18. Selection View

In order to see the crashes more clearly, you may want to remove the polygons you created from the view. To do this, click the left mouse button while the mouse pointer is on the check mark left of the Theme3.shp. The check mark should disappear and the screen should redraw with no polygons visible, as shown in figure 19.



Figure 19. Selection View without Polygons

You can then either "pan" the view to see the selection or you can zoom to the selection. To pan, use the panning tool () to move the map appropriately. To do this, select the tool, move the mouse pointer to the map, click and hold the left mouse button, slide the mouse pointer in the appropriate direction for the distance desired, then release the mouse button. To zoom to the selection, choose View from the menubar then choose Zoom to Selected from the menu.

You can get the total number of crashes selected by this process by choosing Request from the menubar and Crash Locations from the menu. Answers will appear as before.

Additionally, you may select multiple polygons simultaneously, create multiple polygons within the new theme and select all of them, or use other existing coverages (such as signalized intersection locations, downtown areas, tavern locations) for your selection set.

• Select Your Own
  

  Share your spatial query uses.
  

• Mapping of Selected Characteristics
  
  • Enforcement Task - pin maps of alcohol-related crashes
    

• Thematic Mapping
  
  • Enforcement
    
    • exceeding speed limit
      

    • drunk driving hotspots
      

• Select Your Own
  

  Share your mapping uses.
  

• integration with road data
  
  • Enforcement Task - crashes by speed limits
    

• integration with other data
  
  • Enforcement Task - tavern locations