Querying Data Layers

Examining Data

Important Note: This exercise should be performed using the Base Layers ArcView 8.x map document (MXD), which is available by download in the Map Gallery.

Identify Features: Identifying features in ArcView 8.x is easy. For this example, start by opening your Base Layers map document inside of ArcMap®, an application component of ArcView 8.x, and then use the Zoom In tool on the Tools toolbar to zoom into Friday Harbor. Now click the Identify tool on the Tools toolbar. Use the pointer to click on any stretch of shoreline around the city of Friday Harbor. An Identify Results box will pop up after selecting your stretch of shoreline. Examine the results to determine what type of shore you selected. (Hint: Look at the Value for the REP_NAME field.) You have successfully identified a feature using the Identify tool. Close the Identify Results box.

Find Features: If you are familiar with your data and know exactly what you are looking for, it is often resourceful to use ArcMap's Find tool to locate features quickly. For example, use the Find tool to locate all mud flats within the Northern Puget Sound Ecological Characterization (NPSEC) project area.

Select the Find tool on the Tools toolbar. In the Find dialog box, make sure the Features tab is selected and then type mud flat. In the In Layers window, choose Shoreline from the drop-down menu. Make sure the box entitled Find features that are similar to or contain the search string is checked. Under the Search option, check In fields, and under the drop-down menu select REP_NAME; which is the field representing shoreline type. Click Find.

Notice that 131 new objects were found. Each object represents a section of shoreline within the NPSEC project boundary that is considered to be the type Mud Flat. Now, click once on the first object with value Mud Flat. Right-click on this object and select Zoom to feature(s). Move the Find dialog box to the uppermost left hand portion of your screen. Right-click once on the same object you zoomed in to and select Flash feature. This will temporarily highlight the feature you are zoomed in to. Close the Find dialog box.

Measure Distances: Measuring distances between features displayed within ArcMap is also an easy task. Start by clicking on the Full Extent button on the Tools toolbar. This will show you the full extent of all your data layers. Now select the Measure tool on the Tools toolbar. You will now use the Measure tool to determine the distance between Friday Harbor and the City of Bellingham. Click once on the dot representing Friday Harbor and then move the mouse and Measure tool over to the City of Bellingham. Double-click on the dot representing the city.

The distance you just measured can be found in the bottom-left-hand corner of your ArcMap window. You should have a value of approximately 30 miles. If you would like to change your distance units from miles you can do so by changing the display units. To do this, right-click once on the data frame entitled Reptiles and then choose Properties at the bottom of the menu. Make sure the General tab is selected and change your display units to meters.

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Selecting Data

Important Note: This exercise should be performed using the Base Layers ArcView 8.x map document (MXD), which is available by download in the Map Gallery.

Select by Attribute: It is possible to select features based on attribute information by using the Select By Attributes option in ArcMap. As an example, open your Base Layers map document in ArcMap and select all man-made and rock cliff shoreline types from the Shoreline layer. To do this, click the Selection > Select By Attributes option from ArcMap's main menu.

In the Select By Attributes dialog box, select Shoreline as your layer and Create a new selection as your method. You will now create a Standard Query Language (SQL) expression that tells ArcMap what attribute field you want to query and from that which shoreline type(s) you want to query.

Create your SQL by first double-clicking REP_NAME under the Fields window, as this is the attribute field containing the names of the different shoreline types. Now click on the equal sign and then double-click on Man-made under the Unique sample values window.

So far you have created an expression that will select all features (shoreline segments) from the attribute field REP_NAME that contain the name Man-made. Remember, you also want to select all shoreline of the type Rock cliff. Therefore, continue your SQL expression by clicking the Or sign and then double-clicking REP_NAME. Now click the equal sign and then double-click Rock cliff under the Unique sample values window. Your SQL expression is complete. Your query settings should match the image below.

To make sure you entered the expression correctly, click the Verify button at the bottom of the dialog box. A message box should pop up that says The expression was executed successfully. Click OK and then click the Apply button at the bottom of the Select By Attributes dialog box. Your selection should now be highlighted in blue. Close the dialog box and view the extent of your selection. Notice that much of the shoreline within the NPSEC project area is either man-made or rocky cliffs.

Select by Location: This type of selection method allows you to select features based on their location relative to other features. In this example you will select all roads that intersect streams. Start by clearing any selections, Selection > Clear Selected Features. Now you need to make sure the Roads and Streams layers are turned on. You can do this by clicking the small box next to each layer's name in the table of contents. You are now ready to make your selection. Go to Selection > Select by Location.

In the Select By Location dialog box, you should select features from the Roads layer that intersect the features in the Streams layer. Make sure you do not apply a buffer to the Streams layer. Your selection settings should match the image below.

Now click the Apply button to select all roads that intersect streams. Close the Select By Location dialog box. Turn off the Streams layer so that you can see the new selection more clearly. With the Roads layer on, you should now notice your selection highlighted in blue. Your selection represents all roads that intersect one or more streams, and it should look similar to the image below.

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