· web view1 lab 4a: creating and editing feature classes so far, we’ve mostly focused on...

Winter 2014 ArcGIS for Geoscientists GEOL 596

Lab 4a: Creating and editing feature classes

So far, we’ve mostly focused on importing data into ArcGIS rather than creating or digitizing data within ArcGIS.

Editing is one of the reasons to group all of your files into a single geodatabase. By doing so, and having everything in the same projection to begin with, you can edit all of the layers at the same time. A little organization ahead of time can go a long way, in this case, making it relatively easy to move between layers and make changes.

This lab will cover the basics of creating and editing feature classes in the following sections:

Creating a line feature class for faults and contacts p. 2o Creating a point feature class end of p. 3

Creating new features in a feature class p. 4o Adding new fields to your attribute table end of p. 7

Adding symbology to make templates p. 8

The ArcGIS Desktop Help sections are extensive, and you will likely consult those frequently as you get more advanced. Editing is also an iterative process, and you will find yourself going back and forth between different types of editing quite a bit.

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Creating a line feature class for faults and contactsTo make a geologic map, one of the main things you need is a line feature class in which to put all of your faults and contacts. It might seem counterintuitive to put these all on one layer, but you will use this line layer to generate the colored polygons that indicate the rock type, so this is the easiest way to go about it.

1. In the Catalog tree, right-click the feature datset in which you want to create a new feature class. Select New Feature Class.

2. Type faults_and_contacts as the name for the feature class (see Naming Rules, below). You can also provide an alias, which is the name that you will see when you add the feature class to a project in ArcMap. Naming rules do not apply here, so it can be a way to provide a bit more readable description (like Faults and Contacts).

Naming rules Names must begin with a letter, not a number or special character such as an

asterisk (*) or percent sign (%). Names cannot contain spaces. If you have a two-part name for your table or

feature class, connect the words with an underscore (_), for example, garbage_routes.

Names should not contain operational words, such as select or add. The length of feature class and table names depends on the underlying database.

The maximum name length for file geodatabase feature classes is 160 characters.

3. Choose Lines from the drop-down list the type of features that will be stored in this feature class. You don’t require m- or z-values, so click Next.

4. Leave the default selection of the keyword configuration and click Next.5. Now you are at a table where you can define the fields that are part of this feature class.

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Fields are like column headings in a spreadsheet, and the data type is like the column type. ArcGIS includes some fields automatically, including the ObjectID (a unique numeric identifier for each feature) and Shape. For each field you want to add, you enter a name for that field (naming rules apply) and the type of data that will be in that field.

Add the following fields to your feature class:

Field Name Data TypeLine_type TextCertainty TextName TextNotes Text

The field names and data types determine how you are able to apply symbols to your lines. So for example, in your line_type field, you will enter things like normal fault or contact or map boundary. In the Certainty field, you will enter things like certain or inferred or buried. Then you can apply different symbologies to those features based on what you’ve entered: you can faults thicker than contacts, make inferred faults and contacts dashed, etc. (The mechanics of that come later.)If you have an existing feature class or template that you want to import the field from, you can do that here, too, using the import data. This does NOT import the data from that other feature class – just the fields. (So, for example, if you made a fault layer for a different map and you liked all of the fields in that feature class, you can just import it.)

6. Click Finish – and you see your new feature class. There is no data in it yet, of course, but we’ll get there.

Creating a point feature classThe steps are exactly the same as described above, but you will choose points instead of lines when you create the feature class. You can define whatever you want for the fields.

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Creating new features in a feature classWithin ArcMap, when you simply add layers or add data, you are not immediately able to change or edit these layers. In order to be able to edit, you have to turn on editing, or start an editing session.

1. Launch ArcMap and open whatever map you’ve been working on. 2. Add the feature class that you just created by using the same Add data process.3. If you haven’t used it before, you will need to add the Editor toolbar (there are lots of

times you need to add a toolbar). There are a couple of ways to do this:

a. Either click the Editor Toolbar button on the Standard toolbar to display the Editor toolbar.

b. Or go to Customize Toolbars Editor (this way you can see just how many toolbars there are available to you).

This opens the toolbar as a separate window. You can then drag it up into the toolbar region to dock it so that it is always there when you open ArcMap.

4. Now you can start an editing session. There are also two ways to do this. You can:a. Either right-click on the layer you want to edit and select Edit features Start

Editing

b. Or click on Editor in the editing toolbar and select Start Editing.

If your data frame contains layers from multiple geodatabases or workspaces, you will be confronted with a dialogue box asking you which layer(s) you want to edit. In

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this case, select the layer you want to edit and click OK. If you don’t receive a dialogue box, it’s because all of the layers in your data frame are in the same geodatabase or folder.

5. This should open the Create Features window on the right side of your ArcMap window. You might think you are now ready to start creating features – but not quite yet. If this is the first time you’ve started editing this layer and want to create new features, the next thing you need to do is create templates for the kinds of features that you will create.

Rather non-intuitively, you need to select the Organize templates icon in order to create a new template (see above). When this window opens, you will see your layer name with a line next to it:

Here’s the next very non-intuitive thing: you don’t actually need to click New Template to make a new template – ArcMap has already done this for you. But you might want to… but let’s not do that yet. Instead, click on Properties. When this box opens, you should see all of the attribute fields for your feature class, the default symbol (a line), etc. If this is a totally new layer for you with no features in it yet, as is likely, then you may not need to change anything here. Eventually, however, imagine that you have a line feature class in which you are putting faults and contacts. You might make two templates for two types of features in this single layer: one template for faults, and one for contacts, and you could choose the symbology accordingly. For now, however, go ahead and click OK in the Properties dialogue box, and close out of the Organize Templates dialogue box.

6. Now you are almost ready to create new features. The other thing you want to make sure is that you have turned on snapping: this means that your line segments will snap to each other and connect when you want them to. In the Editing toolbar, select Editor

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Snapping Snapping Toolbar. This will bring up the Snapping toolbar, which you can also add to your dock.

Click on Snapping with the down arrow next to it, and make sure that Use Snapping has a check mark next to it. You can then decide which things you want to snap to. You can also select Snapping Options… and look at the things you can manipulate – in particular, the snapping “tolerance”, or how far away from another point the snapping will kick in. This is something you can play around with and determine how picky you want to be. You don’t want this tolerance to be too high, or things will snap together that you want to remain separate. Turning on snapping now can save you a lot of time and effort in the future when you want to create polygons from your mapping.

7. Now you are ready to create some new line features. You should have your template selected in the Create Features window, and several tools should be available to you in the Editor toolbar:

For now, starting with the straight line segment tool, which is selected in the image above. When you hover over your map, you should see a cross-hairs. Left-click to create a vertex, and just keep clicking along to create a new line feature – something Arc at this point calls an “edit sketch”. You will be able to edit these vertices, so don’t worry if they aren’t perfect. You can double-click when you are ready to end the sketch, or you can right-click on your final point and select Finish Sketch.

Very important note Your new features and edits are not automatically saved, nor are they saved when you save the map document. You specifically have to save your map edits, which you do through the Editing toolbar (Editor Save edits). Do this frequently. Very frequently. Get in the habit. Period.

8. Now you want to define the attributes for this feature. In the Editing toolbar, select the Selection Arrow . Select your line feature by left-clicking on it, and then right-click on the selected feature. Select Attributes. This will open the Attribute table for that feature in your right menu, where you can fill in all of the fields by typing them in. It’s best to do this as you go, though you can continue to edit later. (You can also open the attribute table by clicking on the Attribute Table icon in the Editing toolbar ).

9. Save your edits. 10. Let’s assume you didn’t do a perfect job on your line and vertex placement. You have

lots of options for editing existing features, some of which are similar to graphics programs and others of which are not so similar. With the Selection tool, again right-click on your line and select Edit Vertices. The edit vertices toolbar should pop open when you do this, and all of your vertices will reappear for you to edit.

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The default selection of the arrow allows you to move vertices around – you can hover over the others to see what they allow you to do (add, remove, etc.).

11. The other tool I use fairly frequently when making maps is the Split Line tool . I use it to draw an entire fault or contact conceptually, and then split it into segments that are exposed, inferred, or concealed. To use this tool, you need to select the line first, then select the split tool and click on the line where you want to split it.

12. Save your edits. Those are the basics of creating and editing line features, which are the most commonly created and edited, at least in our world. All of the same principles apply when creating and editing points or polygons. The rest of this lab is really just you working on creating and editing your own features.

Adding fields to your attribute tableAfter you’ve been doing some editing, you may find you need to add fields to your attribute table or edit existing fields. You have to do this through Arc Toolbox, and you cannot be editing the feature class at the same time (you might not be able to have ArcMap open at all). You can add these at any time, and fill in the attributes in a variety of ways – through the table, or through selecting one feature at a time.

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Defining symbology and layer properties to make new templatesIf you have a faults and contacts feature class, you can make multiple templates for creating new features, and then these features can automatically take on the symbology assigned to those templates – this requires a little advanced planning and the use of the Layer Properties dialogue, but is not difficult. You can do this even if you have an empty feature class.

1. Right-click on your layer and open the Properties dialogue.2. Select the Symbology tab, and select Categories Unique values in the left-hand menu,

as you’ve done before.

3. Make sure the correct value field is selected for what you want to base the symbols on – if you have a faults and contacts layer, this will likely be something like “Line_type”, and then click on Add Values… .

4. In the dialogue that opens, add the values that you will enter for the features using the Add to List box, such as Contact, concealed (see below for an example). Enter them one at a time, and click OK when you are done.

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Now, back in the symbology tab of the layer properties dialogue box, you can define the symbology for each of these features as you did for points in the last lab. Again, you can use the Geology 24K style sheet as a guide, but I find I need to make adjustments. One of those is adding symbols to faults (e.g. balls on normal faults, triangles on thrust faults), so I will go through that process here. Because I mostly work with normal faults, that’s the symbol I will help you make, but the process is exactly the same for other types of faults.

5. Right-click on your Normal fault symbol and select Properties for Selected Symbol(s)…

6. In the Symbol dialogue box, select a black line that is 1.5 pixels wide, then click on Edit Symbol.

What you want to do here is add a layer to the symbol that has the balls in it, so click on the big plus sign under the layers window in the left side of the dialogue box. This should add a layer, likely as another simple line.

7. Select your new layer, and make sure the padlock symbol next to it is clicked open. Then you want to change the type – you want this layer to be a Marker Line Symbol.

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Notice that when you make this selection, you now have several tabs where you can modify features. First you want to choose a symbol, so click on the Symbol box in the Marker Line tab. Choose a black circle, perhaps sized down to 10 pts.

8. Now click on the Template tab – this is where you can set the spacing of the circles. Play around with the location and spacing of the black squares until you get a spacing that you like. You probably don’t want a symbol right at the very end of the line, so you will want to move that one, too.

9. Now click on the Line Properties tab. Here is where you define the offset of the symbol from the line. If you leave the offset at 0, the balls will appear directly over the line, but you want them off to one side. You can play around with this until you get what you need.

10. Click OK to get back to the Symbol Selector window, then OK to return to the Layer Properties dialogue box.

11. You can continue to go through that process for as many of the feature types as you want. You can then use this symbology to create new templates for making features, or you can apply the symbology later.

Note This means that your lines have a direction to them. If you go into ArcMap and apply your symbology and the balls show up on the wrong side, do not fret! With editing turned on, you will select the feature, and select Edit Vertices. Then right-click on the feature and select Flip. And all will be well.

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· web view1 lab 4a: creating and editing feature classes so far, we’ve mostly focused on...

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