Instructor: Welcome back to Module 1.
In Lecture 2, we'll examine feature creation
and editing in ArcGIS.
In our previous work,
we created new feature classes as the outputs
of a geo processing task, like a clip or a buffer.
Suppose instead, you want to create feature class
from scratch, a blank container
that you'll populate with features.
There are two approaches available to you in ArcGIS.
Either way, you'll arrive at the same endpoint,
a new feature class.
You can launch the create feature class wizard
from a geo database.
Right click the geo database, select new and feature class
from the list of options.
That's what we see over in the image on the left.
Alternatively, you can search
the geo processing tool library
for the create feature class tool.
Let's take a closer look at both approaches.
The first of these employs a wizard to help you out.
The wizard leads you step-by-step
through the feature class creation process.
The first step asks you to specify a dataset name
and optionally an alias as well.
Next, specify the geometry point, line,
or polygon of the dataset.
In this case, we'll select polygon
since we want to eventually digitize building footprints
on the capital campus in Montpelier.
You have the option
to set additional geometric properties here too.
The M value stores information about routes
and the Z value stores information about 3D data.
We won't use either of those here.
Lastly, you have the option
to add your output data set to the current map.
The next step is where you can specify additional attributes
and their data types.
Note that ArcGIS already includes the object ID
and shape attributes by default.
You can of course modify your table structure later
if you don't have your field definition specified
at this point.
I added a new attribute here named infrastructure type
as a text field.
Next, choose your spatial reference.
In this case, I'm going to use information
from one of the existing map layers,
NAD 83 Vermont State Plane Meters.
Then specify the dataset tolerance
or leave the default values in place.
The tolerance is used when evaluating
the spatial relationships between coordinates
and whether to consider them equal.
If you know something about the resolution of the dataset,
you can specify that here or once again,
accept the default values.
Lastly, if you'd like to specify something
other than the default configuration keyword,
this is the place to do so.
Then click finish
to complete the create feature class process.
Once you're comfortable
with the overall feature creation process,
the second approach seen here is a solid alternative
to employing the wizard.
You're still specifying the same information
for the most part.
One notable difference
is that you cannot add new attributes interactively
like you could with the wizard.
Instead, you could use a template dataset
to provide the definition of the attribute table,
just the fields, not the data.
Regardless of your approach,
you will end up with a new feature class.
One more item I'd like to talk about before we move on
is the concept of a feature dataset.
We touched on this briefly in the introduction course.
It will make use of feature datasets
throughout the advanced course.
A feature dataset is a collection
of related feature classes.
Unlike a feature class that can only have a single geometry,
a feature dataset can include point,
line and polygon feature classes.
All the feature classes within a feature dataset
share a common coordinate system.
Lastly, feature datasets can be used
to create controller datasets like a topology dataset,
which we'll talk about here in a minute.
So create a feature dataset,
add one or more feature classes to the feature dataset,
and then optionally create
one or more controllers if desired.
From the create feature dataset geo processing tool,
we see that ArcGIS is asking for three parameters,
the output geo database,
the name of the feature dataset you want to create,
and the coordinate system of the feature dataset.
I've expanded the coordinate system dropdown menu
to look at the list of possible options
for the coordinate system definition.
We see the list of dataset included in the current map pane.
You could also click the globe
on the right side of the interface
if you want to specify a coordinate system not included
in the list of options.
We'll select NAD 83 State Plain Vermont
as the coordinate system
for our capital campus assets feature dataset
and then click run.
If I look at my geo database again,
I now see a new feature dataset named Capital Campus Assets.
There are no feature classes or controller datasets included
in the newly created feature dataset.
Either drag and drop a feature class within the geo database
or import/export feature classes
or shape files from an external source
into that feature dataset.
You could also choose to create a new feature class
just like we did in the first couple slides
and store that new feature class within the feature dataset.
The image on the left displays the lab one geo database
before adding the building's feature class
while the image on the right
displays the lab one geo database
after adding the building's feature class
to the capital campus assets feature data set.
Step three is to create a controller data set.
This step is optional.
Sometimes the only benefit you're looking for
out of a feature data set
is data organization within a complex geo database design.
Let's create a topology controller as an example
of what can be done here to help
in the data development process.
What can topology do for us?
Topology defines the spatial relationships
between or among features in one or more data sets.
From a spatial analysis perspective,
topology can manage the shared geometry
between or among features,
define and enforce data integrity rules,
and help identify and correct digitizing errors.
So for example, you can use topology to ensure
that two polygons do not overlap.
Think here about creating parcel data
and the trouble that would arise if two different owners
make a claim to the same piece of land.
Right clicking the capital campus assets feature data set
and selecting new topology
from the list of options opens the Create Topology Wizard.
Since there's only one feature class in our feature dataset,
that is the only option in the list of feature classes.
I'll click the checkbox
to include it in my topology rule set.
ArcGIS assigns a topology name by default
by appending the word topology
to the end of the feature dataset name.
You can change this if you'd like.
Next, let's look at the rule creation process.
Click the add icon to add a new rule,
then choose buildings from the list of feature classes
and set the rule to must not overlap.
This ensures that if new features are added
to the building's feature class,
they cannot overlap one another.
Click next once again to arrive
to the summary of the topology definition.
Review the contents before clicking finish
to complete the process.
If we look again at the lab one geo database
and expand the contents
of the capital campus assets feature dataset,
we now see the topology controller we just created
in addition to the building's feature class
we added earlier.
Let's use the topology
to validate a data set we're working on
as part of our capital campus inventory.
The image on this slide shows a blue polygon
denoting our area of interest,
a portion of the capital campus in Montpelier.
If we navigate to the edit ribbons manage edit section,
we see there's no topology specified from my project.
The dropdown list
displays the list of available topology options.
I don't see the one that I just created,
but that's the one I want to use.
Let's fix that by adding some data to the project.
After adding the buildings feature class to my project,
I now see an additional option
in the topology dropdown menu.
The topology controller we just created,
seems like progress to me.
After selecting capital campus assets topology
from the list of options, click the error inspector button
to open the error inspector interface.
Notice the message indicating the need for more information.
In this case, a map that contains the error layers.
This terminology is a bit confusing here,
but basically what ArcGIS is asking for
is the topology controller to be added to the project.
Let's do that the same way we add a feature class
to a project, drag and drop it into the map pane.
Once that's been added, you might be in
for a little bit of a surprise.
Closer inspection of the capital campus assets topology
reveals four different items:
Dirty areas, plus point, line, and polygon errors.
Since we're working with a polygon data set,
we should only concern ourselves with the polygon errors.
The dirty area denotes potential problems in the data.
Let's return to the error inspector one more time.
Looks good this time around.
Click the validate button to check your data for errors.
Fortunately, I didn't find any problems, but at this point,
there are just those two building polygons
and they're very clearly distinct from one another.
Be sure to click the save button
after you validate your data
because ArcGIS has made changes to the topology data set,
noting that in this case there are no topology errors.
Suppose I digitize a new building footprint
in the study area that overlaps
one of the existing building footprints.
You see, I've drawn a triangular shaped footprint
that most definitely overlaps
with one of the existing buildings.
If we go back into the error inspector
and validate the data, we notice a couple of things.
The topology rule identified an error
and the error inspector provides us with a zoomed in view
of the error itself.
In this case, there's just a single error,
but if there are multiple errors,
they'd all be listed here each with its own preview.
If we look at the details, we see that the rule
that's been violated is that the buildings must not overlap.
They clearly do, and that area of overlap is identified
by the red polygon we see above.
There are three possible solutions to this error.
I could create a new feature of the problem area
distinct from the other two polygons.
In this case, we'd end up with three polygons representing
the two building footprints.
Not a good solution as far as I can tell.
I could also choose to remove the overlap.
That would delete the polygon from the dataset,
which would produce a gap in the building footprints,
also not an ideal solution.
The best option here is to merge the problem polygon
with one of the other two of polygons it is adjacent to.
Click the merge icon and a new window appears,
listing the potential merge candidates
for the offending region.
You can click an item in the list
so that you can identify it as it flashes in the map pane.
I'm going to merge the problem area into building two,
the actual capital building itself,
and leave the rest of the triangle as a new polygon.
I make my choice, the merge happens,
and now there are no longer any errors listed
in the error inspector pane.
If I click validate again,
we confirm that no errors are present.
Click save and note that all dirty areas
have been cleaned up.
Lots more to explore here, but I'll stop there for now.
You'll get some practice creating feature classes
and features during your lab exercise,
and while this is valuable to learn,
you'll also appreciate the limited amount
of digitizing required to complete your assignment.