Gis vector editing tool use case

The left graphic below shows the polygon feature being constructed from an edit sketch. Once all the desired vertices are added, the sketch is finished and becomes a feature. You can double-click a feature with the Edit tool to modify the sketch, thereby changing the shape of the polygon.

To create a new line, at least two vertices—the start and end points—are required to finish the sketch, and therefore, create the feature. To create a new polygon with the Polygon tool, for example, at least three vertices are required.

A sketch of a line records the direction it was digitized, which is important if you need to trim or extend the line or perform an operation on it that uses measurements originating from the start or end point. Vertices are marked in green, with the last vertex added marked in red. You can change the colors of the edit sketch on the Editing Options dialog box. To enhance productivity, the construction methods palette is also found on the Feature Construction mini toolbar, which appears near your pointer when you are digitizing segments in new lines or polygons.

The Feature Construction toolbar is turned off by default, but you can press the TAB key to display it temporarily or enable it on the Editing Options dialog box so it appears any time you are sketching. In addition, there are many keyboard shortcuts available, and you can right-click the map to access a shortcut context menu containing commands for the precise placement of vertices. For example, you can add a vertex at a specific x,y location; draw a segment at an exact length and direction; or make a segment parallel or perpendicular to another segment.

In addition to the Line and Polygon tools, other tools are available to create lines and polygons. The Circle and Rectangle tools allow you to create circles and rectangles by dragging the mouse interactively, or at precise locations with keyboard shortcuts. The Ellipse tool allows you to create a new ellipse feature interactively or by using shortcuts to specify the location and major or minor radii.

When creating polygons, you can also choose the Auto-Complete Polygon tool, which is used to create adjacent polygons that do not overlap or have gaps. You can store map text as annotation in a geodatabase. Annotation provides flexibility in the appearance and placement of your text because you can select individual pieces of text and edit them. Dimension features are a form of annotation designed to express distance measurements.

Like other types of features, geodatabase annotation and dimension features are created inside an edit session, using feature templates and the tools on the Create Features window. Some annotation feature classes, such as standard annotation, stand alone in the geodatabase. Standard annotation is not formally associated with features in the geodatabase.

For example, you might have a piece of standard annotation that represents a mountain range, an ocean, or an administrative boundary—the annotation simply marks the general area on the map. Another kind of annotation, feature-linked annotation, is associated with the feature it is describing through a relationship class. The text reflects the value of a field or fields from the feature to which it is linked.

You might use feature-linked annotation to identify features such as parcels, streets, rivers, roads, or cities. With feature-linked annotation, as you create parcels or street features, for example, using the editing tools in ArcMap, annotation is created automatically.

Sometimes, you may want to create features of a certain type in an existing layer, but the layer is not set up to capture those features. For example, you want to add features to a roads layer to represent an unpaved road, but you currently only have categories in your data for freeway, major highway, and local road.

Through a wizard, you can define everything about the unpaved road category at one time—making it easy to prepare your data to display and store the new types of features.

ArcMap automatically adds a symbol for the new category, any required geodatabase information such as subtype value or coded domain value for that layer, and a feature template to use when creating an unpaved road. The wizard saves you from having to stop your work to open multiple dialog boxes to set up the data on your own.

Attributes are descriptions of a geographic feature in a GIS, usually stored as a row in a table. For example, attributes of a river might include its name, length, and average depth. You can enter new attribute values when you create features, and you can edit existing values. When you create a feature, it starts with only the default attribute values as specified in the template used to create the feature.

You input attributes after you create a feature. There are two main ways of adding or updating attributes in ArcMap: the Attributes window and the table window. The Attributes window displays attributes of selected features and allows you to edit the values.

The top panel of the window shows the layer by its display expression to which the selected feature or features belong, while the bottom panel shows the attribute values of that feature—including any related or joined information.

The properties and order of fields reflect the settings on the Fields tab of the Layer Properties dialog box. Also, it is possible to store relationships, such as multi-layer topology within the geodatabase. The basic data model for feature layers point, line, polygon is used in the geodatabase model.

Vector data stored in geodatabases are referred to as feature classes or feature datasets which are groups of individual feature classes. Rasters can also be stored in geodatabases. In addition to converting shapefiles or geodatabase feature classes from other feature data sources, it is also possible to create shapefiles or feature classes from scratch, using other feature data layers or images only as a visual guide for positional reference.

For the rest of this lecture, shapefiles and feature classes will be referred to simply as "feature classes.

When a new feature class is created, the user must decide whether the feature class will represent point, line, or polygon features. You need to determine in advance what the feature type will be for your dataset. The feature class must also be given a name and a place in the file system. The coordinates of the new features are determined by the extent of the data frame to which the features are added and by the coordinate system of the new dataset. If you are using a new data frame without other layers, the features you add will be placed near the data frame's origin by default, a new data frame's extent is roughly [ 0,0 , 1,1 ].

The new layer is ready for editing, but contains no features or tabular attributes. This is similar to creating a new spreadsheet or word processed document; when it has just been created, it is empty. In order to add features to the new shapefile, it needs to be added to an ArcMap document and opened for editing. Adding shape layer features. Once the new layer is added to the map document and open for editing, you can add features. The Editor toolbar in ArcMap needs to be enabled.

Within the Editor toolbar there are a number of different tools for creating and editing features. There are also a number of different editing tasks to choose from. We will cover the most common tools and tasks, but will not have the time to cover all editing tools and tasks.

The different editing tools are on a dropdown list of icons, each of which performs a different editing function. Depending on the application's state, one or more of the tools may be unavailable grayed-out. The list of tools and their functions is listed here:. Adding attributes. When a new feature class is created, a "bare bones" attribute table is also created. This table will initially contain only a single record for each feature, and two fields, FID , Shape and Id. In the following table, one point has been created, and the attribute table is displayed.

The user can add fields to the attribute table or to any table in the project, for that matter. Fields are added to represent properties of the spatial features. When fields are added, the field name, data type e. The new field is appended after the last existing field in the table. Editing feature classes feature classes that have been created from scratch, or from other sources, can be edited. When a new feature class has been created, it will automatically be placed in edit mode.

However, any feature class can be edited, assuming the user has write permission to the files and directories on the disk that store the feature class. In order to start editing a vector layer the next steps are recommended: Select the vector you wish to edit by clicking it. Go to Toggle Editing and start a new edit session. Activate the Advanced Digitizing toolbar. The new toolbar is opened. With the trace tool activated follow the administrative unit limit. About the Author: Catalin Cimpianu.

Often, the original features will have different values for a given attribute. In this case, the first attribute encountered is carried over into the attribute table, and the remaining attributes are lost. This operation is particularly useful when polygons are found to be unintentionally overlapping. Merge will conveniently combine these features into a single entity. Among the most powerful and commonly used tools in a geographic information system GIS is the overlay of cartographic information.

In a GIS, an overlay The process of taking two or more different thematic maps of the same area and placing them on top of one another to form a new map. Inherent in this process, the overlay function combines not only the spatial features of the dataset but also the attribute information as well. How would you attack this problem?

With a GIS at your command, answering such spatial questions begins with amassing and overlaying pertinent spatial data layers. For example, you may first want to determine what areas can support the mall by accumulating information on which land parcels are for sale and which are zoned for commercial development.

After collecting and overlaying the baseline information on available development zones, you can begin to determine which areas offer the most economic opportunity by collecting regional information on average household income, population density, location of proximal shopping centers, local buying habits, and more. Next, you may want to collect information on restrictions or roadblocks to development such as the cost of land, cost to develop the land, community response to development, adequacy of transportation corridors to and from the proposed mall, tax rates, and so forth.

Indeed, simply collecting and overlaying spatial datasets provides a valuable tool for visualizing and selecting the optimal site for such a business endeavor. Several basic overlay processes are available in a GIS for vector datasets: point-in-polygon, polygon-on-point, line-on-line, line-in-polygon, polygon-on-line, and polygon-on-polygon.

As you may be able to divine from the names, one of the overlay dataset must always be a line or polygon layer, while the second may be point, line, or polygon. The point-in-polygon overlay An overlay technique that creates an output point layer that includes all the points occurring within the spatial extent of the overlay layer. Upon performing this operation, a new output point layer is returned that includes all the points that occur within the spatial extent of the overlay Figure 7.

In addition, all the points in the output layer contain their original attribute information as well as the attribute information from the overlay. For example, suppose you were tasked with determining if an endangered species residing in a national park was found primarily in a particular vegetation community.

The first step would be to acquire the point occurrence locales for the species in question, plus a polygon overlay layer showing the vegetation communities within the national park boundary. Upon performing the point-in-polygon overlay operation, a new point file is created that contains all the points that occur within the national park.

The attribute table of this output point file would also contain information about the vegetation communities being utilized by the species at the time of observation. A quick scan of this output layer and its attribute table would allow you to determine where the species was found in the park and to review the vegetation communities in which it occurred.

This process would enable park employees to make informed management decisions regarding which onsite habitats to protect to ensure continued site utilization by the species.

As its name suggests, the polygon-on-point overlay An overlay technique that creates a polygon layer from those input polygons that overlay features in a point layer. In this case, the polygon layer is the input, while the point layer is the overlay. The polygon features that overlay these points are selected and subsequently preserved in the output layer. For example, given a point dataset containing the locales of some type of crime and a polygon dataset representing city blocks, a polygon-on-point overlay operation would allow police to select the city blocks in which crimes have been known to occur and hence determine those locations where an increased police presence may be warranted.

A line-on-line overlay An overlay technique in which output from this operation is a point s located at the intersection s of the two linear datasets. The output from this operation is a point or points located precisely at the intersection s of the two linear datasets Figure 7. For example, a linear feature dataset containing railroad tracks may be overlain on linear road network.

The attribute table for this railroad crossing point dataset would contain information on both the railroad and the road over which it passed. The line-in-polygon overlay An overlay technique in which each line that has any part of its extent within the overlay polygon layer will be included in an output line layer.

In this case, each line that has any part of its extent within the overlay polygon layer will be included in the output line layer, although these lines will be truncated at the boundary of the overlay Figure 7. For example, a line-in-polygon overlay can take an input layer of interstate line segments and a polygon overlay representing city boundaries and produce a linear output layer of highway segments that fall within the city boundary.

The attribute table for the output interstate line segment will contain information on the interstate name as well as the city through which they pass. The polygon-on-line overlay An overlay technique in which polygon features that overlay lines are selected and subsequently preserved in an output layer.

In this case, the polygon layer is the input, while the line layer is the overlay. The polygon features that overlay these lines are selected and subsequently preserved in the output layer. Finally, the polygon-in-polygon overlay An overlay technique in which a polygon input and overlay layers are combined to create an output polygon layer with the extent of the overlay.