Attribute Editing & Topology

Attribute editing

is the process of adding, modifying, deleting, or correcting descriptive information associated with geographic features in a GIS.

Attribute data

describes the characteristics of a geographic feature rather than its location or shape.

attribute table;

record;

field;

value

An ___ stores the descriptive information associated with the features in a GIS layer.

Each ___ in an attribute table generally represents one geographic feature.

Each ___ represents a specific type of attribute information.

Each ___ is the actual information stored in a field for a particular feature.

Adding an attribute

means entering information for a feature that previously had no value.

Updating an attribute

means changing an existing value to correct or improve the information.

Deleting an attribute value

means removing incorrect or unnecessary information from a field.

Adding a field

creates a new column in the attribute table for storing additional information.

Deleting a field

removes an attribute column from the dataset.

Field data type

determines what kind of information can be stored in a field.

text, integer, decimal, date, and Boolean values

Common field data types include

text field

stores words or characters.

integer field

stores whole numbers.

decimal field

stores numbers that contain decimal values.

Attribute consistency

means that similar features use the same format and terminology.

Attribute validation

checks whether attribute values follow the required rules or standards.

Null value

indicates that no value has been recorded for a particular attribute.

Topology

refers to the spatial relationships between geographic features.

connectivity, adjacency, and containment

Basic topological relationships include

Connectivity

describes whether features such as roads, rivers, or utility lines properly connect.

Adjacency

describes whether features correctly share boundaries.

Containment

describes whether one feature is correctly located within another feature.

topology rule

defines a spatial condition that geographic features must satisfy.

Must Not Overlap

means that features of the same layer should not occupy the same area when overlapping is not allowed.

Must Not Have Gaps

means that polygons that are supposed to completely cover an area should not contain unintended empty spaces.

Must Be Covered By

means that a feature must be completely contained within another specified feature.

Must Be Inside

means that a feature must occur within the boundary of another feature.

Must Not Have Dangles

means that line features should not have unnecessary endpoints where they are expected to connect.

Must Not Intersect

means that features should not cross each other when their intersection is not allowed.

Must Be Covered By Boundary Of

requires a feature to lie along the boundary of another feature.

Overlap error

occurs when two features occupy the same area when they should not.

Gap error

occurs when an unintended empty space exists between adjacent polygons.

Dangle error

occurs when a line ends without properly connecting to another line.

Overshoot

occurs when a line extends beyond the location where it should end.

Undershoot

occurs when a line stops before reaching the feature it should connect to.

Sliver polygon

is a small, narrow polygon created unintentionally by mismatched boundaries.

Self-intersection

occurs when a feature crosses itself in an invalid or unintended manner.

Attribute editing

ensures that the descriptive information of a feature is correct.

Topology checking

ensures that the spatial relationships and geometry of features are correct.

Data quality

refers to how accurately, completely, consistently, and reliably a GIS dataset represents the real-world features it describes.

Completeness

refers to whether all required features and attributes have been included.

Consistency

refers to whether data follows the same standards throughout the dataset.

Accuracy

refers to how closely the data represents the actual geographic feature or attribute.