Page 115 - DCAP208_Management Support Systems

Management Support Systems

Notes Attribute data: Attribute data describes characteristics of the spatial features. These
characteristics can be quantitative and/or qualitative in nature. Attribute data is often
referred to as tabular data.
The coordinate location of a forestry stand would be spatial data, while the characteristics of that
forestry stand, e.g. cover group, dominant species, crown closure, height, etc., would be attribute
data. Other data types, in particular image and multimedia data, are becoming more prevalent
with changing technology. Depending on the specific content of the data, image data may be
considered either spatial, e.g. photographs, animation, movies, etc., or attribute, e.g. sound,
descriptions, narrations, etc.

Sources of Data

A wide variety of data sources exist for both spatial and attribute data. The most common
general sources for spatial data are:
Hard copy maps

Aerial photographs
Remotely-sensed imagery
Point data samples from surveys
Existing digital data files
This spatial data is usually in analog form and needs to be converted to digital form before it can
be used. Maps can be digitized, or hand traced with at computer mouse, to collect the coordinates
of features.

Attribute data has an even wider variety of data sources. Any textual or tabular data than can be
referenced to a geographic feature, e.g. a point, line, or area, can be input into a GIS.

Did u know? Attribute data is usually input by manual keying or via a bulk loading utility
of the DBMS software.

Data Editing and Quality Assurance

Data editing and verification is in response to the errors that arise during the encoding of spatial
and non-spatial data. The editing of spatial data is a time consuming, interactive process that can
take as long, if not longer, than the data input process itself. Several kinds of errors can occur
during data input. They can be classified as:

Incompleteness of the spatial data: This includes missing points, line segments, and/or
polygons.
Locational placement errors of spatial data: These types of errors usually are the result of
careless digitizing or poor quality of the original data source.
Distortion of the spatial data: This kind of error is usually caused by base maps that are
not scale-correct over the whole image, e.g. aerial photographs.

Incorrect linkages between spatial and attribute data: This type of error is commonly the
result of incorrect unique identifiers (labels) being assigned during manual key in or
digitizing. This may involve the assigning of an entirely wrong label to a feature, or more
than one label being assigned to a feature.

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