110
Chapter 5 Working With Digital Spatial Data and GIS
necessary data. Similarly, a textbook that costs $100 is twice as expensive
as a textbook that costs $50 (as we divide the two numbers). Ratio data is
used when comparing multiple sets of numbers and looking for distinctions
between them. For instance, when mapping the locations of car wash centers,
the data associated with the location is the number of cars that use the service. By comparing the values, we can see how much one car wash outsells the
others, or calculate the profit generated by each location.
Each layer in the GIS has an associated attribute table that stores additional information about the features making up that layer. The attribute table
is like a spreadsheet where each object is stored as a record (a row) and the
information associated with the records—the attributes—is stored as fields
(columns). See Figure 5.8 for an example of an attribute table in conjunction with its GIS objects. To use the housing example again, the houses attribute table would consists of five records, each representing a house polygon.
New fields could be created, having headings such as “Owner” and “Appraised
Value” so that this type of descriptive, non-spatial data could be added for
each of the records. These new attributes can be one of the four data types (for
instance, “Owner” would be nominal data, while “Appraised Value” would be
ratio data). In this way, non-spatial data is associated with a spatial location.
attribute table a
spreadsheet-style form
where the rows consist
of individual objects
and the columns
are the attributes
associated with those
objects.
records the rows of an
attribute table.
fields the columns of
an attribute table.
FIGURE 5.8 The
attribute table associated
with a GIS data layer.
(Source: Esri® ArcGIS ArcMap
ArcView graphical user
interface Copyright © Esri.)
Fields
Records
Chapter 5 Working With Digital Spatial Data and GIS
necessary data. Similarly, a textbook that costs $100 is twice as expensive
as a textbook that costs $50 (as we divide the two numbers). Ratio data is
used when comparing multiple sets of numbers and looking for distinctions
between them. For instance, when mapping the locations of car wash centers,
the data associated with the location is the number of cars that use the service. By comparing the values, we can see how much one car wash outsells the
others, or calculate the profit generated by each location.
Each layer in the GIS has an associated attribute table that stores additional information about the features making up that layer. The attribute table
is like a spreadsheet where each object is stored as a record (a row) and the
information associated with the records—the attributes—is stored as fields
(columns). See Figure 5.8 for an example of an attribute table in conjunction with its GIS objects. To use the housing example again, the houses attribute table would consists of five records, each representing a house polygon.
New fields could be created, having headings such as “Owner” and “Appraised
Value” so that this type of descriptive, non-spatial data could be added for
each of the records. These new attributes can be one of the four data types (for
instance, “Owner” would be nominal data, while “Appraised Value” would be
ratio data). In this way, non-spatial data is associated with a spatial location.
attribute table a
spreadsheet-style form
where the rows consist
of individual objects
and the columns
are the attributes
associated with those
objects.
records the rows of an
attribute table.
fields the columns of
an attribute table.
FIGURE 5.8 The
attribute table associated
with a GIS data layer.
(Source: Esri® ArcGIS ArcMap
ArcView graphical user
interface Copyright © Esri.)
Fields
Records