GEG 310: Week 2

GIS Tables & Attributes

Non-spatial data

• Descriptive info that does not have location-based qualities 

• Stored in attribute tables (spreadsheet-style forms)

  • Linked to a layer 

• Stand-alone tables are possible (not linked to a layer) 

Attribute tables 

• Associated to a spatial data layer

• Store attributes of map features

• Have special fields for spatial information, like “shape” that indicate the type of object (point, line or polygon)

Standalone tables 

• Store any tabular data

• Not associated with spatial data

• Can have different formats like a CSV or an EXCEL table

Types of GIS attribute data (mid term question)

• Nominal: unique identifier of some kind (categorical),

  •  Name of person, title, phone number, sex

• Ordinal: represent a ranking 

• Interval (numeric): difference btwn #s is significant but there is no fixed non-arbitrary zero point associated w/ data 

  • Celsius, fahrenheit, elevation, time (12 hr clock)

• Ratio (numeric): difference btwn #s is significant but there is no fixed non-arbitrary zero point associated w/ data 

• True 0 point = there can be absolutely nothing 

  • population  total, crime rate

Keys to joining tables in ArcGIS

• In a Join, data from the source table are appended to the destination table

• A Join can be removed when it is no longer needed

• If a layer containing the destination table is exported to a new layer after a join, the new fields resulting from the join will be permanently saved in the new layer

•  join is considered a one-to-one join if there is a one-to-one relationship between the tables: there is only a single record from each table being joined to a single record in the other table.

• A many-to-one join is a join in which many records in an attribute table are joined to the same one record in the other table.

Selecting records in arcGIS Pro

• Records selection: using select feature 

• Select by location: select features in one or more layers based on their location in relation to features in another layer 

• Perform Queries: select by attributes 

Queries in ArcGIS

• Select a subset of features and table records 

• Simple 

  • Ask one question in relation to data 

• Compound 

  • Add multiple questions based on initial question