Lecture 4
Geodatabases
Geodatabases Outline
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Data types
Geodatabases
Data table joins
Spatial joins
Field calculator
Calculate geometry
ArcCatalog functions
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Lecture 4
DATA TYPES
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Directly loadable data types
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dBase (.dbf)
Text with comma (.csv) or tab-separated
values (.txt)
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Microsoft Access (.mdb)
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Microsoft Excel (.xls)
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Data table formats
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First row must have attribute names with
self-documenting labels
 (e.g. Pop5To17, Area)
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Usual naming convention
 first character is a letter
 remaining characters be any letters, digits, or the
underscore character
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All additional rows of a data table contain
attribute values
None of the rows can be sums, averages, or
other statistics of raw data rows
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Lecture 4
GEODATABASES
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Geodatabase types
Manages features and tables inside a
database management system
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File geodatabase
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stores datasets in a folder of files
each dataset file up to 1 TB in size
can be used across platforms
can be compressed and encrypted for read-only,
secure use
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Geodatabase types
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Personal geodatabase
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stores datasets in a Microsoft Access .mdb file
storage sizes between 250 and 500 MB
limited to 2GB
only supported on Windows
ArcSDE geodatabase
 stores datasets in a number of optional DBMSs:
 IBM DB2, IBM Informix , Microsoft SQL
Server , Oracle, or PostgreSQL
 unlimited size and users
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New file geodatabase
ArcCatalog
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Import into geodatabase
Shapefile features
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Import into geodatabase
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Tables
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Export from geodatabase
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View geodatabases
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Cannot identify names in Windows Explorer
Must use ArcCatalog
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Compact geodatabases
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File and personal geodatabases
 Reduces size and improves performance
 Compact personal geodatabases > 250 MB.
 Geodatabases with frequent data entry, deletion,
or general editing
 Open geodatabases in ArcMap cannot be
compacted
 remove any layers with a source table or
feature class in that database from the TOC
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Compress geodatabases
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File geodatabases
 Once compressed, a feature class or table is
read-only and cannot be edited
 Compression is ideally suited to mature datasets
that do not require further editing
 Compressed dataset can be uncompressed to
return it to its original, read-write format
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Lecture 4
DATA TABLE JOINS
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Data table joins
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Putting two tables together to make one
table
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Join two tables one-to-one by row
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Must have the same values and data types
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Join example
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Housing heating fuel study for U.S. Counties
 Source: U.S. Census
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Data table: Census SF3 table for heating fuel
by county
Map Features: County polygons
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Data table
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Heating fuel table (Excel spreadsheet)
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Data table
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Heating fuel table data dictionary
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H040001: Occupied housing units: House heating fuel; TOTAL Units
H040002: Occupied housing units: House heating fuel; Utility gas
H040003: Occupied housing units: House heating fuel; Bottled; tank; or LP gas
H040004: Occupied housing units: House heating fuel; Electricity
H040005: Occupied housing units: House heating fuel; Fuel oil; kerosene; etc.
H040006: Occupied housing units: House heating fuel; Coal or coke
H040007: Occupied housing units: House heating fuel; Wood
H040008: Occupied housing units: House heating fuel; Solar energy
H040009: Occupied housing units: House heating fuel; Other fuel
H040010: Occupied housing units: House heating fuel; No fuel used
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Feature class
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County polygons
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Add data and features to map
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Open attribute tables
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Find common attribute to join
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Data problem
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FIPS has leading zero
and is a TEXT field.
FIPS
01001
01003
01005
01007
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GEO_ID2 is a NUMBER field
with no leading zeros.
GEO_ID2
1001
1003
1005
1007
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Data solution
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Make a new NUMBER field in Counties
attribute table and use field calculator to
populate new field from old
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Data solution
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New FIPS_NUM is same as GEO_ID2 and
ready to join
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Join tables
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Join result
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Heating fuel data is now listed for every
county in the USCounties feature attribute
table
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Permanent joins
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Joins are temporary and can be removed
Export data to make joins permanent
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Choropleth map result
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Lecture 4
SPATIAL JOINS
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Spatial join example
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You have census block group centroids with
housing fuel data
You want to know housing fuel data by
neighborhoods
No attributes in common
Spatial join needed
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Spatial joins
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Points to polygons
 Spatially joins points (block centroids) within
polygons (neighborhoods)
 Joins using “shape” (not attribute field)
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Spatial joins
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Right click polygon layer (neighborhoods)
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Join result
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New polygon feature
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Join result
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Counts and sums
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Count result
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Number of points in each polygon
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Sum result
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Every block group centroid has associated data
 (e.g. H040004, heating electricity shown in labels)
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Sum result
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One neighborhood example
 Central business district
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4 block groups
Housing units with electricity fuel (80 + 299 + 128 + 292 )
Sum = 799
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Choropleth map result (sum)
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Choropleth map result (sum)
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Other spatial joins
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Polygons to points
 Example: ATM robberies (points) need
neighborhood name
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Polygon to point join result
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Neighborhood name shows on each point
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Other spatial joins
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Points to points
 Example: What is the distance of a burglary to
the nearest commercial property?
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Point to point join result
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Distance to nearest commercial property
shows on each burglary point
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Lecture 4
FIELD CALCULATOR
(as in “Feature-Attribute” Calculator)
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Sample functions
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Performs numeric calculations
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Populates field
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Concatenates text data
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Field calculator functions
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Calculate acres to square miles
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Field calculator functions
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Populate field with county name
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Field calculator functions
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Concatenate house number and street fields
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Lecture 4
CALCULATE GEOMETRY
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Polygon/point centroids
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Advanced calculations for finding a
polygon’s point centroid
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Calculate XY fields
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Add new X and Y fields in the attribute table
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Calculate XY fields
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Calculate geometry for X field, repeat for Y
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XY field results
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Results are X and Y values based on map
properties (e.g. Long/Lat or XY feet)
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Export as shapefile
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XY events should be exported as permanent
shapefile or feature class
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Lecture 4
ARCCATALOG FUNCTIONS
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Basic functions
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Copy, paste, rename, etc.
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View and edit properties
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Projections, fields, etc.
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View metadata
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Edit metadata
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Create new files
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Geodatabases, tables, features, etc.
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Summary
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Data types
Geodatabases
Data table joins
Spatial joins
Field calculator
Calculate geometry
ArcCatalog functions
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