Lecture 4 Geodatabases. Geodatabases Outline Data types Geodatabases Data table joins Spatial joins Field calculator Calculate geometry

Lecture 4

Geodatabases

Geodatabases Outline Data types Geodatabases Data table joins Spatial joins Field calculator Calculate geometry ArcCatalog functions

2INF385T(28437) – Spring 2013 – Lecture 4

DATA TYPES Lecture 4


Directly loadable data types

dBase (.dbf) Text with comma (.csv) or tab-

separated values (.txt)

Microsoft Access (.mdb)

Microsoft Excel (.xls)


5

Data table formats First row must have attribute names

with self-documenting labels (e.g. Pop5To17, Area)

Usual naming convention first character is a letter remaining characters be any letters, digits,

or the underscore character 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

INF385T(28437) – Spring 2013 – Lecture 4

GEODATABASESLecture 4


8

Geodatabase typesManages features and tables inside a database management system

File geodatabase 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


9

Geodatabase types Personal geodatabase

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


10

New file geodatabase

ArcCatalog


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Import into geodatabase


Shapefile features

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Import into geodatabase

Tables


13

Export from geodatabase


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View geodatabases Cannot identify names in Windows

Explorer Must use ArcCatalog


15

Compact geodatabases

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


16

Compress geodatabases 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


DATA TABLE JOINSLecture 4


18

Data table joins Putting two tables together to make

one table

Join two tables one-to-one by row

Must have the same values and data

types


19

Join example

Housing heating fuel study for U.S.

Counties

Source: U.S. Census Data table: Census SF3 table for heating

fuel by county

Map Features: County polygons


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Data table

Heating fuel table (Excel spreadsheet)


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Data table

Heating fuel table data dictionary 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

County polygons


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Add data and features to map


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Open attribute tables Find common attribute to join


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Data problem FIPS has leading zero

and is a TEXT field.

GEO_ID2 is a NUMBER fieldwith no leading zeros.


FIPS

01001

01003

01005

01007

GEO_ID2

1001

1003

1005

1007

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Data solution 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 New FIPS_NUM is same as GEO_ID2 and

ready to join


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Join tables


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Join result Heating fuel data is now listed for

every county in the USCounties feature attribute table


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Permanent joins Joins are temporary and can be

removed Export data to make joins permanent


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Choropleth map result


SPATIAL JOINSLecture 4


33

Spatial join example 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 Points to polygons

Spatially joins points (block centroids) within polygons (neighborhoods)

Joins using “shape” (not attribute field)


35

Spatial joins Right click polygon layer

(neighborhoods)


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Join result New polygon feature


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Join result

Counts and sums


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Count result Number of points in each polygon


39

Sum result Every block group centroid has associated

data (e.g. H040004, heating electricity shown in

labels)


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Sum result


One neighborhood example Central business district

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

Polygons to points Example: ATM robberies (points) need

neighborhood name


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Polygon to point join result

Neighborhood name shows on each

point


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Other spatial joins 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 Distance to nearest commercial

property shows on each burglary point


FIELD CALCULATORLecture 4


(as in “Feature-Attribute” Calculator)

Sample functions

Performs numeric calculations

Populates field

Concatenates text data


Field calculator functions

Calculate acres to square miles


Field calculator functions

Populate field with county name

INF385T(28437) – Spring 2013 – Lecture 4 50

Field calculator functions Concatenate house number and street

fields


CALCULATE GEOMETRYLecture 4


Polygon/point centroids Advanced calculations for finding a

polygon’s point centroid


Calculate XY fields

Add new X and Y fields in the attribute

table


Calculate XY fields Calculate geometry for X field, repeat

for Y


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XY field results Results are X and Y values based on

map properties (e.g. Long/Lat or XY feet)


Export as shapefile XY events should be exported as

permanent shapefile or feature class


ARCCATALOG FUNCTIONSLecture 4


Basic functions

Copy, paste, rename, etc.


View and edit properties

Projections, fields, etc.


View metadata


Edit metadata


Create new files

Geodatabases, tables, features,

etc.


Summary Data types Geodatabases Data table joins Spatial joins Field calculator Calculate geometry ArcCatalog functions


Documents

Lecture 4 Geodatabases. Geodatabases Outline Data types Geodatabases Data table joins Spatial joins Field calculator Calculate geometry