lecture 4 geodatabases

Lecture 4Geodatabases

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)


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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


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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


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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 usersINF385T(28437) – Spring 2013 – Lecture 4

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New file geodatabase

ArcCatalog


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Import into geodatabase


Shapefile features

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Import into geodatabase Tables


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Export from geodatabase


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View geodatabases Cannot identify names in Windows

Explorer Must use ArcCatalog


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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


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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


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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


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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.


FIPS01001010030100501007

GEO_ID21001100310051007

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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


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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)


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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


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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


lecture 4 geodatabases

Documents

users9inf385t28437 spring

data table joinsputting

xls 4inf385t28437 spring

toc 15inf385t28437 spring

format 16inf385t28437

data table formatsfirst

censusdata table

source table