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28 Cards in this Set
- Front
- Back
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Text files (.txt, .csv)
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-Simplest way to store data
-Best way to store attribute data -Highly portable Not good way to store complex gedata |
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Shape files (.shp)
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-Best way to store geodata if you want to send one/few files
-Useable by anyone w/ArcGIS, ArcExplorer, etc. Not good for large amounts of data |
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Keyhole Markup Language files (.KML)
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-Google Earth Format
-Good way for public dissemination Limited in what you can express, i.e. no network analysis |
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Layer files (.lyr)
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-Good for distributing shapefiles that must be viewed with symbology
Only viewable in ArcGIS |
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ArcMap files (.mxd)
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-Useful for organizing layers
-Stores symbology along w/map design Not easy to dsitribute .mxd without including all associated layers (better to distribute as PDF) |
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Coverage files
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-Enforces topology
-Represent middle point between transition from shapefiles to geodatabases OBSOLETE; DO NOT USE |
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Geodatabase (.gdb, .mdb)
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-Best way to store geodata
-Compliant with latest standards of storage -Can enforce topology -Can create joins and queries |
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Geographic database/Geodatabase
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Database contains geographic data of a set of objects for particular area
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Database
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Organized and integrated set of data on particular subject
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Advantages of geodatabases
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-More accurately represent shape of features
-Many users can edit geographic data simulatenously -ESRI's preferred format -Efficient storage: all layers in one database -Ensures various geodata are compatible -Validates topology, easier to spot/correct errors |
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Geodatabase structure
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-Feature class: collection of features sharing same geometry type
-Feature dataset: collection of feature classes (all must have same spatial reference) -Nonspatial table: contains attribute data assoc. w/feature classes |
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Relational databases
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Data represented and stored as set of tables
-Objects in table have same set of attributes |
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Attribute of object: Data types
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String
Number Date Geometry, etc. |
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Primary Key
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One/several columns (attributes) selected that can distinguish one object from others
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Primary key has 2 properties
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1. Each value in attribute column is unique
2. No null values |
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Candidate keys
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Alternatives to primary keys
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Directly loadable data types
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.dbf
.csv .xls .mdb |
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Types of geodatabases:
Enterprise geodatabase |
-Multiple users
-Requires host database system (DBMS) |
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Types of geodatabases:
Personal geodatabase |
-Single user
-Appears as .mdb |
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Types of geodatabases:
File geodatabase |
Newer format by ESRI
-Preferred, much larger file sizes -Better performance -More efficient storage USE .GDB WHENEVER POSSIBLE |
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DBMS
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Database Management System
-Organizes/manipulates data -Stores properties of geographic objects and relationships -Acts as gatekeeper |
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Benefits of DBMS
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-Data independence
-Multiple user views (simultaneous viewing) -Centralized control/maintenance of important data |
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Most common spatial databases?
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Relational and object-relational
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Data table joins
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Putting 2 tables together to make 1 table
-Must have same values and data types |
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Problems with joins
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-Data in fields not exactly same
-Different data field types |
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Spatial join
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Merges rows based on objects' spatial relationships (each row represents a geographic object)
-Based on "shape" not attribute field (overlap/within/contains, etc) |
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SQL
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Structured Query Language
-International standard language for manipulating relational databases |
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Relational operators (8)
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1. Restrict: reduce rows
2. Project: reduce columns 3. Product: produces all possible combinations 4. Divide: only cells meeting all critera 5. Union: merges rows together 6. Intersect: returns matching rows in both tables 7. Difference: returns rows that do not appear in 2nd table 8. Join: combines rows of two tables based on matching primary keys |
