RDMS, geodatabases, ARCSDE

Spatial Index Factors

• Try to have as large a grid size as possible (to reduce # of cells) • Have the fewest number of features per grid • Ideally with most features referenced by a single tile • Also want the grids per feature ratio < 2 • Can have up to 3 grids. This can help with data sets with many VERY large features with large envelopes

ArcSDE Feature classes

•Each feature class is stored as one or more tables •Each feature is a ROW •A "spatial column" (e.g., shape) stores the geometry

What is ArcSDE

- it allows us to store and manage our spatial data within tables in a database (vector and raster -"spatially enables" a RDBMS -provides communicating between a GIS client and the database -ArcSDE is available for Oracle, SQL Server, DB2 Informix, and PostGres

personal geodatabase

-All datasets are stored within a Microsoft Access data file. -2GB (Access) -Only vector feature classes are actually stored inside the Access database -4 users but only one editor -Does not support versioning

geodatabase storage

-Feature Class (Point/Lines/Polygons) -Table -Raster Dataset

spatial grid sizes

-Spatial Grid 1 is the first, or lowest, grid level and has the smallest cell size. -Spatial Grid 2 should be at least three times as large as Spatial Grid 1 -Spatial Grid 3 at least three times as large as Spatial Grid 2

file geodatabase

-Stored as folders in a file system. -Each dataset is held as a file that can scale up to 1 TB in size. -Multi-user (max = 10) -1 Editor (no versioning

Enterprise geodatabase (based on ArcSDE)

-Stored in a relational database using Oracle, Microsoft SQL Server, IBM DB2, IBM Informix, or PostgreSQL. -These multiuser geodatabases require the use of ArcSDE and can be unlimited in size and numbers of users. -Supports versioning

How ArcSDE uses the Spatial Index

Goal is to analyze the geometry of the FEWEST number of features possible (most computationally efficient) •ArcSDE determines the features meeting the query based on a series of filters that start with the Spatial index -Continually refines the "candidates"

spatial Index

Index is based on a grid superimposed over feature class • Stored as a separate table for each feature class • Contains a row for each grid/feature combination

Geodatabase

a "container" used to hold a collection of datasets/layers. There are three types: -personal geodatabase -file geodatabase - enterprise geodatabase

Relational Database Management System( RDMS)

a database that has a collection of tables of data items, which are all formally described and organized according to a relational model

why SDE continued

•Allows large, seamless layers •Centralized access •"Intelligent" server (only sends features that are needed) •Long transactions, true multi-user editing (e.g., versioning) •Data security (RDBMS) •Leverage Advanced RDBMS func. (e.g., Replication)

Why SDE

•Better model for integrating spatial and non-spatial data (all in RDBMS, easier joins, etc.) •FAST retrieval of small # of features from LARGE tables •Provides TCP/IP access (navigating firewalls) •High performance data serving to many users (instead of file based), takes advantage of RDBMS strengths

Statistics (Analyze)

•DBMS' arrive at an execution plan for each query •Execution plans are based on table statistics •We want to avoid full table scans •Should create statistics for a FC at creation and after major edits •Can be done in ArcCatalog (on indiv. FC), or in batch in DBMS

ArcSDE Feature class organization

•Each feature class has an "owner". This is the user ( group not individual) that loads the feature class. •The full name of a feature class is owner.fc (e.g., syra.parcels) •We "organize" our feature classes within a geodatabase using owner names (as prefixes). -Ball.parcels vs clif.parcels

benefits of enterprise GIS

•Increased access to data, tools and information •Enables better and more expedient decision making •Integrates the entire organization regardless of Dept or geographic location (e.g., regional offices) •Fully leverages the geographic value of data in the org. •Eliminates data redundancy •increases efficiency •Standardizes business processes and output products •Allows the effective utilization of outside data & information •Promotes sharing of data with others •Centralizes and simplifies system administration

granting privileges

•Owner will have full access (Select, Update, Insert and Delete) •Others need to be granted privileges