Databases and GIS

1. Databases and GIS Benjamin Post Cole Kelleher

2. Availability • Data must maintain a specified level of availability to the users • Performance • Database requests must be executed within time thresholds • Isolation between users • Concurrency • Commits/Rollbacks • Data Independence • Reduces redundancy, storage requirements • Self-describing • Able to describe the stored data using schemas Database Characteristics

3. Comprised of relations between individual pieces of data Concepts: • Table • Also known as relation, contains attributes and tuples • Attributes • Columns, stores the individual pieces of data • Tuples • Rows, forms the relationship between the data in the columns. • MUST BE UNIQUE ENTRY Relational Databases

4. Diagrams Entities and their Attributes, and the Relationship between entities. Entity-Relationship Model Employee Office Branch 1 N Works at Name Start Date Salary Address Office Hours Office Phone

5. Comprised of objects stored in memory Concepts: • State • Defines information about the object, i.e. geographic location • Behaviors • Actions that the object can perform or actions which modify an object • Inheritance • Similar to Object-Oriented Programming, objectscan inherit state and behavior from other objects Object-Oriented Databases

6. Built on set theory and relational algebra • Data definition language • SQL can be used to define and create the database • Data manipulation language • INSERT • UPDATE • DELETE • Queries via SELECT Structured Query Language (SQL)

7. Geometries in Oracle Spatial are split into two data types: • SDO_GEOMETRY • Stores the geometry as is. • Requires a larger storage space due to redundancy. • Useful for queries that retrieve the entire geometry of a feature. • SDO_TOPO_GEOMETRY • Stores geometry using topological elements. • Allows for topology management over multiple features. • Decreased redundancy and thus decreased storage space. • Supports topological queries and processing Oracle Spatial is an open format and is compliant on a large number of platforms. Geometry data types are restricted to two dimensions. Oracle Spatial – Geometries and Rasters

8. GeoRaster in Oracle Spatial is used to handle raster data. • Uses its own “GeoRaster” data type to standardize the rasters stored in the database instead of storing the variety of raster file types that exist. • Employs the SDO_GEORASTER data type for the storage of the raster data. • Also uses the SDO_GEOMETRY data type to store the spatial extent of the raster data for ease of indexing. • This is a logically layered multidimensional data model that stores each raster band as a layer. • Further development needed in geoprocessing and modeling capabilities.

9. Post GIS is an extension of PostgreSQL for spatial databases. • Certified under the OGC as a “Simple Features for SQL” database. • Supports spatial joins in which two tables are joined on a spatial relationship. • OGC compliancy means it is applicable to a large quantity of open source software and some proprietary software. • Further development is needed for three dimensional modeling and raster integration. PostGIS

10. Geographic Resources Analysis Support Software (GRASS) GRASS is an open source GIS package that can conduct spatial analysis and modeling. • Supports both vector and raster data with three dimensional capabilities. • Is able to interact with a variety of useful software packages to aid statistical operations, spatial analysis and processing. • GRASS is OGC compliant which means its source code is available for the user to manipulate to fit his or her needs and contribute to the software itself. • High level interoperability means an increase in flexibility and performance. • GRASS is able to connect to a variety of RDBMS for ease of integration.