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Introduction to Geodatabases
ArcGIS 101 In this presentation we give an introduction to geodatabases.
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Objectives Give general background for those who are not familiar with geodatabases Introduce geodatabase terminology (feature classes, feature dataset, domain, raster catalog, etc.) You will not be a geodatabase expert… Outline the objectives of this presentation.. You will not be an expert in geodatabases as this is a complex subject. We just try to make you familiar with the data types and terminology we use in the class.
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Spatial data formats ArcGIS can work with spatial data in multiple formats Coverage Geodatabase Shapefile Internet Map Service CAD Spatial data formats Currently, there is not a standard format for GIS data. Various GIS software manufacturers and other organizations, such as government agencies, have continually searched for more efficient and versatile digital formats to store geographic information. ArcGIS has the advantage of seamlessly supporting all of the ESRI formats: shapefiles, coverages, GRIDs, the geodatabase, and data served over the Internet by ArcIMS and ArcGIS Server. ArcGIS also supports the three most common CAD file formats (DXF, DWG, and DGN), as well as a variety of common image formats. Having the ability to work with so many different formats without needing to convert them is a tremendous advantage. More information describing all of the data types supported by ArcGIS can be found in the ArcGIS Desktop Help files by entering the keywords ‘data types’ under the Index tab. Raster Tables ArcGIS Arc Hydro
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Defining the geodatabase
Collection of geographic datasets: Feature classes Raster data Attribute tables Models Native data structure for ArcGIS Provides the ability to: Leverage data relationships Enforce data integrity Create intelligent features Dimensions Cadastral Networks Surveys Addresses Annotation Vectors 3D Objects Topology CAD Images Terrain Attribute Cartography The geodatabase can store a wide array of data types. Big advantage as you can store all your datasets for a project in a central location with all of the capabilities of a RDBMS system (versioning, multiuser editing, put on a server, backups, etc.). It is now the standard data structure for storing ArcGIS data. Any ArcGIS application can read data from a geodatabase. Once data are loaded to the geodatabase there are also technical advantages: data relationships, enforcing data integrity in edit sessions, creating “intelligent features” – feature s that have some sort of behavior either in relation to other features, topology, networks, etc. Tools / Models Geodatabase Arc Hydro
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Geodatabase Personal and file GDBs Multiuser Functionality
Types of geodatabases: On the left you have the personal geodatabases (file and personal). Personal is based on an Access database, and file GDB is a file based system. In a file browser personal gdb will be an .mdb file, and file geodatabase will be a folder with a .gdb in the name. Multiuser GDB – includes different types of platforms: DB2, Informix, Oracle, PostgreSQL, SQL Server, For the Desktop and Workgroup levels - SQL Server Express. Functionality of standard RDBMS systems – Versioning, Replication, Archiving.
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Geodatabase elements Geodatabase Tables Feature dataset
Raster datasets Spatial reference Raster catalogs Feature classes Behavior Polygon Line Point Annotation Route Dimension Connectivity rules Relationship rules Topology rules Attribute defaults Attribute domains Relationship classes Toolboxes Go through the some of the important types of datasets we use in AHGW (we will expand on the important ones later in the presentation): Feature dataset – a collection (sort of a folder inside the geodatabase) for storing feature classes and relationships. Feature class – similar to a shapefile stored inside the geodatabase. Represents vector data (point, line, polygon). Special types of classes such as routes, dimensions, and annotations. Relationship classes – associate features and tables (the same as relationships in any RDBMS). Tables- store tabular data. Raster dataset and Raster Catalog – for storing images/grids. Many additional geodatabase data types (survey, terrain, topology, networks, CAD, etc.) You can also store tools and workflows in your geodatabase. Toolboxes store tools, models, and scripts So you can deliver the data + tools/models that support a certain workflow all in one geodatabase. Tool Model Script Geometric networks Additional geodatabase elements Survey datasets Terrain datasets Schematics Network datasets Topology Network datasets Arc Hydro
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Advantages of geodatabase
Central location for features and attributes Ability to create behavior Grouping features into subtypes Creating spatial and attribute validation rules Persistent relationships between records Referential integrity Stored connectivity between lines and points Many users editing database at one time File geodatabase and enterprise geodatabase Scalable Advantages: All your data in one location with the capabilities of regular RDBMS systems. Behavior – group features by subtypes, coded value domains for attributes, validation rules (spatial topology rules, range domains and coded values for attributes in feature classes/tables). Relationships between records – referential integrity – for example a house cannot be built where there is no lot – so if there is a relationship between the house and lot tables we can define that when the lot is deleted so are all the houses related to it. Connectivity between lines and points - build networks – utility, roads, railroads, river networks. Multi-editing – Scalable – all the advantages of standard database sytems (expand on servers, multi-users, backups, etc.). Arc Hydro
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Using geodatabases ArcCatalog - Schema editor ArcMap - Object editor
Create Geodatabase Define Feature Classes, Feature Datasets also: rename, copy, move, delete Set validation rules, subtypes, relationships, . ArcMap - Object editor Add, update and delete features, other objects ArcToolbox - Data loader and processor Shapefiles, coverages and tables to / from Geodatabase Geoprocessing tools We define the geodatabase - data elements, names, attributes, rules in ArcCatalog. If we use ArcMap to update features, edit, digitize, etc – this is how we “create the data” in an interactive way. We use ArcToolbox to load/export/convert datasets. We also use the toolbox to create data by “batch process data” example – calculate field, buffer, intersect, etc.
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Geodatabase tables Collections of rows and columns
Non-spatial element Stores attribute data, addresses, x/y locations, etc. May participate in relationships Talk about tables. Examples would be non-spatial data such as time series Arc Hydro
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Features Features are geographic objects
Object with a geometry attribute Vector model for geographic entities Features (rows) belong to Feature Classes (tables) Feature location is defined in the Shape field and has a geometry type: Point, Multipoint, Polyline, Polygon, and Multipatch Talk about features. Keep it general there will be more details in the next slides. Well Feature Class (table) . . . OID Shape Type Feature (row) . . . 524 X,Y,Z,M, ... Domestic
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Feature classes Table that stores geographic features and attributes
One type of geometry (point, line, polygon, annotation) Allows for XY coordinates and Z and M measures Has associated spatial reference Geographic coordinate system (GCS), projected coordinate system (PCS), and spatial extents Each record represents a feature Same behavior X and Y coordinates are mandatory. M and Z coordinates are optional. (M = measure along a line, Z = vertical coordinate) Each record = row in the table is a feature (point, line, polygon) All rows ( of a certain subtype) have the same behavior (attributes, relationships, domains, topology). Arc Hydro
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Feature datasets Element for storing spatially-related feature classes
Share same spatial reference Feature classes projected when loaded Tables cannot be stored in feature dataset Required for additional behavior Geodatabase topology Geometric network Network datasets Stand-alone feature classes Feature classes in feature dataset You can think of a feature dataset as a folder within the geodatabase used to group features. When you load feature classes into the feature dataset they are projected on the fly. Good to create a feature dataset at the beginning of your project – then you can just load data into it and all your data will be correctly projected. Can group different project data from different locations into a single geodtabaase – each project can get its own feature dataset. You must have a feature dataset defined to create topologies, geometric networks, and network datasets. Arc Hydro
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Relationships Must be in same geodatabase
Many possibilities for connecting tables Feature class to feature class or feature class to table Table to table or table to feature class Need common fields and logical connection ParcelToPermit Parcel (origin) Permit (destination) Datasets must be in the same geodatabase (can be in different feature datasets, or at the geodatabase level). Naming convention – Origin and Destination table. “Origin primary key” and “Destination foreign key”. In this example we see permits related with parcels – each permit must be related to a parcel (one or more) - you can make a rule that when a parcel is deleted all the permits are deleted as well. Parcel_ID Zone Block 123 • • • 456 789 Origin primary key FileDate • • • Parcel_ID Permit 456 1 789 2 123 4 3 Destination foreign key Arc Hydro
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Cardinality How many owners does each parcel have?
Composite relationships Always one-to-one or one-to-many cardinality One parcel has one owner One parcel has many owners Many parcels have one owner Many parcels have many owners Cardinality is defined when you construct the relationship. Determines how many features can participate in the relationship from each feature class. M-N relationship is a bit more complex as you need to add an intermediate table. Composite relationships are ones where the lifetime of one object controls the lifetime of its related objects. (e.g., deleting one feature deletes the related features in the related table). In AHGW we use 1-1 and 1-M relationships. You can add M-N relationships if necessary. or 1 - 1 1 - M 1 - M M - N Arc Hydro
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Geodatabase topology Defines valid spatial relationships for features
A specification of relative location In one feature class or between two feature classes Provides tools to maintain spatial integrity Created from feature classes in same feature dataset Edit using special tools in ArcMap Topology defines how features can spatially relate to each other – overlap or not, be contained, adjacent, etc. There are ~25 different topology rules. Can specify topology within a single feature classes – e.g. parcel must be adjacent Or between feature classes – house must be with a lot, or country must be within the coastline, or bus route must overlap the roads. Must be in the same feature dataset. Special tools in ArcMap for editing topology, visualizing errors, etc. Parcels Soil types Adjacency Coastline Country Roads Bus route Coincidence Arc Hydro
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Rasters in the geodatabase
Images and grids in ArcGIS Image formats (IMG, TIFF, BMP, many others supported) GRIDS (ArcInfo native raster format) Storage options: Raster dataset Single raster (aerial photo, satellite image) Raster catalogs Collections of raster datasets stored in a table Internal or referenced to file-based data Raster attribute You can attribute rasters in a catalog like any feature (index by type, time, etc). You can store many types of images within a raster dataset. Raster catalog – use to store a collection of rasters in a single table – advantage: can attribute and index. Two types of raster catalog: internal – rasters stored within the geodatabase file based – raster stored on disk and referenced by the catalog. Arc Hydro
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Create real-world feature behavior in geodatabase
Geodatabase behavior Specific to geodatabase Subtypes Categorize features into groups Domains Attribute validation on a field Topology rules Spatial validation rules Relationship class rules Determine proper associations between records Connectivity rules Determine proper connections between network features Create real-world feature behavior in geodatabase Two of the greatest concerns to most organizations are data integrity and efficiency during management, display, and editing operations. The behavior/validation rules support better data management: Subtypes – can categorize features into groups - e.g. Shoreline and Flow line – both are lines but totally different behavior. So they will have different rules associated with them even though they are in the same feature class. Domains – validation on a field – range, a list of predefined values. Topology – spatial rules. Relationships – how features are linked with other features. Connectivity – connections in a network. Arc Hydro
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Geoprocessing Geodatabase can store:
Toolboxes: Containers for tools and toolsets Toolsets: Logical containers of tools Tools: Single geoprocessing operations Models and script tools Toolbox Toolset System tool Script Model Student notes Arc Hydro
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ArcGIS Data Models Templates for Many Fields
Address Agricultural Atmospheric Base Map Biodiversity Building Interior Spaces Census-Admin Boundaries Defense-Intel Energy Utilities Environmental Fire Service Forestry Geology GIS For The Nation Groundwater Health Historic Preservation & Archaeology Homeland Security Hydro IHO - Navigation Land Parcels Local Government Marine National Cadastre Petroleum Pipeline Telecommunications Transportation Water Utilities Help Users Get Started Support Standards Website:
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Terms you should be familiar with
Geodatabase Feature class Feature dataset Relationship Coded Value Domain Raster Raster Catalog Projection Geodatabase Schema Topology At this point ask the class to view these terms and see if they are all familiar with the terms. Take questions if they are not familiar with any of the terms.
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Resources ESRI Website:
data/geodatabases/what-is-a-geodatabase.htm ArcGIS Desktop Web Help: - Go to “Professional Library | Data Management |Managing Geodatabase” section. Online classes - Search for “Geodatabase”
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