Managing data

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This section describes how to work with feature classes, tables and the datasets that manage them; that is, relationship classes, topologies, and geometric networks. This includes how to create them, modify their schema, and query them. It also includes topics involving geodatabase management, such as how to create or open a geodatabase, how to work with versioned data, how to use replication, and how to import and export data to and from a geodatabase. For more information on specific topics, see Working with feature data.

Developers using this content should have some familiarity with geodatabases, the types of datasets in a geodatabase, and any workflow-specific concepts that they require. For example, the versioning topics in this section only discuss how to programmatically execute versioning workflows, not the requirements of versioning or how the technology works.

Developers working with non-geodatabase vector data, such as shapefiles and computer-aided design (CAD) datasets, will also find the topics in this section useful. Many of the application programming interfaces (APIs) for working with datasets stored in geodatabases are also used to work with datasets from these data sources. Additionally, the "Other data sources" section describes specific differences.

A notable related topic not included in this section is editing data. For more information about editing, see ArcGIS Desktop editing for developers (for ArcGIS Desktop developers) or ArcGIS Engine editing (for ArcGIS Engine developers).

In ArcGIS, image and raster data are managed as raster datasets, raster catalogs, and mosaic datasets. This section describes how to create and load raster data to each of these data types, how to work with the properties of raster datasets, such as color map, and how to display these data types in ArcMap. It also includes topics on how to serve raster data through ArcGIS Server. For more information on specific topics, see Working with image and raster data.

Image geometric and radiometric transformations are fundamental image processing techniques. ArcGIS supports common geometric transforms, such as polynomial or adjust (rubbersheeting) transform, as well as sensor models, such as rational polynomial coefficient (RPC) or frame camera, which enable the capabilities of reading image data from multiple sensor platforms. This section includes samples on how to work with these transforms for geometric transformation, raster functions for radiometric (pixel) transformation, and raster types for working with data from various sensor platforms. This section also includes topics on how to add custom transforms, raster functions, and raster types to ArcGIS. For more information, see Processing raster data.

The main purpose of this section is to introduce developers to the classes and interfaces of the Geometry library. Top-level geometries, such as points, multipoints, polylines, polygons, and multipatches are introduced in a series of topics. This includes how to create and modify geometry features using different building blocks (paths, rings, segments, triangle strips, triangle fans, and triangles). Some geometry operations—such as, simplify and union—that can be applied to top-level geometries are also discussed along with the relevant interfaces. Other important interfaces that are covered include IGeometryBridge, IGeometryBag, and IGeometryCollection. For more information, see Working with geometry.

All vector data is georeferenced to the real world through a spatial reference. A spatial reference includes the coordinate system and several coordinate grids. A coordinate system includes information, such as the unit of measure, the earth model used, and sometimes, how the data was projected. The coordinate grids are mathematical functions that define the x-,y-,z-, and m-resolution values and the corresponding domain extents for the coordinate grids. The resolution values are similar to the cell size of a raster. Each spatial reference also has a set of tolerance values. A geometry’s coordinates (or vertex attributes) must fall within the domain extent and are rounded to the nearest intersection of the coordinate grid as defined by the resolution. The tolerance values are used by geometric operations that relate coordinates or compute new ones. A raster's spatial reference contains the coordinate system only. Its grid extents and cell size correspond to the coordinate grid and resolution.
 
X,y values can be georeferenced with a geographic or projected coordinate system. A geographic coordinate system (GCS) is defined by a datum, an angular unit of measure, usually either degrees or grads, and a prime meridian. A projected coordinate system (PCS) consists of a linear unit of measure, usually meters or feet, a map projection, the specific parameters used by the map projection, and a GCS. A PCS or GCS can have a vertical coordinate system (VCS) as an optional property. A VCS georeferences z-values. A VCS includes either a geodetic or vertical datum, a linear unit of measure, an axis direction, and a vertical shift. M-values (measure values) do not have a coordinate system.
 
A spatial reference that includes an unknown coordinate system (UCS) includes a grid (domain extent) and a tolerance only. It is not possible to georeference a geometry associated with a UCS. If at all possible, you should not use a UCS. When a GCS or PCS is used, appropriate default x,y domain extent, resolution, and tolerance values can be calculated. All grid and tolerance information for coordinates and attributes are associated with the PCS, GCS, or UCS. A VCS georeferences z-coordinates but does not have a well-defined default grid.

Spatial reference information is very important. Without it, the software cannot combine two datasets together and get meaningful results. For more information, see Working with spatial references and Understanding coordinate management in ArcGIS.

Time can be expressed in various ways and in various formats. This section describes the different formats of time data that can be used by ArcGIS to work display time-related information in a meaningful way. Many of the layers in ArcGIS are able to display time data by identifying which attributes of a feature class contain the time data. Several ArcObjects are also available to help calculate time values and deal with time zone issues. For more information, see Working with time data.

NetCDF (network Common Data Form) is a file format for storing multidimensional scientific data, such as temperature, humidity, pressure, wind speed, and direction. The data in a netCDF file is stored in the form of arrays. Each of these variables can be used in ArcGIS by making a layer or table view from the netCDF file. Several ArcObjects are available in the DataSourcesNetCDF library to work with a netCDF file. However, since all the functionalities are available through geoprocessing tools, it is not necessary to use these objects. For more information, see Working with netCDF data.