GeoDatabaseExtensions

The GeodatabaseExtensions library contains objects that aid in the creation, management, and use of terrain datasets and cadastral fabrics.

Note: At the 9.2 release, the cadastral fabrics related objects are not yet fully implemented, and developers should not utilize them until the Cadastral Analyst extension is released.

The creation, management, and use of terrain datasets are achieved primarily through four classes: Terrain , TerrainPyramidLevel, TerrainDataSource , and DynamicSurface.

Terrain

A terrain is a multi-resolution, triangulated irregular network (TIN)-based surface comprised of measurements stored in feature classes inside a geodatabase. The Terrain component resides in a feature dataset next to the feature classes that participate in the terrain. While terrains are TIN based, the triangle-based structure is not actually persisted. Rather, just the measurements are stored along with rules that control how the measurements are used. TIN surfaces are made on the fly based on terrain queries that extract measurements on demand.

TerrainPyramidLevel

A terrain pyramid is a vector-based structure used to optimize surface-based queries on original source measurement data. Just the measurements that are required for a given area of interest (AOI) and level of detail (LOD) are pulled from the geodatabase and triangulated into a memory-based TIN. The surface is dynamic, changing based on AOI and LOD queries. A terrain pyramid arranges the measurements into levels that are used for scale dependent generalization. Relatively few measurements are in the coarsest level for small scale applications that require less accuracy. Additional measurements are included for higher detail levels until the full resolution level is reached where all measurements get used.

TerrainPyramidLevel is an abstract class. TerrainPyramidLevelZTolerance is available for defining pyramid levels based on vertical tolerance.

TerrainDataSource

Each feature class that participates in a terrain has a set of properties that indicate how it contributes to the terrain surface. The feature class and its corresponding properties are encapsulated into an object called TerrainDataSource.

DynamicSurface

DynamicSurface is instantiated by Terrain and is used to extract TINs, rasters, and measurements based on area of interest and level of detail queries.

TerrainDataImporter

TerrainDataImporter is an abstract class. Two types of importers are TerrainAsciiDataImporter and TerrainLasDataImporter. These are used to import three-dimensional (3D) measurement data suitable for use in a terrain. The ASCII data importer reads points in XYZ and 3D GENERATE text file formats. The LAS importer is for LIDAR data stored in the LAS binary format.