Terrain datasets in a geodatabase in SQL Server

Terrain datasets in a geodatabase in SQL Server
Release 9.3

NOTE: Requires 3D Analyst extension

Terrain datasets are surfaces that represent three-dimensional space. They use measurements (stored as feature classes) and rules to generate TIN pyramids to represent elevation.

The source feature classes either can be referenced by the terrain dataset or be embedded in the terrain dataset.

For an explanation of terrain datasets, read the topics in the book Understanding terrain datasets. You can begin with the topic What is a terrain dataset?

Terrains in ArcCatalog

In the Catalog tree, terrain datasets in a SQL Server database management system (DBMS) look like any other feature dataset. The difference is terrain datasets contain a terrain. In the example below, the napa_sub terrain dataset contains the terrain napa_sub_terrain1.

Terrain dataset in ArcCatalog (SQL Server)

You can see two of the feature classes that participate in the terrain—napa_sub_breaks and napa_sub_clip. To find out if there are any embedded feature classes in the terrain dataset, check the terrain properties. Right-click the terrain, and click the Data Sources tab. This will list all feature classes used to create the terrain. In this example a third, embedded feature class—napasub_embedded—was used to create this terrain.

Feature classes used as the data source for a terrain

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Terrains in a SQL Server DBMS

Being datasets, terrain datasets are managed in the geodatabase in the same tables as feature datasets, plus there are terrain-specific tables created in the schema of the user who created the terrain dataset. These tables are as follows:

DTM_<ID>_COMPOSITETILES

Composite tiles are incomplete, in terms of data coverage, around their perimeter. They could be void of measurements entirely or within the proximity of one or more corners. To define a surface that covers the extent of these tiles data is used from surrounding tiles. This table is used to identify which tiles are composite tiles and what neighboring tiles provide data to complete them. One record is used per composite tile.

Field name	Field type	Description
ID	ObjectID	The unique identifier of the shape pointing to neighbor tiles.
TileNr	Long	The composite tile number. This is defined by the terrain's tile system. A value of -1 is reserved for one record containing the centroids of the terrain's perimeter tiles.
EmptyTile	Short	A value of -1 indicates the tile is void of any measurements. A value of 0 indicates the tile has some data but is incomplete.
OtherTiles	BLOB	Multipoint shape storing the tile centroid of each surrouding tile that provides measurements to complete the composite tile.

DTM_<ID>_DIRTYAREA

Dirty areas are tiles that have been invalidated as a result of edits to features in one or more participating feature classes. This table is used to keep track of these invalidated tiles and to record in which feature classes the edits have taken place. One record is used per feature class. The table will be empty if no edits have been made.

Field name	Field type	Description
ID	ObjectID	The unique identifier for the shape.
ClassID	Long	The ID of the feature class that's been edited.
TileCount	Long	The number of dirty tiles resulting from edits to the feature class.
DirtyArea	BLOB	Multipoint shape containing the tile centroids invalided as a result of edits to the feature class.

DTM_<ID>_EMBED_#

Embed tables are used to store embedded multipoint feature classes. There may be 0..n embed tables. Their existance depend on whether the terrain has any embedded data. One table is used per embedded feature class. An embed table has the dual purpose of being part of the terrain's pyramid structure. The embedded data are grouped by tile and pyramid level.

Field name	Field type	Description
ID	ObjectID	The unique identifier for the shape
TileRow	Long	The row number of the terrain tile to which the embedded points belong
TileCol	Long	The column number of the terrain tile to which the embedded points belong
Resolution	numeric(38,8)	Indicates in which pyramid level(s) the points are used Since pyramid levels are cumulative, points participate in levels with resolutions equal to or greater than themselves A special case involves the terrain overview. The resolution of the overview level is indicated with a value of -1. Points assigned this value participate through the entire pyramid.
PointCount	Long	The number of points in the multipoint
NeighborData	smallint	Indicates whether points are inside the tile neatline boundary; Those outside are used to ensure complete coverage of the tile area. A value of 0 indicates the points are inside the tile. -1 indicates they are outside.
Shape	BLOB	Embedded multipoint geometry

DTM_<ID>_INSIDETILES

The InsideTiles table is used to record which terrain tiles are within the data area, or interpolation zone, of the terrain. This is recorded per pyramid level because it's possible for the extent to differ across levels (i.e. with the use of different clip polygon feature classes in different pyramid levels). One record is used per pyramid level. This includes both overview and full resolution levels.

Field name

Field type

Description

ObjectID

The unique identifier for the shape

ZTolerance

numeric(38,8)

The resolution of the pyramid level

A value of -1 indicates the overview level.

InsideTiles

BLOB

Multipoint geometry storing the data tile centroids

DTM_<ID>_MRFC

The MRFC is the pyramid structure for non-embedded feature classes. Mass points and breakline vertices for referenced feature classes are stored here under the pre-condition they participate in the full resolution pyramid level (they can also participate in other levels). Data are grouped by tile and pyramid level.

Field name	Field type	Description
ID	ObjectID	The unique identifier for the shape
TileRow	Long	The row number of the terrain tile to which the pyramid points/vertices belong
TileCol	Long	The column number of the terrain tile to which the pyramid points/vertices belong
Resolution	numeric(38,8)	Indicates in which pyramid level(s) the points are used Since pyramid levels are cumulative, points participate in levels with resolutions equal to or greater than themselves. A special case involves the terrain overview. The resolution of the overview level is indicated with a value of -1. Points assigned this value participate through the entire pyramid.
PointCount	Long	The number of points in the multipoint
NeighborData	smallint	Indicates whether points are inside the tile neatline boundary; those outside are used to ensure complete coverage of the tile area. A value of 0 indicates the points are inside the tile. -1 indicates they are outside.
Shape	BLOB	Multipoint geometry

DTM_<ID>_PROPS

The terrain props table is used to hold version specific properties for an individual terrain dataset. These include point count and extent. The information is stored in a BLOB and is not user accessible through the table. Instead, use terrain's ArcObjects API to access the information.

Field name	Field type	Description
ID	int	The ObjectID for the record
Properties	image	Stores the version specific dataset properties nulls allowed

Field name

Field type

Description

int

The ObjectID for the record

Properties

image

Stores the version specific dataset properties

nulls allowed

A record is also created in the GDB_EXENSTIONDATASETS table to track the terrain dataset. The ID in the names of the DTM tables come from the ID field of the GDB_EXTENSIONDATASETS table.

As mentioned, terrain datasets are tracked with the same system tables as feature datasets. The additional tables for a terrain dataset are shown below. The 2 in the example DTM_* table names relates these tables to the ID field in the GDB_EXTENSIONDATASETS table.

Terrain dataset system tables in SQL Server

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Terrains in an XML document

Terrain datasets are denoted in an XML document with the dataset type ersriDTTerrain.

<DatasetType>esriDTTerrain</DatasetType>

The following is a portion of the XML document for the napa_sub terrain dataset. The XML document excerpt below covers the definition of the dataset, including data sources, up to the point of describing the first feature class in the dataset.

 <esri:Workspace xmlns:esri="http://www.esri.com/schemas/ArcGIS/9.2" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <WorkspaceDefinition xsi:type="esri:WorkspaceDefinition">
  <WorkspaceType>esriRemoteDatabaseWorkspace</WorkspaceType> 
  <Version>RJP.WO2557</Version> 
  <Domains xsi:type="esri:ArrayOfDomain" /> 
  <DatasetDefinitions xsi:type="esri:ArrayOfDataElement">
    <DataElement xsi:type="esri:DEFeatureDataset">
      <CatalogPath>/V=RJP.WO2557/FD=sde.RJP.napa_sub</CatalogPath> 
      <Name>sde.RJP.napa_sub</Name> 
      <Children xsi:type="esri:ArrayOfDataElement">
        <DataElement xsi:type="esri:DETerrain">
          <Version>2</Version> 
              <CatalogPath>/V=RJP.WO2557/FD=sde.RJP.napa_sub/TERR=sde.RJP.napa_sub_terrain1</CatalogPath> 
          <Name>sde.RJP.napa_sub_terrain1</Name> 
          <DatasetType>esriDTTerrain</DatasetType> 
          <DSID>2</DSID> 
          <FeatureDatasetName>sde.RJP.napa_sub</FeatureDatasetName> 
          <Versioned>false</Versioned> 
          <CanVersion>false</CanVersion> 
          <ChildrenExpanded>true</ChildrenExpanded> 
          <MetadataRetrieved>false</MetadataRetrieved> 
          <FullPropsRetrieved>true</FullPropsRetrieved> 
          <PyramidType>0</PyramidType> 
          <TileSize>6000</TileSize> 
          <MaxShapeSize>5000</MaxShapeSize> 
          <MaxOverviewSize>50000</MaxOverviewSize> 
          <TerrainDataSources xsi:type="esri:ArrayOfTerrainDataSource">
            <TerrainDataSource xsi:type="esri:TerrainDataSource">
              <Version>1</Version> 
              <FeatureClassID>875</FeatureClassID> 
              <FeatureClassName>sde.RJP.DTM_2_DISCONNECT_3</FeatureClassName> 
              <GroupID>1</GroupID> 
              <SourceStatus>1</SourceStatus> 
              <SourceType>1</SourceType> 
              <SurfaceFeatureType>18</SurfaceFeatureType> 
              <IsBase>true</IsBase> 
              <ApplyToOverview>true</ApplyToOverview> 
              <AutoGeneralize>false</AutoGeneralize> 
              <ResolutionLowerBound>0</ResolutionLowerBound> 
              <ResolutionUpperBound>0</ResolutionUpperBound> 
              <SourceName>napasub_embedded</SourceName> 
              <HeightField>Shape</HeightField> 
              <TagValueField /> 
              <ReservedFields xsi:type="esri:ArrayOfString" /> 
           </TerrainDataSource>
           <TerrainDataSource xsi:type="esri:TerrainDataSource">
              <Version>1</Version> 
              <FeatureClassID>874</FeatureClassID> 
              <FeatureClassName>sde.RJP.napa_sub_breaks</FeatureClassName> 
              <GroupID>2</GroupID> 
              <SourceStatus>1</SourceStatus> 
              <SourceType>0</SourceType> 
              <SurfaceFeatureType>1</SurfaceFeatureType> 
              <IsBase>true</IsBase> 
              <ApplyToOverview>false</ApplyToOverview> 
              <AutoGeneralize>false</AutoGeneralize> 
              <ResolutionLowerBound>0</ResolutionLowerBound> 
              <ResolutionUpperBound>2.6</ResolutionUpperBound> 
              <SourceName /> 
              <HeightField>Shape</HeightField> 
              <TagValueField /> 
              <ReservedFields xsi:type="esri:ArrayOfString" /> 
           </TerrainDataSource>
           <TerrainDataSource xsi:type="esri:TerrainDataSource">
              <Version>1</Version> 
              <FeatureClassID>873</FeatureClassID> 
              <FeatureClassName>sde.RJP.napa_sub_clip</FeatureClassName> 
              <GroupID>3</GroupID> 
              <SourceStatus>1</SourceStatus> 
              <SourceType>0</SourceType> 
              <SurfaceFeatureType>10</SurfaceFeatureType> 
              <IsBase>false</IsBase> 
              <ApplyToOverview>true</ApplyToOverview> 
              <AutoGeneralize>false</AutoGeneralize> 
              <ResolutionLowerBound>0</ResolutionLowerBound> 
              <ResolutionUpperBound>31</ResolutionUpperBound> 
              <SourceName /> 
              <HeightField /> 
              <TagValueField /> 
              <ReservedFields xsi:type="esri:ArrayOfString" /> 
           </TerrainDataSource>
         </TerrainDataSources>
         <TerrainPyramidLevelZTols xsi:type="esri:ArrayOfTerrainPyramidLevelZTol">
           <TerrainPyramidLevelZTol xsi:type="esri:TerrainPyramidLevelZTol">
           <Version>1</Version> 
           <PyramidLevelStatus>1</PyramidLevelStatus> 
           <PointCount>-1</PointCount> 
           <MaxScale>10000</MaxScale> 
           <Resolution>5</Resolution> 
         </TerrainPyramidLevelZTol>
         <TerrainPyramidLevelZTol xsi:type="esri:TerrainPyramidLevelZTol">
           <Version>1</Version> 
           <PyramidLevelStatus>1</PyramidLevelStatus> 
           <PointCount>-1</PointCount> 
           <MaxScale>20000</MaxScale> 
           <Resolution>10</Resolution> 
         </TerrainPyramidLevelZTol>
       </TerrainPyramidLevelZTols>
      </DataElement>
      <DataElement xsi:type="esri:DEFeatureClass">

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Terrain datasets in a geodatabase in SQL Server

Terrain datasets in a geodatabase in SQL Server

Terrains in ArcCatalog

Terrains in a SQL Server DBMS

Terrains in an XML document

See Also