Raster datasets and raster catalogs in a geodatabase in SQL Server

Raster datasets and raster catalogs in a geodatabase in SQL Server
Release 9.3

Rasters in ArcCatalog

Raster tables in a SQL Server DBMS

• The business table
The business table is a DBMS table that stores attributes and is spatially enabled by adding a raster column. It stores the footprint (delineates the area) of the raster. In the example above, the business table is the world_tif table.
A business table with a raster column is a raster dataset or a raster catalog. A raster dataset can have only one business table row, while a raster catalog can have more than one. Information about the raster column is maintained in the SDE_raster_columns system table.
Information about all business tables, regardless of whether or not they have a spatial column or raster column, is maintained in the SDE_table_registry system table.
• The feature table (f<layer_id>)
The feature table stores the geometry of the raster dataset. This table is identified by the number from the layer_id column of the SDE_layers table. The relationship between the business table and the feature table is managed through the Feature ID, or FID. This key, which is maintained by ArcSDE, is unique for the spatial column. In the example above, the feature table is f117.
• The spatial index table (s<layer_id>)
The spatial index table stores references to shapes based on a simple, regular grid. This table is identified by the number in the layer_id column in the SDE_layers table. In the World raster dataset example, the spatial index table is s117.
The spatial index contains an entry for each shape and grid cell combination to support spatial queries. When a spatial query is performed, the grid cells within the search area are identified and used to return a list of candidate pixels.
• Raster image tables
The actual raster images are stored in the following tables:
• SDE_AUX_<raster_column_ID>—The raster auxiliary table; stores the color map, statistics, and bit mask of the image
• SDE_BLK_<raster_column_ID>—The raster blocks table; stores the actual image data for each band of the image
• SDE_ BND_<raster_column_ID>—The raster band table; stores metadata about the bands of the image
• SDE_RAS_<raster_column_ID>—The raster description table; stores the description of the images within a raster column
ArcSDE geodatabases store raster bands in the raster band's table. ArcSDE joins the raster band's table to the raster table on the raster_id column. The raster band table's raster_id column is a foreign key reference to the raster table's raster_id primary key.
ArcSDE automatically stores any existing image metadata such as image statistics, color maps, or bit masks in the raster auxiliary table. The rasterband_id column of the raster auxiliary table is a foreign key reference to the primary key of the raster band table. ArcSDE joins the two tables on this primary/foreign key reference when accessing a raster band's metadata.
The raster blocks table stores the pixels of each raster band. ArcSDE tiles the pixels into blocks according to a user-defined dimension. ArcSDE does not have a default dimension; however, applications that store raster data in ArcSDE geodatabases do. ArcToolbox and ArcCatalog, for example, use default raster block dimensions of 128 by 128 pixels per block. The dimensions of the raster block, along with the compression method if one is specified, determine the storage size of each raster block. You should select raster block dimensions that, combined with the compression method, allow each row of the raster block table to fit within SQL Server.
The raster blocks table contains the rasterband_id column, which is a foreign key reference to the raster band table's rasterband_id primary key. These tables are joined together on the primary/foreign key reference when accessing the blocks of the raster bands.
The raster blocks table is populated according to a declining resolution pyramid. The height of the pyramid is determined by the number of levels, specified by application. The application, such as ArcToolbox or ArcCatalog, may allow you to define the levels, may request that ArcSDE calculate them, or may offer both possible choices.
The pyramid begins at the base, or Level 0, which contains the original pixels of the image. The pyramid proceeds toward the apex by coalescing four pixels from the previous level into a single pixel at the current level. This process continues until ArcSDE reaches the apex, which may be automatically defined or user-defined.
The additional levels of the pyramid increase the number of raster blocks by as much as one-third. However, since you can specify the number of levels, the size of the pyramid can be less. The first level of the pyramid will be 25 percent of the base. It should also be noted that the first level of the pyramid can be skipped; a factor that can greatly reduce the size of the pyramid.

When you build a pyramid, more rasters are created by progressively downsampling the previous level by a factor of two until the apex. As the application zooms out and the raster cells grow smaller than the resolution threshold, ArcSDE selects a higher level of the pyramid. The purpose of the pyramid is to optimize display performance.
The following are the table definitions for the raster tables:

NOTE: You will only have the raster tables in your geodatabase if you have raster data in the geodatabase.

SDE_aux_<raster_column_ID>
The raster auxiliary table stores the image color map, image statistics, and the optional bit mask, which is used for image overlays and mosaicking.



Field name	Field type	Description
rasterband_id	int	A number that represents a raster band; for example, a raster dataset with two raster bands would have two different values in this field—1 and 2
type	int	Values include 2 = raster statistics 3 = color map 4 = coordinate transformation 5 = reserved for geodatabase 6 = miscellaneous
object	image	Contains the actual data, either a color map index, raster statistics, or coordinate transformation

SDE_blk_<raster_column_ID>
The raster blocks table stores the image tiles.



Field name	Field type	Description
rasterband_id	int	A number that represents a raster band; for example, a raster dataset with two raster bands would have two different values in this field—1 and 2
rrd_factor	int	Pyramid level; pyramid levels begin at 0 and can increase from there
row_nbr	int	Tile row number position
col_nbr	int	Column row number position
block_data	image	Pixel data stored in the tile

SDE_bnd_<raster_column_id>
The raster band table stores information about the bands of the images. There is one record for each raster band.



Field name	Field type	Description
rasterband_id	int	A number that represents a raster band; for example, a raster dataset with two raster bands would have two different values in this field—1 and 2
sequence_nbr	int	Sequence of the raster band within the raster dataset
raster_id	int	The unique identifier of the raster dataset; corresponds to the value in the raster column of the business table
name	varchar(65)	The optional raster band name Nulls allowed
band_flags	int	A bit mask containing properties about the band
band_width	int	The pixel width of the band
band_height	int	The pixel height of the band
band_types	int	A bit mask containing properties about the band
block_width	int	The pixel width of a block
block_height	int	The pixel height of a block
block_origin_x	float	The x-ordinate of the raster origin
block_origin_y	float	The y-ordinate of the raster origin
eminx	float	The minimum x-value of a raster band; with eminy, emaxx, and emaxy, defines the envelope of a raster band
eminy	float	The minimum y-value of a raster band; with eminx, emaxx, and emaxy, defines the envelope of a raster band
emaxx	float	The maximum x-value of a raster band; with eminx, eminy, and emaxy, defines the envelope of a raster band
emaxy	float	The maximum y-value in a raster band; with eminx, eminy, and emaxx, defines the envelope of a raster band
cdate	int	The creation date of the raster band
mdate	int	The last modification date of the raster band

SDE_ras_<raster_column_id>
The raster description table stores the description of the images stored in a raster column.



Field name	Field type	Description
raster_id	int	The unique identifier of the raster dataset; corresponds to the value in the raster column that of the business table
raster_flags	int	Reserved for future use Nulls allowed
description	nvarchar(65)	The description of the raster dataset Nulls allowed

Rasters in an XML document

<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>sde.DEFAULT</Version> 
   <Domains xsi:type="esri:ArrayOfDomain" /> 
   <DatasetDefinitions xsi:type="esri:ArrayOfDataElement">
     <DataElement xsi:type="esri:DERasterDataset">
       <CatalogPath>/V=sde.DEFAULT/RD=sde.RJP.world_TIF</CatalogPath> 
       <Name>sde.RJP.world_TIF</Name> 
       <Children xsi:type="esri:ArrayOfDataElement">
          <DataElement xsi:type="esri:DERasterBand">
            <CatalogPath>/V=sde.DEFAULT/RD=sde.RJP.world_TIF/RB=Band_1</CatalogPath> 
            <Name>Band_1</Name> 
            <DatasetType>esriDTRasterBand</DatasetType> 
            <DSID>-1</DSID> 
            <Versioned>false</Versioned> 
            <CanVersion>false</CanVersion> 
            <HasOID>true</HasOID> 
            <OIDFieldName>ObjectID</OIDFieldName> 
            <Fields xsi:type="esri:Fields">
              <FieldArray xsi:type="esri:ArrayOfField">
                <Field xsi:type="esri:Field">
                    <Name>ObjectID</Name> 
                    <Type>esriFieldTypeOID</Type> 
                    <IsNullable>false</IsNullable> 
                    <Length>4</Length> 
                    <Precision>0</Precision> 
                    <Scale>0</Scale> 
                    <Required>true</Required> 
                    <Editable>false</Editable> 
                </Field>
                <Field xsi:type="esri:Field">
                    <Name>Value</Name> 
                    <Type>esriFieldTypeInteger</Type> 
                    <IsNullable>true</IsNullable> 
                    <Length>0</Length> 
                    <Precision>0</Precision> 
                    <Scale>0</Scale> 
               </Field>
               <Field xsi:type="esri:Field">
                    <Name>Count</Name> 
                    <Type>esriFieldTypeInteger</Type> 
                    <IsNullable>true</IsNullable> 
                    <Length>0</Length> 
                    <Precision>0</Precision> 
                    <Scale>0</Scale> 
               </Field>
             </FieldArray>
         </Fields>
         <Indexes xsi:type="esri:Indexes">
           <IndexArray xsi:type="esri:ArrayOfIndex" /> 
         </Indexes>
         <IsInteger>true</IsInteger> 
         <MeanCellHeight>0.175996089009095</MeanCellHeight> 
         <MeanCellWidth>0.176000337991447</MeanCellWidth> 
         <Height>1024</Height> 
         <Width>2048</Width> 
         <PixelType>U8</PixelType> 
         <PrimaryField>1</PrimaryField> 
         <TableType>esriRasterTableValue</TableType> 
         <Extent xsi:type="esri:EnvelopeN">
            <XMin>-179.906382261841</XMin> 
            <YMin>-90.1303147686327</YMin> 
            <XMax>180.542309944643</XMax> 
            <YMax>90.089680376681</YMax> 
            <SpatialReference xsi:type="esri:GeographicCoordinateSystem">
   <WKT>GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]]</WKT> 
          <XOrigin>-400</XOrigin> 
          <YOrigin>-400</YOrigin> 
          <XYScale>11258999068426.2</XYScale> 
          <ZOrigin>0</ZOrigin> 
          <ZScale>1</ZScale> 
          <MOrigin>0</MOrigin> 
          <MScale>1</MScale> 
          <XYTolerance>8.98315284119521E-09</XYTolerance> 
          <ZTolerance>2</ZTolerance> 
          <MTolerance>2</MTolerance> 
          <HighPrecision>true</HighPrecision> 
          <LeftLongitude>-180</LeftLongitude> 
         </SpatialReference>
        </Extent>
      </Data>
    </DatasetData>
   </WorkspaceData>
</esri:Workspace>