Raster Reprojection



Raster Manager supports on-the-fly reprojection of any geocoded and georeferenced image. 

Reprojection In Raster Manager Dialog

Raster Manager provides three columns of information which are related to raster reprojection.  They are: 

To display these columns, right-click the title of any column name and enable their display  in the resulting picklist.

Raster Manager - Reprojection Related Columns


Georeferencing is the operation of positioning a raster in the world by using the following six parameters :


Sister Files

A sister file is a text file stored in the same folder as the image it georeferences.  It has the same name as the image, but has a different extension. A sister file is usually used with raster file that doesn't support georeferencing.

Raster Manager supports the following sister files :


Setting The Georeference

Specifying the georeference can be done manually by using the basic transformation tool found in the Raster Manager.  For additional information, refer to:  Raster Manager - Basic Raster Editing.  This is not recommended  for precise georeferencing.

When the exact six transformation parameters are known, it's possible to create a sister file and manually write the transformation parameters to it.

A more precise approach is to register the raster with Bentley Descartes.  Please refer to Bentley Descartes - Raster Registration for more information.


Georeference Preferences

Found in the Raster Manager category of the Preferences dialog, georeference preferences can affect the final georeference attributed to a file.

Raster Manager - Georeference Preferences



Extra:  EPSG stands for European Petroleum Survey Group  which has defined numeric identifies for common projections and coordinate metadata.  These codes are industry standards and are used with MicroStation as well as other products.



Geocoding is information describing the coordinate system for which the georeference is applied. It's the geocoding information that specifies the unit of the georeference and the type of coordinate such as spherical or planar.

There are two basic kinds of geocoding information :

For a list of raster file formats supporting geocoding in their header, refer to the section titled Supported File Formats in Raster Manager - Raster File Format Handling.


Setting the Geocoding

The geocoding can be easily set for any attached rasters in the Raster Manager dialog by right-clicking on the raster and selecting the menu item Coordinate System > Select From Library. The Raster Managers Coordinate System column can be used to determine if a coordinate system is already specified for a given raster. Note that the geocoding information is going to be saved to the raster header or the attachment depending on its geo priority value.

Geo Priority

Geo priority is an important concept in Raster Manager.  It determines which source of georeference / geocoding information should be used when multiple sources are available. Raster Manager supports three information sources :



Reprojection is the process of transforming a raster from one coordinate system to another coordinate system.  This allows data sources in different coordinate systems be used together. 


Raster Manager is able to reproject any georeferenced and geocoded raster on-the-fly without changing the raster file's coordinate system.

The reprojection can be done by simply unchecking the option Inherit GeoCS from Model. Note that the destination coordinate system is always the coordinate system of the model. If the model has no coordinate system, the raster will not be reprojected. Most of the time, the reprojection of a raster will move the raster to another location. 


Performance Tip : Creating a reprojected version of a raster on disk is more efficient than reprojecting the image on-the-fly.  Note that Bentley Descartes is required for this.


Domain Of Validity

Some geographic coordinate systems, meaning those coordinate system with no Map Projection information, and all reprojected coordinate systems have a validity zone.  This is a  zone on the earth for which the coordinate system is valid. For example, some projected coordinate systems can only be used for areas in North America, while others can only be used for European regions.

When reprojecting a raster which is covering a region greater than the validity zone of the destination coordinate system, Raster Manager will automatically clip the reprojected raster so that only the area of the raster in the destination coordinate system's validity zone be displayed. The pictures below show the clipping that is applied to a world image when reprojected to a coordinate system whose validity zone is not the whole world.


Unreprojected World Image

Raster Manager - Unreprojected World Image 


Clipped, Reprojected World Image

Raster Manager - Reprojected World Image

See also

 Assigning A Geographic Coordinate System 

 Reprojecting to a new Geographic Coordinate System   

Other language sources

 Original Author:Tim Hickman