The extract raster DEM functionality allows the user to create a raster DEM (i.e. : an image whose pixels contain elevation data) from a region of a Scalable Terrain Model (i.e. : STM).

Here is a short video showing the extraction of a raster DEM and the attachment of the generated raster DEM in Raster Manager.

 

Usability tip : As the video shows, the region of the STM from which the raster DEM need to be extracted cannot be too large. So using a more precise region (e.g. : road corridor, terrain not rectangular) will optimize the chance of being able to extract the contours for the desired region in one pass.

File formats

The extract raster DEM functionality supports a few different file formats for storing the DEM information.

• Internet TIFF
• Internet TIFF 64 bits
• Erdas IMG
• TIFF
• GeoTIFF

Performance Tip : Use the Internet TIFF file format for best performance and interoperability with MicroStation`s Raster Manager,

There are also two pixel types that are available for storing DEM elevation in the raster DEM.

• 16 bits signed integer number
• 32 bits floating point number

Precision Tip : Use the 32 bits floating point number for increase precision and if you want to keep the digit after the decimal (e.g. : centimeter precision).

For pixel whose center doesn`t overlap any terrain data (i.e. : outside the boundary of the STM) the no data pixel value (i.e. : the pixel value used by default) is -32767.

The vertical unit of the DEM raster is the same as the vertical unit of the STM.