<html> <head> <title>Leveller --- Daylon Leveller heightfield</title> </head> <body bgcolor="#ffffff"> <h1>Leveller --- Daylon Leveller Heightfield</h1> Leveller heightfields store 32-bit elevation values. Format versions 4 through 7 are supported with various caveats (see below). The file extension for Leveller heightfields is "TER" (which is the same as Terragen, but the driver only recognizes Leveller files).<p> Blocks are organized as pixel-high scanlines (rows), with the first scanline at the top (north) edge of the DEM, and adjacent pixels on each line increasing from left to right (west to east).<p> The band type is always Float32, even though format versions 4 and 5 physically use 16.16 fixed-point. The driver autoconverts them to floating-point.<p> <h2>Reading</h2> <tt>dataset::GetProjectionRef()</tt> will return only a local coordinate system for file versions 4 through 6.<p> <tt>dataset::GetGeoTransform()</tt> returns a simple world scaling with a centered origin for formats 4 through 6. For version 7, it returns a realworld transform except for rotations. The identity transform is not considered an error condition; Leveller documents often use them.<p> <tt>band::GetUnitType()</tt> will report the measurement units used by the file instead of converting unusual types to meters. A list of unit types is in the <tt>levellerdataset.cpp</tt> module.<p> <tt>band::GetScale()</tt> and <tt>band::GetOffset()</tt> will return the physical-to-logical (i.e., raw to realworld) transform for the elevation data.<p> <h2>Writing</h2> The <tt>dataset::Create()</tt> call is supported, but for version 7 files only.<p> <tt>band::SetUnitType()</tt> can be set to any of the unit types listed in the <tt>levellerdataset.cpp</tt> module.<p> <tt>dataset::SetGeoTransform()</tt> should not include rotation data.<p> As with the Terragen driver, the <tt>MINUSERPIXELVALUE</tt> option must be specified. This lets the driver correctly map from logical (realworld) elevations to physical elevations.<p> Header information is written out on the first call to <tt>band::IWriteBlock</tt>.<p> <h2>History</h2> v1.2 (Jul 17/07): Added v7 and Create support.<p> v1.1 (Oct 20/05): Fixed coordsys and elev scaling errors.<p> <h2>See Also:</h2> <ul> <li> Implemented as <tt>gdal/frmts/leveller/levellerdataset.cpp</tt>.<p> <li> <a href="http://www.daylongraphics.com/products/leveller/dev/index.htm"> Leveller SDK</a>, which documents the Leveller format.<p> </ul> </body> </html>
