[Gdal-dev] GeoQuadTree - an open format for storing georeferenced images

[Brent Fraser]

Simon,

    VTP http://vterrain.org/ (to paraphrase Schuyler Erle "the best kept secret open source geo app on the net") uses libmini ( http://www.stereofx.org/terrain.html) an open source library for tiling images (textures) and elevations models ("height fields").

    In the VTP implementation, the authoring tool VTBuilder takes a user-specified set of images and creates a tileset.  the Tileset has an "INI" file to describe it's properties:

[TilesetDescription]
Columns=12
Rows=16
LOD0_Size=1024
Extent_Left=370826.6795802761
Extent_Right=391921.9795802761
Extent_Bottom=2408667.927330024
Extent_Top=2436626.127330024
CRS=PROJCS["NAD83 / UTM zone 4N",GEOGCS["NAD83",DATUM["North_American_Datum_1983",SPHEROID["GRS 1980",6378137,298.2572221010002]],PRIMEM["Greenwich",0],UNIT["degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",-159],PARAMETER["scale_factor",0.9996],PARAMETER["false_easting",500000],PARAMETER["false_northing",0],UNIT["metre",1]]

>From the libmini doc, the tiles "can be saved in the PNM format (PGM/PPM for grayscale/RGB images), but the native DB format of the Mini Library should be preferred."

The tile files are named (for the db format):
    tile.0-0.db         - first row, first column, highest level of detail
    tile.0-0.db1 
    tile.0-0.db2 
    tile.0-0.db3       - first row, first column, lowest level of detail
    tile.1-0.db         - second row, first column, highest level of detail
        :

Brent Fraser

  . Could somebody outline the solution used by the Virtual Terrain project?

  Cheers,

  Sy

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