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  ChartTiff Topographic Maps
All ChartTiff Topographic Map Tiff files are enhanced to the ChartTiff format with additional tags.
ChartTiff is a superset of the GeoTiff standard.

The following Tiff tags are included.
They are extensions of the Tiff 6.0 specification:

Tag Name Description
33550 ModelPixelScaleTag X, Y and Z pixel scale in map linear units per pixel.
33922 ModelTiepointTag IJK , XYZ pixel/Coord sets
First 4, SW, NW, NE, SE Define the NEATLINE
34735 GeoKeyDirectoryTag Geo Key Directory header information
34737 GeoAsciiParamsTag ASCII Valued keys

The following GeoTiff keys are included in the GeoKeyDirectory:

Tag Name Description
1024 GTModelTypeGeoKey Coordinate System
1025 GTRasterTypeGeoKey 1 = Raster Pixel Area
3072 ProjectedCSTypeGeoKey Projected Coordinate System
3073 PCSCitationGeoKey ASCII reference to published documentation
4099 VerticalUnitsGeoKey Vertical Datum Units—Feet or Meters

 The following ChartTiff keys have been added to the GeoKeyDirectory:

Tag Name Description
47002 ChartSource Source of the map ie. USGS
47004 ChartSourceDate Source date of map data
47005 ChartCorrDate Last Revision Date of map
47017 ChartContourInterval Contour interval Multiplied by 10,
see VerticalUnitsGeoKey for units

 Additional Related Documentation: