Mathematica Import/Export Format

SDTS (.ddf)

SDTS GIS format.
Geographic information standard used by the U.S. Geological Survey.
Used for archiving and exchanging maps and map data.
SDTS is an acronym for Spatial Data Transfer Standard.
Based on ISO 8211.
U.S. Federal Information Processing Standard.
An SDTS transfer archive consists of multiple .ddf files combined in a .tar.gz file.
The file extension .ddf is derived from Data Descriptive File.
Binary format.
Contains digital line graphs (DLG) or digital elevation models (DEM).
Digital line graphs are vector data commonly used for maps.
Digital elevation models are stored as a raster of elevation values.

Import can read the DLG and DEM content of SDTS.

IMPORT

Import["dir", "SDTS"] or Import["dir"] imports an entire SDTS directory and returns a combined rendering of all graphics layers.

Import["fileCATD.ddf"] explicitly specifies the main .ddf file of an SDTS bundle to be imported.

Import["dir"] returns a Graphics object.

Import["dir", "elem"] imports the specified element from an SDTS file.

Import["dir", {"elem", "sub_a", "sub_b", ...}] imports a subelement.

Import["dir", {{"elem₁", "elem₂", ...}}] imports multiple elements.

See the reference pages for full general information on Import.

ELEMENTS

General Import elements:

	"Elements"	list of elements and options available in this file
	"Rules"	full list of rules for each element and option
	"Options"	list of rules for options, properties and settings

Data representation elements:

	"Graphics"	all layers combined into a single Graphics object
	"GraphicsList"	list of graphics representing the layers of an SDTS archive
	"Data"	graphics primitives for each layer
	"ElevationRange"	range of elevation coordinates, typically given in meters
	"SpatialRange"	range of geographic coordinates, typically given in decimal degrees

Import by default uses the "Graphics" element for SDTS bundles.

Import with element "Graphics" gives the combined graphics contents of an SDTS archive as a Graphics object, rendering DEM data as a ReliefPlot.

Data representation elements:

	"LayerNames"	labels for each layer, given as a list of strings
	"LayerTypes"	SDTS data types for each layer

OPTIONS

General rendering options:

Background	None	background color
DataRange	Automatic	the range of latitude and longitude values to assume for the data
ImageSize	Automatic	overall size of the image

DEM rendering options:

BoxRatios	Automatic	effective 3D bounding box ratios
ColorFunction	"Topographic"	how to determine the color of surfaces
DataReversed	False	whether to reverse the order of rows
LightingAngle	Automatic	the effective angle from which simulated illumination is taken to come

Import options:

	"DefaultElevation"	0	elevation setting for areas not covered by the file
	"DownsamplingFactor"	1	integer factor by which the amount of DEM data in each horizontal dimension is reduced on import

Rendering options:

"FaceColors"	Automatic	colors used to render polygon layers
"VectorColors"	Automatic	colors used for points and lines
"LayerSelection"	All	layers to be rendered, given as a list of layer names or indices