Index of Resources:
Status maps present the process of data creation and conversion: Soils Survey of Spokane County, National Wetlands Inventory, ...
World Data Bank I & II (CIA 1970s) public domain (reproduction
cost)
Defense Mapping Agency (now National
Imagery and Mapping Agency): Digital Chart of the World (CD-ROM)
1:1,000,000 (cheap); lots of world coverage; used as the prototype
for later Vector Product Format materials
from NIMA.
lots of world coverage in Global Change Database; Global
Land Information Network
USGS DEM's :
USGS Digital Line Graphs :
Orthophoto
Quads: rectified photography 1 meter cell size (Map Library
has CDs as they arrive)
TIGER replaces DIME (those files are still available for
urban areas); TIGER available at $175/state + $15/county (at CSSCR)
total US coverage $57,785 major emphasis on roads for census blocks
Lots of commercial versions of street networks developed from
TIGER [eg. Delorme Mapping,
selling map products ,ETAK]
Washington DNR holds many layers under its Public Trust doctrine
DNR sells Soils, PLSS, and certain other layers for $50 per township
(plus sales tax...) under a license.
The Washington Clearinghouse
is a part of the NSDI clearinghouse network.
The Olympic Natural Resources Center operates a "subnode".
EOSAT, the US attempt to commercialize a federal program. LANDSAT
scenes $600-3000 depending on size, resolution etc. (market based?)
SPOT Image, a French govt. owned commercial operation, 10m (20
m) for sale 10meter monochrome maybe $700, color (20m) $1400 up.
To transfer the information from one system to another, there
must be some mechanism to encode information so that some other
software can understand it. In addition, the different models
must often be transformed.
The original thinking was dominated by the technology: tape drives
and arms-length transactions. A network of clients and servers
may render all this obsolete...
The case for standards (at
ISO)
Raster formats are not about representation of each cell: that
is almost always binary. (one byte, etc.)
Issue is organization:
GIS example Remote sensing details MAP II (GRASS) Band Sequential all cells for each layer IMGRID Band Interleaved all values for each cell
TIFF (Tagged interchange format), PICT, MPEG, GIF, lots of
industry methods
Attempts to coordinate: The Universal Format to End All Universal
Formats
Raster data compression: run-length encoding, scan line differences,
quadtrees...
Different amounts of topological information: CAD typically
has none, GIS does.
Different graphic primitives - beyond point, line, area
CAD offers curve generation (spline, conics), GIS tends to have
only straight lines
Cartographic "features" (thingies) versus coverages
(whole exhaustive surfaces); big issue of reuse of the "same"
line
Convert one data model (measurement framework) to another.
Raster to vector/ vector to raster translation: lots of options,
none very satisfying... Raster linework [representation of object
boundaries in a raster representation] (different from raster
areas [raster representation of an spatial control framework])
Creation of topology from spaghetti, translation of object definitions
(not easy)
CAD world has de facto standards due to dominance of specific
software packages:
Intergraph Standard Interchange File (SIF) at high end (internal
IGDF)
(Intergraph has recently tried to make their formats open)
Auto-CAD DXF (an ascii format) at low end. [neither have a lot
of structure]
USGS has Digital
Line Graphs (DLG) as a topological format.
Defense Mapping Agency (now part of NIMA)
has a lot of standard
products.
ARC/INFO has an export format (E00), but the internal structures
are proprietary. ArcView has 'shapefiles', another simpler format.
early approach: ODYSSEY (ca. 1978) had a "Global"
description file which preceeded any actual data file. The globals
contains the descriptions of file content and the "information
about the information" (data quality, coordinate reference,
etc.)
Had simple primitives: files of records, fields of int, real,
char, one var. length
SDTS (US National
Standard: FIPS 173) Spatial
Data Transfer Standard generated by National Committee for
Digital Cartographic Data Standards for USGS Working Group on
Data Organization chaired by T. Nyerges, Federal Register Dec
90 Uses ISO 8211 (a self-describing interchange encoding scheme)
as a vehicle. Includes NCDCDS Data
Quality Standard (see Data Quality lectures)
also adopted as an ANSI standard.
DIGEST
the military (NATO) similar to SDTS but just different enough.
adopted by French, UK. Includes a feature based standard and the
Vector Relational Format (originally called VPF) plus a raster/grid
format.
VPF Vector
Product Format: designed for DMA Digital
Chart of the World. Not an exchange standard (though incorporated
as Part C of DIGEST), but a format for direct use of database
from CD-ROM. Original application: Digital Chart of the World
, now used for many DoD products and applications (eg. VMAP)
Open GIS: a consortium
dedicated to interoperability
membership
is mixed...
Emphasis on Interoperability
International Standards Organization (ISO) is trying to generate
a worldwide standard: Technical Committee 211 TC211
European Coordination Group EUROGI,
Australian Coordination Group
Before anyone transfers data, they need information describing
that data. Metadata is 'data about data'. [Implements a 'fitness
for use' situation where the user makes the judgement.]
SDTS includes some issues about metadata, the Data Quality Report
was meant to be available separately to act as metadata. Not really
implemented that way by anyone....
Federal Geographic
Data Committee has published Content
Standard for Geospatial Metadata which provides a guideline
for metadata content. Various states have developed their own
variant or simply adopted the federal guideline. [eg. Montana
GIS site]
NASA has massive data system projects, such as EOSDIS, now ESDIS,
with attention to metadata as a core concept.
Alternative: German ATKIS standard specifies everything
about the database, conformance to expectation.
There have been some massive investments in research on "Digital
Libraries". A fair proportion of this money has gone to spatial
data.
Data transfer (as considered in the earlier systems) shipped a client a whole database, usually in the format of the provider. This role may switch so that the user sends out a request for specific 'objects' in a specific format, and the server extracts them and ships them.
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Version of 18 November 2002
