heberlei@iris.ucdavis.edu (Todd) (03/09/89)
I am looking for some digital topological data. I would like to create a 3-D image of some landscape (ie. a mountain range). Does anyone know where I can obtain this data? Is it Public Domain or has it been privatized? Answers or leads would be very much appreciated! Thanks, Todd Heberlein Division of Computer Science University of California Davis, Ca. 95616 heberlei@iris.ucdavis.edu 128.120.57.20
eugene@eos.UUCP (Eugene Miya) (03/09/89)
Do you mean topographic or topological?
The former tends to cost some money since it is based on the real world
and real world people have had to digitize it. The latter gets generated
by mathematicians during some of their studies. You can't always be too sure.
Another gross generalization from
--eugene miya, NASA Ames Research Center, eugene@aurora.arc.nasa.gov
resident cynic at the Rock of Ages Home for Retired Hackers:
"Mailers?! HA!", "If my mail does not reach you, please accept my apology."
{uunet,hplabs,ncar,decwrl,allegra,tektronix}!ames!aurora!eugene
"Post follow ups. Contribute to network noise."bw@hpcvlx.HP.COM (Bill Wilhelmi) (03/15/89)
I don't know if you have received any good responses yet,
but I just received a package of information from the USGS
regarding their digitized mapping services. Apparantly,
they have many FORTRAN programs that process digital mapping
data for various uses. Among these are their Digital Line Graph
series.
The USGS maintains what they call a "National Digital Cartographic
Database". To quote from "Digital Line Graphs from 1:24000-Scale
Maps, Data Users Guide" (which you can order from the USGS:
Current data collection from 1:24000-scale and other large-scale
maps is exclusively directed toward producing fully topologically
structured level 3 DLG data referred to as DLG-3. The DLG-3
concept is based on graph theory in which a two-dimensional diagram
is expressed as a set of nodes (topologically significant points),
lines, and areas in a manner that explicitly expresses logical
relationships. Applied to a map, this concept is used to encode
the digital data with the spatial relationships between map
elements which are obvious when the map is examined visually.
The spatial realationships include such concepts as adjacency and
connectivity between features on the map. The abstraction of the map
data according to the rules of graph theory preserves the spatial
relationships inherent in the map graphic and creates a logical
and consistent data file structure for computer processing. A
digital file of catographic or geographic data that maintains the
spatial relationships inherent in the map is called a topologically
structured data file. A toplologically structured data file can
support simple graphic applications, such as plotting streams and roads
for base maps, as well as more advanced applications, such as
computations and analyses involving areas and lines and their spatial
relationships.
The fees for the software (FORTRAN compiled under IBM JCL and some PC
software) is available for nominal handling and materials fees from
the USGS. You might want to write the USGS and ask for catalogs
and information about the National Mapping Program.
Bill Wilhelmi
Hewlett-Packard - Corvallis Workstation Operation
1000 NE Circle Blvd. Corvallis, OR 97330
ARPA: bw%hp-pcd@hplabs.HP.COM
UUCP: {ihnp4,cbosgd,allegra,decvax,gatech,sun}!hplabs!hp-pcd!bw