DIGITAL ELEVATION DATA AND GIS PROJECTS
Robert De Sawal U.S.GeologicalSurvey PO BOX 25046,MS-520 Denver,Colorado 80225 303-202-4804 fax 303-202-4504 e-mail rfdesawal@usgs.gov
ABSTRACT ...
Digital elevation model
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[edit] Digital noise
When data is transmitted, or indeed handled at all, a certain amount of noise enters into the signal.
Digital Elevation Models
The most basic and interesting geographical data type is the digital elevation model (DEM).
Digital InterPlot
Technical Requirements
Plot server
Windows NT 4.0 Service Pack 4 or greater, Windows 2000 Server Service Pack 3 or greater or Windows Server 2003
Microsoft Data Access Component (MDAC) 2.5 or greater.
Digital Elevation Models
Opening a Landsat Triplicate in Multispec
Sources of Geographic Images ...
Compared to common analog RF-output GNSS signal generators, this digital output GNSS signal generator has the advantage of a deterministic data output.
Digital Photogrammetry and Image Services
We offer Digital Photogrammetry and Image Services, by using the latest digital photogrammetric technology and software.
DigitalGlobe
Real world imagery solutions
With DigitalGlobe's advanced commercial satellite constellation and aerial networks, incorporating high-resolution earth imagery into GIS projects or applications has never been easier.
Digital Orthophotography - A photo-quality digital image of surface features in their geometrically corrected, true map projection. The orthorectification process ties each pixel in a digital image to its true earth location.
Digital Orthophoto Mosaic
The mosaic below covers part of Jasper National Park in Alberta, Canada.
digital terrain model or DTM may actually be a more generic term for any digital representation of a topographic surface, but it is not so widely used
the DEM is the simplest form of digital representation of topography and the most common ...
Purpose: DEM's can be used as source data for digital orthophotos, and, as layers in geographic information systems, for earth science analysis.
Chapter 1: Understanding Digital Maps
When you want to use a paper map, first you need to unfold it. You need a large space, probably an entire table, to do this.
Ensuring the long term accessibility and usability of records stored as digital images is largely dependent on how digital imaging systems are designed, implemented, managed, and migrated.
Content Standard for Digital Geospatial Metadata
See Also: FGDC
[standards] A publication authored by the FGDC that specifies the information content of metadata for digital geospatial datasets.
Digital Image Processing
To be effective in management decisions, a geographic information system requires timely, accurate update of many of its spatial data elements.
DIGITAL LEVELS
7-3. The level has been advanced, along with other survey equipment, into using electronic measurements.
digital elevation model
The digital cartographic representative of the surface of the Earth or a subsurface feature through a series of three-dimensional coordinate values: a continuous variable over a two-dimensional surface by a regular array ...
DIGITAL ELEVATION MODELS (DEMs)
A DEM is an image that contains topographic information. These are available for free download (at a low 1 km resolution), or at higher resolutions for a cost.
digital map library : A series of directories and subdirectories designed to uniformly organize a collection of spatial data. Map libraries organize geographic data spatially as a set of tiles and thematically as a set of layers.
Digital Elevation Model (DEM): A digital representation of a continuous variable over a two-dimensional surface by a regular array of z values referenced to a common datum. Digital elevation models are typically used to represent terrain relief.
Digital Exchange Format (DXF)
DXF is an external format for transferring files between computers or between software packages. It is produced by Autocad.
Digital Data Working Group
HTML Created: Jan 98
Published by the Resources Inventory Committee ...
digital image -- a two-dimensional array of regularly spaced picture elements (pixels) constituting a picture.
digital volume -- a three-dimensional array of regularly spaced volume elements (voxels) constituting a volume.
Digital elevation model (DEM)
A topographic surface arranged in a data file as a set of regularly spaced x, y, z coordinates where z represents elevation.
Digital Elevation Model (DEM) A digital representation of a topographic surface. Elevation values may be stored in a regular grid of values, one for each cell, a regular lattice of points or in a 'triangulated irregular network' (TIN) of points.
Digital Data: Any data in computer readable format usually stored on magnetic tape, CD, disk or hard drive.
[edit] Digital library metadata
There are three categories of metadata that are frequently used to describe objects in a digital library:[16] ...
Digital Elevation Models (DEMs) and Viewing Modes
In recent years, contour values have been digitized allowing them to be manipulated into versatile displays of topographic data as digital elevation models or DEMs.
Digital preservation differs from traditional archiving. Archives traditionally preserve physical objects (e.g. paper, photographs, microfilm) which carry information.
Digital orthophotos require several types of inputs to produce an orthogonally rectified image from the original perspective image captured by the sensor. These inputs are the following: 1) the unrectified raster image scanned from the diapositive or ...
Digital Photogrammetry
Detailed discussion of all issues related to the practical use of digital photogrammetry.
Digital Vision/Getty Images
The Sahara Desert is located in the northern portion of Africa and covers over 3,500,000 square miles (9,000,000 sq km) or roughly 10% of the continent (image).
Digital data already in tabular form integrate into the GIS database in two very important ways. First, they form the basis for GIS feature attributes. In this case they must be linked somehow to the objects forming the spatial geometry.
Digital Map Publishing, Geospatial Solutions, March 1, 2005.
Likened to Adobe Acrobat for GIS, Esri ArcGIS Publisher creates digital map files that can be shared (using ArcReader) with a wide range of users, including those who do not have or use GIS.
Digital photo base maps, scanned paper maps, and other raster maps are very effective base layers for internet map servers or standalone desktop analysis systems.
digital formats A specific logical format in which digital data is maintained. This is often software specific.
digital map A map maintained in a computer readable electronic format.
Digital Geographic Information Exchange Standard
DILI
Digital Index of Land Information ...
Digital divide
Digital Nervous System "The digital processes that enable a company to perceive and react to its environment, to sense competitive challenges and customer needs, and to organize timely responses.
Digital Elevation Model
Descriptive Data
Tabular data describing the geographic characteristics of map features. Can include numbers, text, images, and CAD drawings about features.
Digital map storage is rapidly moving toward spherical referencing that uses latitude and longitude in decimal degrees for internal storage and on-the-fly conversion to any planar projection.
Digital Elevation Model (DEM)
A file containing elevation points that have been sampled at regularly spaced intervals. A DEM is used for the generation of contours, shaded relief, 3-D terrain models and elevation profiles.
Differential GPS (DGPS) ...
Digital Navigational Chart (DNC) certified
The DNC is a database of electronic charts created by NGA and its predecessors over the last 15 years.
Digital Chart of the World (DCW) - A digital cartographic database of the World, developed by the US Defense Mapping Agency (DMA, which is now part of National Geospatial-Intelligence Agency (NGA)), with the cooperation of Australia, ...
Digital to Analog (converter)
DAAC
Div. des archives audiovisuelles et cartographiques, Archives nationales du Canada; Distributed Active Archive Center ...
A digital orthophoto demonstration is available free from the SCO to download.
Published Resources
We suggest the following books for introductions to the basics of aerial photography.
The digital representation and manipulation of geographic concepts raise a number of fundamental research issues, many of which, though long-standing in traditional disciplines, have been re-energized by the development of GIS.
The DTED digital terrain model was applied in the calculations. This model was made by the NIMA (National Imagery and Mapping Agency), and has the resolution of 30"x30".
We have a digital library of local, state and federal digital-map resources and coverages, including public-school locations, HAZ-MAT locations, FEMA floodway maps, etc. Our capabilities to find, develop and use new data coverages are extensive.
Downloads digital raster graphics from Microsoft TerraServer. Note that srs will need to be changed to a projection that is appropriate for your region.
REQUIRED PROGRAMS
r.in.wms requires the following programs to work: ...
Even after digital computers became generally available, results were far from uniform. Many algorithms for Schwarz-Christoffel mapping suffered from low efficiency, limited precision, or instability, i.e.
Figure 3a. Digital revision of 1:100,000-scale digital line graph data to produce a 1:500,000-scale New Jersey State base map. Paneling and generalization are shown in three stages from 1:100,000 scale to 1:250,000 scale to 1:500,000 scale.
Creating 3-D digital elevation models (DEMs) from vectorized contour lines is an automatic, but computer-intensive, process. An interpolation algorithm is used to fill the space with elevation values using contours. ...
coverage: A digital version of a map forming the basic unit of vector data storage in ARC/INFO.
Preparation of the digital 3D topographic maps.
Raster to Vector conversion of topographic maps is conducted in CAD based softwares such as AutoCAD, Microstation etc.
DLG stands for digital line graph, a form of digital map developed by the United States Geological Survey. DLGs supply users with the digital version of information printed on USGS topographical quadrangle maps.
The introduction of digital noise. This is the process the Department of Defense (DoD) uses to add inaccuracy to GPS signals to induce Selective Availability.
Doppler-aiding ...
optical disk A digital data storage technology that uses optical media to store information. Optical disks are slower, but store more data and cost less per unit of stored data than magnetic disks.
Digital Exchange Format (DXF)
ASCII text files defined by Autodesk, Inc. Originally used in CAD, now showing up in a third party GIS software.
 See also: Information, GIS, Geographic, Model, Software
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