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Digital terrain model - Wikipedia, the free encyclopedia The data files contain the elevation data of the terrain in a digital format which relates to a rectangular grid. DTMs are used especially in civil engineering, geodesy and surveying, geophysics, geography and remote sensing. A digital terrain model may be used to guide automatic machinery in the construction of a physical model, the relief map. en.wikipedia.org /wiki/Digital_terrain_model   (233 words)

Digital elevation model - Wikipedia, the free encyclopedia A digital elevation model (DEM) is a representation of the topography of the Earth or another surface in digital format, that is, by coordinates and numerical descriptions of altitude. Digital elevation models may be prepared in a number of ways, but they are frequently obtained by remote sensing rather than direct survey. One powerful technique for generating digital elevation models is interferometric synthetic aperture radar; two passes of a radar satellite (such as RADARSAT-1) suffice to generate a digital elevation map tens of kilometers on a side with a resolution of around ten meters. en.wikipedia.org /wiki/Digital_elevation_model   (485 words)

NJDOT - Minimum Guidelines For Aerial Photogrammetric Mapping (Metric) Digital Terrain Model Specifications are for three-dimensional coordinates of points taken in a specified pattern and recorded on a computer-compatible media. The digital terrain model shall be grid, cross section, re-measurement or critical point type, whichever will be specified and applicable to the particular project.  For grid digital terrain models, the maximum spacing shall be fifteen (15) meters, and likewise the same maximum space for cross section, re- measurement or critical points. A digital terrain model for computing earthwork quantities for pay shall not be accepted until at least four (4)  percent of the grid points or of the cross sections have been compared with ground surveyed data and have met specifications requirements. www.state.nj.us /transportation/eng/documents/photogrammetry/Section6.htm   (807 words)

Digital Photogrammetry   (Site not responding. Last check: 2007-11-05) As part of the research, digital orthophotographs were used as a base map for two-dimensional floodplain mapping, and a TIN digital terrain model was developed to aid in three-dimensional floodplain visualization. Digital orthophotograph data were used as a base map as background imagery, as a basemap with which digitize Waller Creek and key stream points, and to estimate building height. Digital terrain model data were used as inputs to a TIN model, and to create the CAPCO TIN used to validate my work in three-dimensional terrain modeling. www.ce.utexas.edu /prof/maidment/grad/tate/study/remote/TermProj.html   (3345 words)

TRIANET | DTM - Digital Terrain Model A digital terrain model represents the relief of the earth’s surface by a set of x,y,z data points where "x" is the horizontal x-position (e.g. DEM of the vegetation surface, DEM of the groundwater surface or DEM of the relief of the earth surface which is also called "digital terrain model". 5.1 A Digital Terrain Model (DTM) of Naxos nibis.ni.schule.de /~trianet/dtm/dtm1.htm   (229 words)

MassGIS - Digital Terrain Model (DTM) Files Datalayer Description Digital terrain models are representations of land surface point elevations. The DTMs available from MassGIS were produced for the processing of the 1:5,000 Black and White Digital Orthophoto images and their related data layers (Elevation Contours, Elevation Points, and Topographic Breaklines). The DTM data points were collected on analytical stereoplotters at a sufficient density to support generation of 3-meter contours conforming to the National Map Accuracy Standards (+ or - 1.5 meters). www.mass.gov /mgis/dtm.htm   (640 words)

USGS Digital Elevation Model (DEM) Data Digital elevation models are typically derived from USGS topographic maps. Digital Elevation Models are data sets of regularly sampled topographic elevations typically derived from USGS topographic maps. Digital elevation models are preferable to digitized contour maps, such as some DLG files, because DEM models use a uniform data spacing. www.bossintl.co.uk /html/rivercad_dem_data.html   (859 words)

digital terrain model, dtm software   (Site not responding. Last check: 2007-11-05) Surface modeling results are quickly computed and instantaneously displayed onto the screen prior to adding the computed surface to the drawing. The DTM Module utilizes virtual memory, so the size of a surface model is limited only by the available hard disk space. The DTM Module will take a 2D polyline drawn in plan view and then convert this polyline into a 3D polyline which conforms to the computed surface model, thereby creating a section view of the surface along that polyline. www.bossintl.com /html/rivercad-dtm.html   (854 words)

Suitable digital elevation model DTM (digital terrain model) is mathematically defined as spatial distribution of heights that are described by continuous and regionally (within the segments) smooth surface. In the praxis good approximation of the DTM is digital elevation model (DEM) that is recorded as two-dimensional discrete matrix of data heights that is more common known as grid structure. They can be acquired directly, for instance photogrammetrically from stereo model or indirectly, for example from analogue cartographic data, satellite images, by surveying, etc. Interpolation is also not necessary in the cases if data source is very precise and high density, and especially if the data is acquired directly into regular grid (DEM). www.gisdevelopment.net /technology/tm/tm003a.htm   (1008 words)

Digital Terrain Models (DTMs) Europe DTM 2.5 enables a rapid estimate of regional terrain corrections for gravity studies and determination of regional contributions to the isostatic correction. South America DTM 3 is a 3' x 3' grid for the South American region from 100°W to 25°W and 60°S to 25°N. The grid is based on the best gridded terrain models currently available with the addition of a vast number of height measurements not used in DTMs before. South America DTM 3 enables a rapid estimate of regional terrain corrections for gravity studies and determination of regional contributions to the isostatic correction. www.getech.com /data/dtms.htm   (317 words)

Introduction to GIS: 4   (Site not responding. Last check: 2007-11-05) A DTM may be understood as a simplest digital representation of a portion of the earth's surface, but it is perhaps the most commonly used. The activity of modelling and processing digital terrain data may thus be regarded as a system component of GIS that is functionally disparate from modelling 2-D data, yet needs to be closely linked to other processing functions of GIS (e.g. The quality of the final digital terrain model is determined by; the frequency, accuracy and distribution of the sample points, and the adequacy of the interpolation method used to generate the estimates at the unknown locations. www.geog.nottingham.ac.uk /~mjm/teaching/general/gis4.htm   (2643 words)

Space Imaging   (Site not responding. Last check: 2007-11-05) A digital terrain model (DTM) is a digital file consisting of terrain elevations for ground positions at regularly spaced horizontal intervals. Digital terrain products may be used in the generation of three-dimensional graphics displaying terrain slope, apsect (direction of slope), and terrain profiles between selected points. Non-graphic applications such as modeling terrain and gravity data for use in the search for energy resources, calculating the volume of proposed reservoirs, and determining landslide probability have also been developed. www.spaceimaging.com /products/digital_terain_models.htm   (171 words)

Aerial Archive - Visualization The easiest way is to digitize contour lines from a map and and let computer software calculate the terrain model. Another possibility is to transfer the terrain data into 3D modelling software, where they can be combined with modelled 3D reconstructions of the archaeological features. Digital terrain model with reconstructed archaeological features of the Slavic settlement. www.univie.ac.at /Luftbildarchiv/archiv/aa_vis.htm   (517 words)

Washington County, MN - Surveyor Metadata Contours Uses of the digital 2 foot contours, digital terrain model data, and basic planimetric features within Washington County include: creation of preliminary grading plans, hydrologic analysis, land use planning, zoning enforcement, law enforcement applications, surface water analysis, flood plain management, road design, and the updating of GIS parcel base mapping. A digital terrain model, (DTM), was created using break lines along changes in slopes and a mass point grid of 50’ for areas requiring contours. Digital elevation model, (DEM), data was created using break lines along major changes in slopes and a mass point grid of 50’for use in developing the orthophotos in areas not requiring contours. www.co.washington.mn.us /info_for_residents/survey_and_land_management_division/survey_unit/metadata_for_digital_contours   (1627 words)

Origin Point, Inc. Digital Terrain Modeling Report The projection of roads onto the DTM and the 3D reconstruction of the PPP structure are discussed. In this case, a 10’ x 10’ grid spacing for the terrain in the immediate area of the PPP and a 50’ x 50’ grid spacing for the remainder of the study area are used. This surface model of the terrain is made up of a series of triangular faces. www.originpointinc.com /dtm.htm   (1232 words)

Digital Terrain Model: Elevation Extraction and Accuracy Assessment   (Site not responding. Last check: 2007-11-05) Prior to using DTMs for various applications, it is prudent to analyze errors of the extracted DTMs to ensure that they meet the required accuracy standards. DTM data, for about 500 points for a 20 × 50 m grid, were collected using different modes (static, fast static, stop-and-go kinematic) of global positioning system (GPS) surveys on a study area of approximately 0.7 km × 1.0 km in Lavonia, Georgia. Two stereo models at a scale of 1:3,000 have been used to capture DTM and planimetric data on the same study area using three different digital and one analytical photogrammetric systems. www.pubs.asce.org /WWWdisplay.cgi?9701461   (240 words)

[No title]   (Site not responding. Last check: 2007-11-05) Digital terrain model of the Seville area of Spain produced from SPOT-PA imagery [1:100000] scale, using the Digital-Vision/Laser-Scan ITG stereo DTM creation facility. These are either output producing a digital disparity model, which can be further processed using tools like disp2ddm or they are passed to the camera model which transforms them from image space to ground space, producing an ungridded array of (x,y,z) co-ordinates in a geocentric co-ordinate system. In addition to producing DTM's, a pipeline generator gti is provided which generates orthoimages using the DTM generated by the itg subsystem and one of the images (used by itg to generate the DTM. chasseur.usc.edu /pups/projects/itg.html   (630 words)

Digital Terrain Modelling - G516 Presentation   (Site not responding. Last check: 2007-11-05) A digital terrain model is a digital representation of part of the earth's surface. Digital elevation data may be derived from ground survey, photogrammetry or cartographic data capture. The accuracy of a DTM depends on the accuracy of its source data and on the model resolution. www.geog.ubc.ca /courses/geog516/notes/dtm.html   (465 words)

ITC —Digital Terrain Model Extraction, Processing and Parameterization in Hydrology   (Site not responding. Last check: 2007-11-05) Models used range from very simple one-dimensional to complex models involving many parameters and are capable to simulate a 4-D environment (x,y,z and time). DTM: what is a DTM, use of a DTM in hydrology and relevant parameters that can be obtained from a DTM, difference between DTM and Digital Surface Model. DTM construction-modification using active sensors like SRTM and Lidar, converting ranges to points on the terrain to terrain elevations, filtering techniques and point interpolation procedures. www.itc.nl /education/programme_levels/module_descriptions/M06-WREM-101.asp   (582 words)

ComputaMaps - Imprensa   (Site not responding. Last check: 2007-11-05) The DTM was compiled by ComputaMaps and will be used for orthorectification of satellite imagery as well as for input to terrain visualisation and planning tools. The terrain model was interpolated from digital map data, captured from 1:50000 scale topographic mapping supplied by the Chief Directorate: Surveys and Mapping. The DTM was generated on a degree-square basis using the most advanced gridding software available for creating DTMs from contour and spot height data. www.computamaps.com /pt_press_06-04-2001.php   (564 words)

The Jerusalem Archaeological Park - homepage   (Site not responding. Last check: 2007-11-05) The first step towards creating the real-time visual simulation model of the Herodian Temple Mount was to build the digital terrain. This 'stack' of data was used as the basis for a triangulated mesh surface model of the terrain. A second map of ancient Jerusalem (Ben-Dov's) was digitized, composited with the topography map, and used to outline and extrude the ancient city walls. www.archpark.org.il /netscape/virtual2.shtml   (214 words)

Automatic DTM Generation   (Site not responding. Last check: 2007-11-05) The derivation of surface models or Digital Terrain Models (DTMs) from photographs or digital images is one of the main tasks of photogrammetry. Therefore the automation of DTM generation from aerial photographs and satellite images is urgently needed. The DTM generation is done with a hierarchical matching procedure in a coarse-to-fine approach. www.p.igp.ethz.ch /p02/projects/autodtm/p1.html   (225 words)

GEO World - May 2003 - Use LIDAR to Generate Digital Terrain Model Data   (Site not responding. Last check: 2007-11-05) To understand LIDAR DTM processing, it's important to understand that the raw (unfiltered) LIDAR dataset consists of distance and angle measurements to the reflective surface beneath the airborne platform. To develop a "bare-earth" DTM, the LIDAR ground points must be separated (classified) and extracted from the DSM. The steps required to develop an adequate digital terrain elevation model are a function of many factors, including the type of vegetation, the density of the tree canopy, the density of the dataset, the LIDAR spot size, whether multiple returns are available and whether the data were collected during "leaf-off" or "leaf-on" conditions. www.geoplace.com /gw/2003/0305/0305ldr.asp   (910 words)

ArchitectureWeek - Tools - Hybrid Digital/Manual Site Drawings - 2002.0828 One approach to drawing a site development in 3D is to first plot the DTM in a grid pattern onto a sheet of Mylar and then draw trees and buildings by hand. The same model, viewed from a low angle, was used to generate quick study drawings for the campus buildings. The campus model, viewed from a low angle, was used to generate quick study drawings for the campus buildings. www.architectureweek.com /2002/0828/tools_1-2.html   (811 words)

Surdex   (Site not responding. Last check: 2007-11-05) The steps required to develop an adequate digital terrain elevation model are a function of many factors, including the type of vegetation, the density of the tree canopy, the density of the data set, the LIDAR spot size, whether multiple returns are available and whether the data were collected during “leaf-off” or “leaf-on” conditions. This sampling of the terrain features results in over-collection of elevation points in flat areas and under-collection in areas of sharp breaks, such as ditches and small streams. The DTM may also be gridded at a nominal post spacing and delivered as a digital elevation model (DEM). www.surdex.com /html/surdex_news.asp?id=280   (1719 words)

Technical notes of the digital terrain model The interpolation or extrapolation model used to generate the DTM, depends on the final application. For instance a DTM of 100 meters per node can be produced with maps of different scales, 1/50,000, 1/100,000, 1/250,000, 1/500,000. The DTM are delivered in any of the projections or references of the map. www.geo3d.com /dtm.htm   (654 words)

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