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DTM by M. Varshosaz
Digital Terrain Models by M. Varshosaz
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An introduction to DTM
Overview of your syllabus Definition Applications Overview of DTM tasks Generation Manipulation Interpretation Visualizations Digital Terrain Models by M. Varshosaz
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Definition:
A statistical representation of the
continuous surface
of the ground by a large number of selected points with known X, Y, and Z coordinates in an arbitrary co-ordinate field.
Provide the means for representing the continuous surface in a digital form using
a finite amount of storage
. Provide the means for representing the
earth’s surface in the computer
.
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Terminology
Digital Terrain Model (DTM).
Digital Elevation Model (DEM).
Digital Height Model (DHM).
Digital Ground Model (DGM).
Digital Terrain Elevation Data (DTED).
Digital Surface Model (DSM).
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Terminology
DEM (Digital Elevation Model): Generally refers to a regular array of elevations (squares or hexagon).
The term is in widespread use in the USA.
DHM (Digital Height Model): Similar as DEM but less commonly used.
The term originated in Germany.
DGM (Digital Ground Model): More emphasis on the digital model of the solid/continuous surface of the earth.
The term in is general use in the UK.
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Terminology (cont.)
DTM (Digital Terrain Model): More complex concept involving elevations and other GIS features (e.g., rivers, ridges, break lines, etc.).
It encompasses terrain relief, planimetric, and derived data (slope, aspect, visibility, etc.).
DTED (Digital Terrain Elevation Data): Term used by the US National Imaging and Mapping Agency (NIMA) formerly known as the Defense Mapping Agency (DMA).
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Terminology (cont.)
DSM (Digital Surface Model): The previous terms usually refer to bare terrain models.
DSM refers to digital models including features above the surface of the earth (e.g., buildings).
Very important for ortho-photo generation.
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DTM synonyms: conclusion
Most widely used are DTM and DEM To define a DTM need: A number of sample points which can define earth with a given degree of accuracy
(DATA)
A mathematical model filling the gaps between the sample points Data and model
(MODEL)
Data and model stored and worked in digital Digital Terrain Models by M. Varshosaz
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DEM products
Slope angle Slope aspect Slope convexity Slope length Hillshading 3D display Digital Terrain Models by M. Varshosaz
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DTM Application Domains
Civil Engineering: Cut-and-fill problems involved with road design.
Site planning.
Volumetric calculations in building dams and reservoirs.
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(Rail) Road design
Horizontal alignment Digital Terrain Models by M. Varshosaz
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Conventional (rail)road design
Longitudinal Profile (vertical alignment) Digital Terrain Models by M. Varshosaz
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Conventional (rail)road design
Cross Sections cut & fill volumes Digital Terrain Models by M. Varshosaz
Concept of
SCO P 15
(Rail)road design with DTM
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DTM Application domains (cont.)
Earth Sciences: Drainage basin network development and delineation.
Hydrological run-off modeling.
Geo-morphological simulation and classification.
Geological mapping.
Generating slope and aspect maps.
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Applications of DTM (cont.)
Analysis and interpretation of terrain morphology A vertical view of a computed drainage system Digital Terrain Models by M. Varshosaz
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DTM Application Domains
Planning and Resource Management: The management of natural resources. Site location.
Support of image classification in remote sensing by DTM derivatives.
Geometric and radiometric correction of remote sensing images Wind flow and pollution dispersion models.
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Monitoring waste deposits comparing volumes under DTM in different times
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100 m
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DTM Application Domains
Military Applications: Consumers and producers (e.g., NIMA).
End objectives are very specialised and demanding.
Inter-visibility analysis for battlefield management.
3-dimensional display for weapons guidance systems and flight simulation.
Radar line-of-sight analyses.
Topographic mapping.
Surveying and Photogrammetry: They are important sources for DTM generation.
DTMs are useful for various surveying and photogrammetric activities: Ortho-photo production, M. Varshosaz
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Applications of DTM (cont.)
Military service 3D visualization and Flight simulation Intervisibility analysis Weapon guidance etc Digital Terrain Models by M. Varshosaz
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DTM application areas (cont.)
Surveying and photogrammetry Orthophoto production Topographic mapping Digital Terrain Models by M. Varshosaz
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What about GIS?
DTM used as base map similar to 2D DTM is 2.5D since includes third dimension (Z) depending on (X,Y) H stored as an attribute H stored s a function of (X,Y) Digital Terrain Models by M. Varshosaz
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Elements of Digital Terrain Modeling
Tasks involved in DTM production and use.
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DTM tasks: generation
Buy global or national data set Collect data Digital Terrain Models by M. Varshosaz
Buy global or national data set
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Examples Topographic Data
[Eidenbenz et al, 1997] Examples: 3 ENMAs
Current products
OS (GB) IGN (F) SFOT (CH) NCC Paper maps 1:1250, 1:2500 2D database ( 1:1250 , 1:2500 ) National DTM ( 1:10 k,1:50 k) Road centreline DB Paper maps 1:25,50,100,250 k 2D database (acc. 10m) 2.5 D database (acc. 2m) National DTM Road DB Paper maps 25, 50, 100k 2D database (acc. 5m) ( 1:25 k) National DTM ( 1:25,000 ) Paper maps (1/10,000 , 1/25,000 ) DTM of some states (1/25,000 )
Production method
Photogrammetry Map digitizing (*) Map digitizing (*)
Current activity
DB updating by A.Ph. & monoplot. Contours updating by A.Photogr. Map digitizing (*) Photogrammetry Map digitizing (*) Photogr. (*) Map digitizing (*) Map digitizing (*) Photogrammetry Data collection by A.Ph. & D.Ph. Develop prod. line for image matching Develop prod.line for auto road extrac.
Map revision Prepare for upgrading to 2.5 D Develop prod. line for auto AT Develop prod. line for digital OP from auto AT and national DTM Production/Revision (*) completed Digital Terrain Models by M. Varshosaz
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Data capture
Data acquisition techniques Surveying Photogrammetry and Remote Sensing Laser ranging Using current topographic maps Model construction Interpolation techniques Digital Terrain Models by M. Varshosaz
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DTM tasks: manipulation
Modification and refinement of DTMs, and derivation of intermediate models. This might include: Editing: correcting errors and updating DTMs.
Filtering: smoothing, enhancing, compression and Resampling.
Merging and Joining DTMs: combining DTMs from several sources (possibly at different epochs).
Converting DTM from one data structure to another: for example: TIN to grid
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DTM tasks: interpretation
Extraction of terrain related attributes and features through quantitative analysis Geomorphometric analysis DTM quality assessment Error detection Quality control Planning and engineering applications Visibility analysis Digital Terrain Models by M. Varshosaz
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DTM tasks: visualization
Orthographic techniques Contours Hill shading Combination with 2D data Perspective techniques Block diagrams 3D perspective Virtual Fly Digital Terrain Models by M. Varshosaz
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