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DTM by M . Varshosaz DTM by M . Varshosaz
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An introduction to DTM An introduction to DTM
Overview of your syllabus
Definition
Applications
Overview of DTM tasks
Generation
M anipulation
Interpretation
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Definition: 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 Terminology
Digital Terrain M odel (DTM ).
Digital Elevation M odel (DEM ).
Digital H eight M odel (DH M ).
Digital Ground M odel (DGM ).
Digital Terrain Elevation Data
(DTED).
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Terminology Terminology
DEM (Digital Elevation M odel):
Generally refers to a regular array of elevations (squares or hexagon).
The term is in widespread use in the USA.
DH M (Digital H eight M odel):
Similar as DEM but less commonly used.
The term originated in Germany.
DGM (Digital Ground M odel):
M ore emphasis on the digital model of the
solid/continuous surface of the earth.
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Terminology (cont.) Terminology (cont.)
DTM (Digital Terrain M odel):
M ore 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 N ational Imaging and
M apping Agency (N IM A) formerly known as the
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Terminology (cont.) Terminology (cont.)
DSM (Digital Surface M odel):
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: DTM synonyms:
conclusion conclusion
M ost 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 (M ODEL)
Data and model stored and worked in digital
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DEM products DEM products
Slope angle
Slope aspect
Slope convexity
Slope length
H illshading
3D display
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DTM Application DTM Application Domains
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 (Rail) Road design
Horizontal alignment
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Conventional (rail)road Conventional (rail)road
design design
Longitudinal Profile
(vertical alignment)
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Cross Sections
cut & fill volumes
Conventional (rail)road Conventional (rail)road
design
design
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SCO P
(Rail)road design with
(Rail)road design with
DTM DTM
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DTM Application DTM Application domains (cont.)
domains (cont.)
Earth Sciences:
Drainage basin network development and delineation.
H ydrological run-off modeling.
Geo-morphological simulation and classification.
Geological mapping.
Generating slope and aspect maps.
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Applications of DTM Applications of DTM (cont.)
(cont.)
Analysis and interpretation of
terrain morphology
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DTM Application Domains DTM Application Domains
Planning and Resource M anagement:
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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M onitoring waste deposits M onitoring waste deposits
comparing volumes under comparing volumes under
DTM in different times
DTM in different times
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DTM Application DTM Application Domains
Domains
M ilitary Applications:
Consumers and producers (e.g., N IM A).
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.
DTM s are useful for various surveying and photogrammetric activities:
Ortho-photo production,
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Applications of DTM Applications of DTM (cont.)
(cont.)
M ilitary service
3D visualization and F light
simulation
Intervisibility analysis
Weapon guidance
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DTM application areas DTM application areas (cont.)
(cont.)
Surveying and photogrammetry
Orthophoto production
Topographic mapping
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What about GIS? 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
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Elements of Digital Elements of Digital Terrain M odeling
Terrain M odeling
Tasks involved in DTM production
and use.
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DTM tasks: generation DTM tasks: generation
Buy global or national data set
Collect data
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Buy global or national data
Buy global or national data
set set
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Examples Topographic Examples Topographic Data Data
Examples:
3 ENMAs Current products Production method
Current activity
OS
(GB)
Paper maps 1:1250, 1:2500 2D database (1:1250 , 1:2500 )
National DTM (1:10 k,1:50 k)
Road centreline DB
Photogrammetry Map digitizing (*) Map digitizing (*)
DB updating by A.Ph. & monoplot.
Contours updating by A.Photogr.
IGN
(F)
Paper maps 1:25,50,100,250 k 2D database (acc. 10m) 2.5 D database (acc. 2m) National DTM
Road DB
Map digitizing (*) Photogrammetry Map digitizing (*)
Data collection by A.Ph. & D.Ph.
Develop prod. line for image matching Develop prod.line for auto road extrac.
SFOT
(CH)
Paper maps 25, 50, 100k 2D database (acc. 5m) (1:25k)
National DTM (1:25,000 )
Photogr. (*) Map digitizing (*) Map digitizing (*)
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
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Data capture Data capture
Data acquisition techniques
Surveying
Photogrammetry and Remote Sensing
Laser ranging
Using current topographic maps
M odel construction
Interpolation techniques
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DTM tasks: DTM tasks:
manipulation manipulation
M odification and refinement of DTM s, and derivation of intermediate models.
This might include:
Editing: correcting errors and updating DTM s.
Filtering: smoothing, enhancing, compression and Resampling.
M erging and Joining DTM s: combining
DTM s from several sources (possibly at
different epochs).
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DTM tasks: DTM tasks:
interpretation 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
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DTM tasks: DTM tasks:
visualization visualization
Orthographic techniques
Contours
H ill shading
Combination with 2D data
Perspective techniques
Block diagrams
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