1. Digital Terrain Models by M. Varshosaz
DTM by M. Varshosaz
Digital Terrain Models by M. Varshosaz
DTM course, M. Varshosaz, Mehr 1379

2. Digital Terrain Models by M. Varshosaz

3. Digital Terrain Models by M. Varshosaz
An introduction to DTM
Overview of your syllabus
Definition
Applications
Overview of DTM tasks
Generation
Manipulation
Interpretation
Visualizations
Digital Terrain Models by M. Varshosaz
DTM course, M. Varshosaz, Mehr 1379

4. Digital Terrain Models by M. Varshosaz
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.
Digital Terrain Models by M. Varshosaz

5. Digital Terrain Models by M. Varshosaz
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).
Digital Terrain Models by M. Varshosaz

6. Digital Terrain Models by M. Varshosaz
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.
Digital Terrain Models by M. Varshosaz

7. Digital Terrain Models by M. Varshosaz
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).
Usually refers to girded/regular arrays.
Digital Terrain Models by M. Varshosaz

8. Digital Terrain Models by M. Varshosaz
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.
Digital Terrain Models by M. Varshosaz

9. 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

10. Digital Terrain Models by M. Varshosaz
DEM products
Slope angle
Slope aspect
Slope convexity
Slope length
Hillshading
3D display
Digital Terrain Models by M. Varshosaz

11. DTM Application Domains
Civil Engineering:
Cut-and-fill problems involved with road design.
Site planning.
Volumetric calculations in building dams and reservoirs.
Digital Terrain Models by M. Varshosaz

12. Digital Terrain Models by M. Varshosaz
(Rail) Road design
Horizontal alignment
Conventional approach: use topomap 1:50,000 to figure out initial alignment
Digital Terrain Models by M. Varshosaz
DTM course, M. Varshosaz, Mehr 1379

13. Conventional (rail)road design
Longitudinal Profile
(vertical alignment)
Set out horizontal alignment and survey -> design long. profile
Digital Terrain Models by M. Varshosaz
DTM course, M. Varshosaz, Mehr 1379

14. Conventional (rail)road design
Cross Sections
Survey cross sections -> compute cut and fill
cut & fill volumes
Digital Terrain Models by M. Varshosaz
Concept of
DTM course, M. Varshosaz, Mehr 1379

15. (Rail)road design with DTM
SCOP
Digital Terrain Models by M. Varshosaz
DTM course, M. Varshosaz, Mehr 1379

16. 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.
Digital Terrain Models by M. Varshosaz

17. Applications of DTM (cont.)
Analysis and interpretation of terrain morphology
A vertical view of a computed drainage system
Digital Terrain Models by M. Varshosaz

18. 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.
Digital Terrain Models by M. Varshosaz

19. Digital Terrain Models by M. Varshosaz
Monitoring waste deposits comparing volumes under DTM in different times
100 m
Digital Terrain Models by M. Varshosaz

20. 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,
Data quality assessment, and
Digital Terrain Models by M. Varshosaz

21. Applications of DTM (cont.)
Military service
3D visualization and Flight simulation
Intervisibility analysis
Weapon guidance
etc
Digital Terrain Models by M. Varshosaz

22. DTM application areas (cont.)
Surveying and photogrammetry
Orthophoto production
Topographic mapping
Digital Terrain Models by M. Varshosaz
DTM course, M. Varshosaz, Mehr 1379

23. Digital Terrain Models by M. Varshosaz
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

24. Elements of Digital Terrain Modeling
Tasks involved in DTM production and use.
Digital Terrain Models by M. Varshosaz

25. Digital Terrain Models by M. Varshosaz
DTM tasks: generation
Buy global or national data set
Collect data
Digital Terrain Models by M. Varshosaz
DTM course, M. Varshosaz, Mehr 1379

26. Buy global or national data set
Digital Terrain Models by M. Varshosaz
DTM course, M. Varshosaz, Mehr 1379

27. Examples Topographic Data
I have compiled here information collected from 3 sample NMAs - what do they do on satisfying GI users, using efficient technology and copying with their constraints? …
We notice quite some differences, not so much in the products, but certainly in the methods.
[Eidenbenz et al, 1997]
(*) completed
Digital Terrain Models by M. Varshosaz
DTM course, M. Varshosaz, Mehr 1379

28. Digital Terrain Models by M. Varshosaz
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

29. 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 conversion.
Digital Terrain Models by M. Varshosaz
DTM course, M. Varshosaz, Mehr 1379

30. 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
DTM course, M. Varshosaz, Mehr 1379

31. 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
DTM course, M. Varshosaz, Mehr 1379

32. Digital Terrain Models by M. Varshosaz
Your feedback
Through your reports, term papers, critics
Digital Terrain Models by M. Varshosaz
DTM course, M. Varshosaz, Mehr 1379