Digital Terrain Models by M. Varshosaz 1 DTM by M. Varshosaz.

Digital Terrain Models by M. Varshosaz

1 DTM by M. VarshosazDTM by M. Varshosaz


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3 An introduction to DTMAn introduction to DTM

Overview of your syllabus Definition Applications Overview of DTM tasks

Generation Manipulation Interpretation Visualizations


4 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.


5 TerminologyTerminology

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).


6 TerminologyTerminology

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.


7 Terminology (cont.)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.


8 Terminology (cont.)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.


9 DTM synonyms: DTM synonyms: conclusionconclusion

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


10 DEM productsDEM products

Slope angle Slope aspect Slope convexity Slope length Hillshading 3D display


11 DTM Application DTM Application DomainsDomains

Civil Engineering: Cut-and-fill problems involved with road

design. Site planning. Volumetric calculations in building dams

and reservoirs.


12

(Rail) Road design(Rail) Road design

Horizontal alignment


13

Conventional (rail)road Conventional (rail)road designdesign

Longitudinal Profile

(vertical alignment)


14

Cross Sections

cut & fill volumes

Concept of

Conventional (rail)road Conventional (rail)road designdesign


15

SCOP

(Rail)road design with (Rail)road design with DTMDTM


16 DTM Application DTM Application domains (cont.)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.


17 Applications of DTM Applications of DTM (cont.)(cont.)

Analysis and interpretation of terrain morphology

A vertical view of a computed drainage system


18 DTM Application DomainsDTM 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.


19

Monitoring waste deposits Monitoring waste deposits comparing volumes under comparing volumes under DTM in different timesDTM in different times

100 m


20 DTM Application DTM Application DomainsDomains

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


21 Applications of DTM Applications of DTM (cont.)(cont.)

Military service 3D visualization

and Flight simulation

Intervisibility analysis

Weapon guidance etc


22 DTM application areas DTM application areas (cont.)(cont.) Surveying and photogrammetry

Orthophoto production Topographic mapping


23 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 H stored s a function of (X,Y)


24 Elements of Digital Terrain Elements of Digital Terrain ModelingModeling

Tasks involved in DTM production and use.


25 DTM tasks: generationDTM tasks: generation

Buy global or national data set Collect data


26

Buy global or national data Buy global or national data setset


27 Examples Topographic Examples Topographic DataData

(*) completed[Eidenbenz et al, 1997]

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 ( 1:10k,1:50k)

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) 2.5D 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 2.5D Develop prod. line for auto AT Develop prod. line for digital OP from auto AT and national DTM

NCC Paper maps (1/10,000 , 1/25,000 ) DTM of some states (1/25,000 )

Photogrammetry Production/Revision


28 Data captureData capture

Data acquisition techniques Surveying Photogrammetry and Remote Sensing Laser ranging Using current topographic maps

Model construction Interpolation techniques


29 DTM tasks: DTM tasks: manipulationmanipulation

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.


30 DTM tasks: DTM tasks: interpretationinterpretation

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


31 DTM tasks: visualizationDTM tasks: visualization

Orthographic techniques

Contours Hill shading Combination with

2D data Perspective

techniques Block diagrams 3D perspective Virtual Fly


32 Your feedback Your feedback

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Digital Terrain Models by M. Varshosaz 1 DTM by M. Varshosaz.

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