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Topography and DEM. Modelling mountains. Topography and DEM. TIN: Vector model (Triangulated Irregular Network). History:Official elevation network had to be used for a 3D model, Can integrate different sources of data, Very flexible, can model even vertical or overhanging topography.

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Topography and dem

Topography and DEM

Modelling mountains


Topography and dem1
Topography and DEM

TIN: Vector model (Triangulated Irregular Network)

  • History:Official elevation network had to be used for a 3D model,

  • Can integrate different sources of data,

  • Very flexible, can model even vertical or overhanging topography

INTAGRAF 2005 – Sabine Schmidt, “Topography and DEM”


Topography and dem2
Topography and DEM

TIN: Vector model (Triangulated Irregular Network)

INTAGRAF 2005 – Sabine Schmidt, “Topography and DEM”


Topography and dem3
Topography and DEM

Raster model (DEM – Digital Elevation Model)

  • Data are sorted in a regular, quadratic grid

  • Ideal for scan-lines of satellites

  • Easy to treat / to implement

  • BUT

  • Contains redundant information in flat areas

    •  can be very large!

INTAGRAF 2005 – Sabine Schmidt, “Topography and DEM”


Topography and dem4
Topography and DEM

Raster model (DEM – Digital Elevation Model)

INTAGRAF 2005 – Sabine Schmidt, “Topography and DEM”


Topography worldwide
Topography worldwide

GEBCO Ocean Mapping at Intergovernmental Oceanographic Commission (IOC)

http://www.ngdc.noaa.gov/mgg/gebco/gebco.html

Topography / bathymetry worldwide complete: 1 Minute academic license : 99 pound sterlingGTOPO30 U.S. Geological Survey's EROS Data Center a compilation of different raster and vector sources, completed in 1996Only onshore data, 30 seconds

http://edcdaac.usgs.gov/gtopo30/gtopo30.aspftp://edcftp.cr.usgs.gov/pub/data/gtopo30/global/ DVD 78 $ FTP download free of charge

SRTMShuttle Radar Topography Mission (NASA, U.S.G.S. EROS Data Center ) Only onshore data between 60° N and 56°S, 3 seconds, in the United States 1 second

Satellite mission: Feb. 11th - 22nd 2000

http://srtm.usgs.gov/

FTP download free of charge

INTAGRAF 2005 – Sabine Schmidt, “Topography and DEM”


Different spatial resolution
Different spatial resolution

INTAGRAF 2005 – Sabine Schmidt, “Topography and DEM”


SRTM

Most frequently used data set

Resolution: 3“ (approx. 90 meters)Height levels: 1 mCoordinates (datum) WGS84Error horizontal (relative): 15 m Error vertical (relative): 6 m available via ftp://e0mss21u.ecs.nasa.gov/srtm/or – using an input scheme - http://seamless.usgs.gov/Data format: .htg or .bil – binary format in files of 1 x 1 degree

Contains data gaps- offshore- in water covered areas- in areas of rough topography

INTAGRAF 2005 – Sabine Schmidt, “Topography and DEM”


Srtm the method i

The fixed baseline interferometry uses the traveltime difference between two radar beams, which are sent to the Earth, reflected at the surface, and then received by two antennas at a distance of 60 m.

SRTM – The method I

60 m

Figures from: http://srtm.usgs.gov/

INTAGRAF 2005 – Sabine Schmidt, “Topography and DEM”


Srtm the method ii
SRTM – The method II difference between two radar beams, which are sent to the Earth, reflected at the surface, and then received by two antennas at a distance of 60 m.

Radar Holograms

Radar Image

Radar Image

Interferogram

+ Phase

Information

+ Phase

Information

Digital Elevation Model

INTAGRAF 2005 – Sabine Schmidt, “Topography and DEM”


Srtm data gaps
SRTM – data gaps difference between two radar beams, which are sent to the Earth, reflected at the surface, and then received by two antennas at a distance of 60 m.

Data Gaps

(here marked red)exist in areas of rough topography or water covered areas.cause problems with- visualization- calculation of the topographic correction- volume and/or surface calculationsMay be filled bya) interpolation, orb) other data (gtopo30)

INTAGRAF 2005 – Sabine Schmidt, “Topography and DEM”


Srtm vertical error
SRTM - Vertical Error difference between two radar beams, which are sent to the Earth, reflected at the surface, and then received by two antennas at a distance of 60 m.

Flat map

Shaded relief

(vertical 6 m relative)causes severe problems in areas with flat topography

INTAGRAF 2005 – Sabine Schmidt, “Topography and DEM”


Terrain correction amounts
Terrain Correction - Amounts difference between two radar beams, which are sent to the Earth, reflected at the surface, and then received by two antennas at a distance of 60 m.

INTAGRAF 2005 – Sabine Schmidt, “Topography and DEM”


Topographic correction onshore
Topographic correction onshore difference between two radar beams, which are sent to the Earth, reflected at the surface, and then received by two antennas at a distance of 60 m.

Histogram of topographic reduction values in percent.

Values of histogram classes given in 10-5 m/s2.

INTAGRAF 2005 – Sabine Schmidt, “Topography and DEM”


Topographic correction offshore
Topographic correction offshore difference between two radar beams, which are sent to the Earth, reflected at the surface, and then received by two antennas at a distance of 60 m.

Histogram of topographic reduction values in percent.

Values of histogram classes given in 10-5 m/s2.

INTAGRAF 2005 – Sabine Schmidt, “Topography and DEM”


Terrain correction radius
Terrain Correction - Radius difference between two radar beams, which are sent to the Earth, reflected at the surface, and then received by two antennas at a distance of 60 m.

INTAGRAF 2005 – Sabine Schmidt, “Topography and DEM”


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