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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”

slide8
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

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

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

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

INTAGRAF 2005 – Sabine Schmidt, “Topography and DEM”

topographic correction onshore
Topographic correction onshore

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

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

INTAGRAF 2005 – Sabine Schmidt, “Topography and DEM”

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