Wr4-2 Srtm Maps
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Transcript of Wr4-2 Srtm Maps
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Niels G. Mortensen & the WAsP team
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Outline
Introduction to SRTM mission and
How to get SRTM data
Conversion to WAsP maps
SRTM ma s are not et com lete
Pitfalls
Be careful!
WAsP and raster maps
Jan 2012Course 457002 DTU Wind Energy
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Shuttle Radar Topography Mission
Space Shuttle February 2000
Resolution ~ 2525 m2
80% of the Earths land mass
9 terabytes of raw data
r po n e eva ons or every
1 arc-sec (~30 m) for USA
3 arc-sec (~90 m) outside
Vertical accuracy 5-10 m (z)
Unedited and finished data (v 2.1)
Digital Surface Model rather than
Digital Elevation Model
For more information, visithttp://www2.jpl.nasa.gov/srtm/
Jan 2012Course 457003 DTU Wind Energy
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SRTM coverage map
Jan 2012Course 457004 DTU Wind Energy
Colour indicates number of passes by space shuttle Endeavour
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Hand-digitised and SRTM maps
3110
3110
3100
Gulf of Suez
3100
Gulf of Suez
3090
hing[km]
N
NW
3090
hing[km]
N
NW
3080N
ort
Gulf of El-Zayt
3080N
ort
Gulf of El-Zayt
3070 SW
Ras El-Behar 3070 SW
Ras El-Behar
Jan 2012Course 457005 DTU Wind Energy
Easting [km] Easting [km]
Hand-digitised SRTM map
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Example from Portugal
Hand-digitised map SRTM map Wind
StationElevation
[m a.s.l.]
RIX
[%]
Elevation
[m a.s.l.]
RIX
[%]
U10
[m/s]
Port 06 933 25 930 28 4.49
Port 07 982 29 980 33 5.16
Port 08 1047 17 1040 18 6.06
Port 09 1082 9 1070 10 5.84
Port 10 1012 9 1010 11 5.56
Jan 2012Course 457006 DTU Wind Energy
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SRTM and reference maps
Referencezis
by IGeoE
Unedited SRTMprocessed likedescribed above
Spacing of gridpoints is 100 m
Difference iscalculated as =z zref foreach grid pointand coloured, see
.
= 2.5 m
= 5.7 m
Jan 2012Course 457007 DTU Wind Energy
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Map characteristics
Hand-digitised from 1:25,000 maps
50- and 10-m height contours
Contoured from SRTM data (Surfer)
10-m height contours all over
Jan 2012Course 457008 DTU Wind Energy
Spot elevations Spot elevation (mast only) added
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Comparison of WAsP cross-predictions
10
8
9
ps)[ms-1] Up @ 10, 50, 100 m
Y= 0.99 X+ 0.08
7
eed(SRTM
m
5
6
ictedwindsp
3
4Pre
Jan 2012Course 457009 DTU Wind Energy
Predicted wind speed (handmade maps) [ms-1]
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Three sample 20-MW wind farms
Turbine type Gamesa G47 Nordex N62 Enercon E66
Rated power 30660 kW 161300 kW 111800 kW
Hub height 50 m a.g.l. 69 m a.g.l. 67 m a.g.l.
Total net AEP 57.7 GWh 56.8 GWh 58.3 GWh
Ran e [GWh] 1.77-2.17 3.10-3.99 5.11-5.43
SRTM maps* = -0.9% = -0.4% = -1.7%
Range [GWh] 1.76-2.18 3.19-4.07 5.17-5.44
*Details onl addedaround themet. station not the turbine sites!
Jan 2012Course 4570010 DTU Wind Energy
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Transformation to WAsP maps
SRTM grid coordinates are non-projected (latitude, longitude).
or zon a re erence sys em a um s
Vertical reference system is the EGM96 geoid
Transformation of coordinates to metric system
Construction of height contours (vector) from grid data (raster)
Map examples shown above have used
Geo-projection utility or Map editor for coordinate transformation
Surfer 9 (Golden Software) for contouring (see www.wasp.dk)
Other software exist to view and transform SRTM data, such as
Global Mapper 11 (commercial, Global Mapper Software LLC)
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Jan 2012Course 4570011 DTU Wind Energy
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Construction of height contours from grid data
Jan 2012Course 4570012 DTU Wind Energy
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Download SRTM data from web site
http://dds.cr.usgs.gov/srtm/version2_1/ File name-
left (LL) corner of11 degree tile
HGT format iss m ar o eGTOPO30 DEMformat which is
supported by e.g.Surfer
Coastline dataexist as well onweb site (SWBD)
Some void-filleddata sets exist aswell, e.g. CGIAR-CSI 4
Jan 2012Course 4570013 DTU Wind Energy
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SRTM data conversion be careful!
The result is a WAsP ASCII map that can be used for WAsP analysis.
If spikes and voids represent large problems, the more comprehensivemethod described at www.wasp.dk could be used.
Do remember...
that the SRTM elevation data have not been tested in all parts of the.
that when you carry out a WAsP project, you are in charge andresponsible for evaluating the WAsP inputs and the results includingthe availability and quality of SRTM data.
More data sets are coming
ASTER Global Digital Elevation Model
Jan 2012Course 4570014 DTU Wind Energy
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ASTER Global Digital Elevation Model (GDEM)
Earths land surface between 83N and 83S (99%)
Jan 2012Course 4570015 DTU Wind Energy
11 degree tiles in GEOTIFF format, 1 arc-sec resolution (~ 30 m)