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I am trying to access the new Bathymetry data published here: http://topex.ucsd.edu/WWW_html/srtm30_plus.html

Is there a way QGIS or similar tool can read these files. Nothing seems to be working, but I am very new to using GIS tools and their rainbow of formats. Any examples or ideas would be appreciated.

Thanks Eric

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3 Answers 3

up vote 1 down vote accepted

These are what, files with a 'srtm' extension? Landserf (free) can load and convert these to something that QGIS can recognise (asc for example). Nick.

http://www.landserf.org/

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You can SRTM30 Plus data with GRASS GIS like this:

r.in.bin -sb input=e020n40.Bathmetry.srtm \
         output=e020n40_topex bytes=2 north=40 \
         south=-10 east=60 west=20 r=6000 c=4800
r.colors e020n40_topex rules=etopo2

See: http://grass.osgeo.org/wiki/Global_datasets#SRTM30plus_data_DEM

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Edit: Actually a much simpler option is to also download the .ers metadata file and just use ArcMap's (tested in v10.2) regular "Add Data" button to select the .ers file.

SRTM30 Plus data can also be open in ArcMap by changing the extension to .bil and creating a text header file with the same filename and a .hdr extension. A working example for the tile w020n40.Bathymetry.srtm would be a w020n40.Bathymetry.hdr file containing the following:

BYTEORDER      M
LAYOUT         BIL
NROWS          6000
NCOLS          4800
NBANDS         1
NBITS          16
PIXELTYPE      SIGNEDINT
ULXMAP         -20
ULYMAP         40
XDIM           0.008333333333333333
YDIM           0.008333333333333333
NODATA         -3.402823e+038

I'm not sure why BYTEORDER M works because the .ers metadata file specifies MSBFirst and this should require the BYTEORDER I, but this doesn't interpret the data properly. Similarly, the GRASS GIS solution by markusN requires the byte swap flag -b.

Further info here: ESRI Help on BIL, BIP, and BSQ raster files

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