Bathymetric contour
veronika
Global Mapper User
Hello, I am trying to generate bathymetric contour from SRTM worldwide elevation data (online data source from Global Mapper), but I only get contours with positive value, and I need also negative ones. Can anyone help with the steps or suggestions.
Thank you
Thank you
Comments
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Do you want bathymetric contours? The SRTM terrain data doesn't have bathymetry, so the only place you would get negative contours would be some place with elevations under sea level, like Death Valley or near the Dead Sea.
Thanks,
Mike
Global Mapper Guru
geohelp@bluemarblegeo.com
Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation -
Thank you for the replay. Yes, I need bathymetric contours of the ocean, around Haiti island, and so far I could not find where to generate from or digitize from a topographic map with contours.
Veronika -
Veronika,
If you visit ftp://topex.ucsd.edu/pub/srtm30_plus/srtm30/data/ you can get 30-arc-second resolution global data that includes bathymetry. If you don't need a lot of detail then then w100n40 tile should cover Haiti. You can generate bathymetry contours from that.
Thanks,
Mike
Global Mapper Guru
geohelp@bluemarblegeo.com
Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation -
I had this exact problem, yesterday. The data contains water depth, which has to be positive. I need to convert the numbers to negative values to become the "sea floor". Any suggestions. I could open the file with Manfield's Kedit and insert a "-", but like to do the work inside Global Mapper.
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If you have a grid loaded where depths are positive, just open the Options dialog for the layer and on the Alter Elevation Values tab provide a scale factor of -1 which will invert the values. Then create your contours.
Thanks,
Mike
Global Mapper Guru
geohelp@bluemarblegeo.com
Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
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