Point Soundings

• NOAA soundings at  http://maps.ngdc.noaa.gov/viewers/bathymetry/ 
  • Turn on data in "NOS Hydrographic Surveys". 
  • Zoom in on map.
  • Outline box via the Identify button
  • Pick a survey by its ID
  • BAG files can be read via GDAL, and contain very nice grids.  You can download directly.
  • Get sounding data:
    • in XYZ format, which requires making a request and awaiting download directions via email.  Decompress the GZ file, and convert to a DBF file.  Except for the delay to get the data extracted, this is marginally easier to use than the hyd93 format.
    • in hyd93 format (.a93 extension), which is an ASCII file that needs only reading the format metadata and a small amount of cleanup in Matlab or Excel to import as a CSV in MICRODEM.
    • NOAA Soundings probably will not have a minus sign. You should multiply them by -1.

Import to MICRODEM Vector database

• If the file has a header row, the conversion can be done:
  • Open database without map on Main Program Toolbar
  • Database (shapefile) on the Map Window Toolbar

Import to MICRODEM Grids

•   Data Manipulation, Import, ASCII DEMs, DBF or ASCII XYZ (works if there is not a header row in the file).
• Max/mean/min grids from point data: If the sounding density is much greater than what you want, you can get the max/mean/min values in a grid, and decide which value most closely works for what you want to do.

Last revision 11/15/2018