Creating depth specific contours from bathymetry data

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Leon
Leon on 24 Aug 2021
Edited: Leon on 24 Aug 2021
The bathymetric data are available through NetCDF, Data GeoTiff and ESRI ASCII raster formats: https://www.gebco.net/data_and_products/gridded_bathymetry_data/#global
What is the best format Matlab can handle? How could I use them to generate contours at a specific depth, say 200 meters?
My ultimate goal is to create land/sea masks so that I can turn data on land to NaNs. Such masks would require the the lon lat pairs to be in a closed loop, i.e., the starting lon lat pair needs to be identical to the ending lon lat pair. Depending on the locations, multiple such loops would needed, e.g., one island would need to have its own lon lat loop.
It is my first time to process bathymetric data, and any tips would be greatly appreciated.
Many thanks!

Accepted Answer

KSSV
KSSV on 24 Aug 2021
You can save the file in the .nc format. MATLAB has functions like ncdisp to view the conntents of nc file and ncread to load the variables. Once you have lon, lat, depth into workspace; you can use contour to get your depth related contours,
If X, Y, Z is your data.
h = contour(X,Y,Z,[200 200]) ; % you need to mention levels in contour
  1 Comment
Leon
Leon on 24 Aug 2021
Many thanks for the recommendations!!
How do I extract the longitude and latitude information out of the generated contour?
Is it possible to generate shape files out of the created contours? My ultimate goal is to create land/sea masks so that I can turn data on land to NaNs. Such masks would require the the lon lat pairs to be in a closed loop, i.e., the starting lon lat pair needs to be identical to the ending lon lat pair. Depending on the locations, multiple such loops would needed, e.g., one island would need to have its own lon lat loop.

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