Importing Bathymetry Data

dBSea supports several formats for importing bathymetry data:

GeoTIFF - Georeferenced raster images (.tif, .tiff) — recommended
ESRI ASCII grid - Standard GIS raster format (.asc) — recommended
CSV files - Comma or semicolon separated values (raster grid)
XYZ files - Point data with x, y, depth columns (vector — requires conversion)

GeoTIFF Files

GeoTIFF is a widely-used format for georeferenced raster data and is one of the recommended formats for importing bathymetry into dBSea.

To import a GeoTIFF:

Go to Tools → Load bathymetry
Select a GeoTIFF file (.tif, .tiff)

The geographic reference information embedded in the GeoTIFF is used to position the bathymetry correctly.

ESRI ASCII Grid Files

ESRI ASCII grid (.asc) files are another recommended raster format. These files include a header with grid dimensions and cell size, followed by the data values. An advantage of this format is that northing, easting, and scaling data are embedded in the header, so dBSea can set coordinates and scale automatically.

dBSea reads the ncols header parameter to determine row lengths, so rows do not need consistent delimiters.

CSV Files (Raster Grid)

Bathymetry data can be imported from comma separated value (CSV) files arranged as a raster grid — each row represents a row of the grid, and each cell contains a depth in metres. CSV files can be created in Excel or similar programs. Example files may be found in the program directory.

Common CSV Format Issues

As CSV is not a standardised format, there are several problems that may occur, depending on the specific file format. Below we list some problems you may encounter:

Upon loading a CSV file, the program will ask whether the values are separated by commas or semicolons. It will also attempt to guess the correct one.
CSV files created by different programs may use different standards and locale settings. For example, in some regions, 123,45 is used instead of 123.45.
To ensure correct importation of data, use a decimal point as the decimal separator.
Some programs wrap each field in quote marks, like "123.45";"45.6";"42" – this is not supported for import.
Line endings differ by operating system; files from non-Windows machines may cause problems.

File Type Notes

Many .csv files are actually .xyz files or a variation, typically containing three columns: x, y, and depth. These are vector (point) data and cannot be imported directly as bathymetry — they must first be converted to a raster grid using the CSV Editor tool. If possible, obtain the data in a raster format (GeoTIFF or ESRI ASCII grid) instead.
The program requires the same number of fields (delimiters) on each line of the file. This does not apply to ESRI ASCII grid files, where row ends are determined using the ncols header parameter.
If import fails, try opening the file in Excel or LibreOffice Calc and re-saving it as a CSV file.
Very large CSVs may exceed spreadsheet limits. In those cases, use text editors like Emacs, Vim, or Notepad++.

Vector Data (XYZ, Shapefiles)

dBSea can work with vector bathymetry data (XYZ point clouds, ESRI shapefiles), but these formats require an extra conversion step. Vector data must first be converted to a raster grid using the CSV Editor tool, which performs a Delaunay triangulation to produce a regular grid from the scattered points.

If you have access to GIS software (e.g. QGIS, ArcGIS), it is generally better to export your data as a raster format (GeoTIFF or ESRI ASCII grid) before importing into dBSea, rather than relying on the CSV Editor conversion.

Additional Notes on Bathymetry

Null or Missing Values

When importing bathymetry, it’s possible for some pixels to be null, unsurveyed, or marked as NO_VALUE or NaN (not a number).

Types of Bathymetry Input

There are different types of bathymetry data:

Depths only: Land areas are left null. Depths are typically (but not always) positive.
Both depths and heights: Depths are typically (but not always) negative.

A common dataset is GEBCO, which provides global coverage. While convenient, its resolution is sometimes too coarse for detailed work. GEBCO uses negative values for depths.

Heights and Depths Orientation

Some datasets may have heights and depths swapped, showing land where there should be sea, and vice versa. To correct this in dBSea, go to Tools → Swap heights and depths.

From version 3 onwards, dBSea attempts to automatically detect and correct the orientation of bathymetry, especially for known formats like GEBCO.